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SB-12 Cabinet Restoration - part 3


Nov 13, 2016
SB-12 Cabinet Restoration - part 3

  • Reassembly (top)


    Tools (top)


    Having the right tools for the job can make a big difference in how well a project turns out. A restoration doesn't require a lot of expensive tools, but it helps to have good ones.

    • A random orbital sander makes the work a lot easier. Hours of hand sanding can be done in minutes with one of these. A sanding bloc can be used on surfaces that a sander can not get into. Surface preparation before affixing the vinyl is important. Some coarseness in the final finish is necessary to allow the glue to adhere well into the wood. A rougher surface allows the glue to Bite into the wood. Too rough and the contact with the vinyl will be reduced. I recommend that the wood be final sanded with at least 320 Grit sandpaper and no finer than 220 Grit when using a random orbital sander. Hand sanding tends to be less Aggressive when a very light touch is used.

    • A glue has to be chosen. There are a variety of products to use. Some details have been presented in the technical cabinet section. Two of the most popular alternatives are water and solvent based contact cements. They are both available at hardware stores. They both have their advantages. Both offer bonds that are stronger than the wood. If you attempt to remove the vinyl there will be a lot of wood tearing away. The water based contact cement is what is commonly sold as Tolex Glue by suppliers that sell cabinet vinyl. If forms a very strong bond with the vinyl and is non hazardous to use. Being water based, it cleans up easily and is non toxic to the environment. This is advantageous if you are working indoors. The solvent based contact cement offers a stronger bond, more than need for this application. It is also a little less forgiving when you are working. Once the surfaces come into contact it is difficult to reposition the vinyl if necessary. The fumes from the solvent in the cement are very strong and toxic and remain so until they fully evaporate. There is some off gassing that continues after the cabinet is covered. I prefer the water based contact cement but use the solvent based one in situations where a very strong bond is required. For example, on a back panel of an amp that is right next the power Tubes where I'm concerned that there may be vinyl shrinkage or peeling of the edges, I would use the solvent based product.

    • Paint brushes, a glue spreader, or a small nap adhesive roller can be used to spread the glue. A sprayer makes live easier. A cabinet is covered in multiple stages, one or two surfaces are typically done at a time. Brushes and spreaders should be cleaned between applications. Some brushes need to be replace once they have been used once, other can be cleaned and combed out between usages. Metal combs for cleaning brushes are available at paint stores. You don't want dried glue lumps from a brush getting under the vinyl, the cabinet surfaces will not look smooth. Change the brush between glue applications if necessary. Inexpensive brushes have a tendency to shed bristles so comb out and remove any Loose ones before you begin. A single bristle under the vinyl can leave a lump on the surface. Care must be taken when using a brush. A rubber or plastic glue spreader is the best way to go for larger surfaces. This method is fast, allows you to spread an even layer of glue, and is cleaner than using a brush. There is much less of a chance of getting lumps on your surfaces. For small surfaces, a brush works well at getting the glue just where you want it. A 4" foam roller does a good job at spreading the glue quickly and ensuring an even coat. It will still be necessary to use a brush to get into small areas where the roller can not get into. A gallon paint can can be used to store the roller and brush when they are not being used. This stops them from drying during the job.

    • Latex rubber gloves are good to wear when working with the glue. Change the gloves as necessary to keep things Clean.

    • A J-roller used for laminate work is indispensable when it comes to pressing down the vinyl onto the cabinet to ensure good adhesion. It can flatten Air bubbles and smooth small lumps under the vinyl.

    • A Thick bladed putty knife can help you get into smaller corners to press down the vinyl. It also makes a good straight Edge for trimming the vinyl in Tight spaces.

    • A good straight Edge that is sized right for the job allows you to make single straight cuts. You want the ruler to be longer than the piece of vinyl.

    • A center head tool and square is useful for finding 45 degree angles such as on the face from of an amp and for checking that surfaces are square. Unfortunately, the corners of some face frames on Portaflex amps are not Cut to a perfect 45 degrees. This tool will allow you to gauge that. Unlike new cabinet builds, some of these old amps are Funky and have quirks that you need to work around. Things are not square, surfaces are not smooth, edge Round over can vary. If the face frame, for example, isn't Cut at a perfect 45 degrees, you need to work with what you have and cut the vinyl accordingly.

    • One of the best investments in this type of work is a good box knife. A handle that is comfortable in your hand will allow you to make straight cuts in the vinyl all the way through. Second passes that can lead to wavy lines. A good supply of blades is also important. For critical cuts, it is good to use a fresh sharp blade each time. Change those blades often!

    • A metal finishing hammer and small 2 lb anvil is useful for straightening nails, nail heads, and flattening metal corners.

    • A rubber mallet us useful for seating metal corners before they are nailed into place.

    • A magnifier such as an Optivisor can help you see details better.

    • Good lighting and an ergonomic work space is important. If you can't see well, lines won't won't be cut straight, details will be missed. You have to be able to get right over the work. Being comfortable while you are working allows you to pay more attention to the details and helps get things right.
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    glue spreading trowels

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    Random orbital sander

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    Sanding bloc

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    Straight edges

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    Laminate J-roller

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    Center head tool on the left is normally used to find the center of a circle. It can be used to find a 45 degree angle.

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    Putty knife

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    Wide putty knife used for wall paper work has a thicker metal blade

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    Box knife

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    Single edge razor blade

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    Metal work finishing hammer

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    Small 2 lb anvil

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    Rubber mallet won't damage metal parts.

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    Optivisor to clearly see what you are working on.

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    4" foam roller. Check on the package to ensure that it is suitable for adhesive application.

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    A paint container can be used to keep the roller and brush in so they won't Dry up when not in use during the job.

    Overview: Applying Blue Check Vinyl(top)


    This tutorial is intended to be a guide showing how it can be done. I can't stress enough that it is important to think through each step and make sure that each step and the placement of the cuts make sense. Don't just follow this guide blindly. I find it helpful to practice doing corner cuts and any other difficult parts first with small scrap pieces of vinyl taped into place instead of glue. If you don't have vinyl scraps, use paper. Do it enough times until you are confident in what you are doing before proceeding. Practice does make perfect.

    I've covered many different types of amps and I can tell you that applying blue check vinyl well to an Ampeg cabinet is about as difficult as it gets. Getting all the checks to align properly takes some balancing when positioning the vinyl to optimize the alignment of the pieces everywhere on the cabinet. Adjust an edge on one side than the other side moves out of alignment. For instance, if you are covering the lid, ideally you want a Full check starting on the top front and back long edges, as well as the left and right side top edges. That can be hard to do if the wood dimension is not an integral number of squares or if the cabinet opening is out of square. You also want the lid squares to align with the squares in the vinyl on the top front and top back rails of the cabinet. You want the squares on the front of the cabinet to run down along the front edges. The cabinet is dimensioned so that the squares align pretty closely. It's never perfect. Getting it right is hard enough with a new cabinet, but older cabinets can be out of square and it's even harder to position the vinyl so that everything matches.

    It's all in the details and when it is done properly, it all comes together. To illustrate, below are some of the critical alignment positions on double baffle B-15N cabinet. Images are courtesy of Mark at Vintage-Blue and this is the alignment that you want to aim for.

    The cabinets with the cutaways aren't some new type of porting, although they would make a nice guitar cabinet. Mark wanted to see what the speaker to transformer clearance would be when the lid is flipped down with different speakers in place.


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    The squares of the lid align with the top front and back of the cabinet.

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    The left and right side cabinet top squares align with the front and back top surfaces. Squares start on an edge.

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    The lid squares align with those of the cabinet.

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    The squares on the front rails start and end on the edges.

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    The squares are perfectly aligned along the edges.

    There are different ways to lay out the vinyl on a cabinet. On the vintage B-15N double baffle cabinets, Ampeg used six pieces of vinyl which required more seams. Mark uses a single piece of vinyl for the back and sides of the cabinet, eliminating two seams on each side of the cabinet. It is such a small detail but the end result is much more esthetically pleasing to the eye. The concept has been adopted by both Loud and Fliptops, as well as many who have recovered their own cabinets.

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    On the right is the vintage Ampeg layout for a B-15N double baffle cabinet, the Vintage-Blue layout is shown on the left.

    SB-12 Vinyl Application (top)

    In this section, we will go through the steps of applying the vinyl onto the SB-12 cabinet. A lot of effort went into preparing the cabinet. The glue was removed, damage was repaired, and the surfaces were sanded. The better the job, the better the vinyl is going to look.

    Squaring the Vinyl (top)

    It is important to check the squareness of the vinyl and cut straight edges to work with. I often lay the vinyl out on a hard floor because I need a large flat surface area to work on. Don't walk on the vinyl, you can stretch it. Although the Ampeg check vinyl has squares on it making it look square, the vinyl can be stretched. You need to check it carefully with a straight edge and be aware of any deficiencies in the material that you might need to work around when cutting pieces out. In some cases, you can cut pieces around any stretches. In other cases, it is going to mean that the checks are not going to align on the cabinet as you want them. In this case you can shift the position of the vinyl by fractions back and forth to allow you to decide on the best compromise position to affix it. Sometimes it takes some time to find the best balance in terms of the position. Try not to over think things. The vinyl layout is hampered by the fact that old cabinets often have issues. They can be out of square, edges can be out of Round, surfaces can be wavy. Any issues can be minimized at the wood preparation stage with the help of wood filler and epoxy. I can't stress the importance of the wood preparation stage.

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    Cutting the vinyl square.

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    Checking lines in the vinyl with a straight edge to ensure that it is not stretched.

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    Marking a location on the vinyl to cut along a line.

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    Long straight edges used for squaring and laying out the vinyl.

    Marking the Vinyl (top)

    It is helpful to mark lines on the vinyl where the cabinet will be positioned, where cuts will need to be made, where areas will be trimmed, where the adhesive will be applied, and even any notes or measurements. A fine tip felt pen does a good job, the markings can be easily seen.

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    Back and Sides (top)

    In this case, a single piece of vinyl is being used to wrap the back and sides of the cabinet. Starting with the biggest area to cover is good approach and lays the foundation for the pieces that are added after. The smaller pieces will integrate onto the cabinet more easily ones the larger surfaces have been covered. The vinyl has been squared, the position it will be on the cabinet has to be decided. Key alignment edges were described in a previous section. Ideally, the edge of a square on the vinyl will be aligned with the top, bottom, left, and right edges of the back of the cabinet. When wrapped around the sides and the front left and right front frame, the edge of a row of squares should align with edges on the cabinet. It is never perfect but this is where the micro-adjustments come into play. The back surface of the vinyl needs to be marked for positioning the cabinet so that everything aligns as best as possible. At this point you are wishing that you were working on a newly constructed cabinet where everything is perfect.

    When all the markings indicating where the cabinet will go on the vinyl have been made, lay the vinyl on a flat surface and place the back surface of the cabinet onto the vinyl, aligned with the marks. Check and double check everything. Then using a marker and straight edge, draw lines around the outline of the cabinet, note where the front and back are. Remove the cabinet and using a long straight edge, extend the horizontal and vertical cabinet outline lines. These will coincide with the cabinet's edges.

    One remarkable point is that the cabinets are sized to fit the check vinyl perfectly. Edges of the cabinet line up with squares on the vinyl pretty well. In the case of the B-15, the cabinet was originally designed with random navy flair basket weave vinyl, no checks on the vinyl. It was a lucky coincidence that the squares all align pretty closely when they switched over to the blue check vinyl.

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    Cabinet positioned and lines drawn on the vinyl

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    Cabinet outline lines are extended with a straight edge.

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    Check and recheck the lines.

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    In this case, a solvent based contact cement was used. A very important point, make sure that the cabinet is wiped down and all dust removed. Clean it with a solvent to remove any oils. Ensure that the vinyl has no foreign matter such as dust or even hair on it. Start spreading the glue on the wood. It is more porous than the vinyl and will soak into the wood. Follow the product directions. In some cases, a second coat of glue may be needed. It is important to spread the glue evenly and not have ridges at the edges. Ridges can Dry and leave a lump under the vinyl. A rubber glue spreader was used to spread the glue. Work the glue into the wood and keep the coat even.

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    Both surfaces must receive a coat of glue. Spread the glue onto the vinyl that will mate with the back of the cabinet.

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    Drying time will vary depending on the temperature and the humidity. A fan can be used to help the drying process.

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    This is where the markings on the vinyl come in handy. The vinyl should be placed on a hard flat surface. Place the cabinet on the vinyl at the edge of the bonding surface. Make sure that it is carefully aligned. Slowly roll the cabinet onto the vinyl, mating the surfaces. Flip the cabinet over and use the J-roller apply pressure to press the vinyl onto the cabinet. This ensures good adhesion. Start in the center and move outward. Use the roller to even out any bubbles or lumps.

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    This first surface is critical. It doesn't hurt to use a straight edge to verify that the squares in the vinyl are aligned with the cabinet edge and that the vinyl is positioned as you want it.

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    The next step is to glue the sides. The adhesive needs to be applied into the leading glued edge where the vinyl is already mated to the cabinet.

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    Where ever there is a seam in the covering. It helps to stain the wood so that it doesn't show through if the vinyl pulls back with time revealing what is underneath. You can see the blue stain that was applied. A marking pen or ink can be used on the wood.

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    Follow the same procedure as before, applying the glue to the wood first and spread it evenly.

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    Apply the glue to the vinyl. The extended lines that were drawn earlier will provide you with a boundary when applying the glue.

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    Wait for the glue to dry as per the product instructions. One Test to determine if it is dry enough, a piece of paper should not stick to the glue.

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    Carefully roll the cabinet onto the vinyl.

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    This is what it should look like.

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    The guide lines that were drawn were useful for determining where the glue should have been applied. Everything looks nice and straight. So far so good.

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    Then use the roller as before. Pay particular attention to the edge. Make sure that there are no lumps. If there are any, attempt to roll them out. The glue is still soft enough to be Compressed with the roller. Applying lots of force will help. The long handle on the J-roller allows you to do this.

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    Follow the same procedure on the other side.

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    The left and right face frames are ready.

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    So is the cabinet top. It is easier to mark the vinyl for trimming and gluing guides once it is on the cabinet. The markings will be more accurate.

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    The vinyl is ready for trimming.

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    Here are three views of the cabinet with the vinyl attached to the back and the sides.

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    The vinyl is well adhered to the cabinet.

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    The vinyl is smooth and there are no lumps. Note how the checks run at a perfect 45 degree angle. A sign that the vinyl is on square along the horizontal cabinet edges.

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    Another verification that the blue checks are aligned with the horizontal edge of the cabinet. This tells you that all the hard work has paid off and it is looking good.

    Trimming the Vinyl (top)

    There are now flaps at the top and the bottom of the cabinet. These will be trimmed and folded over to cover the top back and sides, the left and right face frame, and the bottom outside edges. It is important that there is enough vinyl to cover these surfaces so plan for this when you are sizing the vinyl. It's better to cut the vinyl a little larger and trim it down to size. Trim it initially, then trim it again when gluing. This is where careful planning comes in at the early stages and everything is thought through.


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    Cuts are made along the initial vertical cabinet lines that were marked on the vinyl. Make these cuts on a flat surface using a ruler as a straight edge guide.

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    This is the bottom of the cabinet. The flaps will be used for three sides of the outer edge of the bottom. The center of the bottom will be filled with another piece of vinyl that will also cover the bottom of the face frame. If you are short of vinyl and have to use a stretched out piece, reserve it for this bottom piece.

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    These are the back, right side, and right face frame flaps. The are pre-trimmed and ready for the final trimming.

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    Here is a view of the bottom of the cabinet showing how the flaps should be trimmed. The flaps from the back, sides, and left and right face frame have been trimmed.

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    A view of the side flap and how it was trimmed. Note that a rectangle of vinyl has been removed from each end.

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    Another view of the cuts that were made along the lines that were drawn on the vinyl at the beginning when the back was outlined and the lines were extended.

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    Preparing to cut the top flap that will fold over the side.

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    The straight edge of a ruler is used as a cutting guide. The cabinet is placed on a surface and the ruler placed alone the inner edge of the cabinet top. It is important to use a sharp blade on a cut like this. If the cut isn't accurate, wood which should be covered will show along the edge. Hold the knife against the edge of the rules. Use just enough pressure to cut the vinyl. If you apply too much pressure you risk getting a wavy line. Remember change your blade often so that it cuts easily.

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    The same is done on the other side. Depending on if you are left or right handed, cutting one side will be easier than the other because of the Tight space that you are working in. Good lighting is important, use a magnifier if necessary. Fold up the vinyl to see how well the cuts were done.

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    The next step is to trim the vinyl of the center fold to size. It needs to wrap around the top side edge and extend just into the gasket trough. Use a straight edge to mark the cut lines.

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    Cut with the aid of a straight edge. Note that a scrap piece of plywood, big enough to put the cabinet on, is being used as a scrificial cutting surface to protect the table.

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    The piece of vinyl has been removed.

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    The front edge has also been trimmed. This will be glued to the side of the cabinet. It needs to be extend just beyond the top of the cabinet as shown. More on this later.

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    The same procedure is performed on the other side of the cabinet. Trimming is a multistage process. Once one line is cut, the vinyl lies flat enough to make the next cut. There are a lot of cut and a lot of details. Plenty of chances to make a mistake. Don't work when you are tired.

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    Both side have been prepared for the next stage, the lid surround.

    Lid Surround (top)

    The next step is to glue down the left and right sides of the lid surround.

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    Fold the vinyl over for one last Test fit. Blue painter's tape can be used to frame the gluing surface. Apply the glue and then remove the tape immediately afterwards. You will have a nice straight glue line.

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    When the glue has dried on both surfaces, press down the vinyl.

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    The J-roller can be used here to mate the surfaces but it can't get in at the edges. This is an example where the putty knives can be used to press the vinyl.

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    The vinyl needs to be trimmed to the outside edge of the gasket trough. The trough can serve as a guide. Cut slowly so that the line is as straight as possible. This is a location that catches your eye when you look inside the cabinet. The cut line needs to extend beyond the trough to the inside edge of the cabinet opening. This extended cut should be made using a short ruler as a guide to ensure that it is straight.

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    Gluing down the left and right sides is complete.

    Face Frame Left and Right Sides (top)

    The front of the cabinet has a frame that extends from the outer edge of the cabinet to the baffle. This face frame, much like a picture frame with a 45 degree miter at the corners, is an interesting characteristic of the Portaflex amps. The vinyl that was wrapped around the cabinet's back and sides extends to cover the left and right face frame and wraps into the cabinet where the baffle sits.

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    The cabinet is positioned on its right side with the vinyl flap laying flat on the work surface.

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    The vinyl will be trimmed so that it can be wrapped around the frame into and around the opening of the cabinet.

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    This horizontal cut is about 1/4" larger than the opening. It will be trimmer again later. The same is done for the vertical cut.

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    The excess vinyl in the corners is cut away allowing the flap to be folded.

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    The flap can now be folded into the cabinet. It is a bit over sized. This will be necessary later when a 45 degree cut in the vinyl is made in the mitered corners of the frame. The vinyl needs to extend beyond the 45 degree miter in the wood.

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    The folded in flap.

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    The same cuts are made on the left side.

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    The small corner flap in the middle can be trimmed. It will be cut Parallel to the miter but extending beyond it.

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    The middle flap has been removed. It is best to remove what doesn't have to be there. The vinyl is more manageable that way and it helps to define the gluing boundaries.

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    One last test fit.

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    Time to apply the adhesive.

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    The left face frame. The vinyl extends beyond the miter, it also extends slightly over the adjoining face frame, and it wraps into the cabinet.

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    The same is done on the right side. Note that the adhesive was not applied onto these extended areas as they will be trimmer later when the top and bottom face frame pieces are installed.

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    This is the top of the face frame. Note that, in this case, the corner at the bottom right in this image wasn't trimmed. It could have been.

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    The left and right face frames have been completed.



    Cabinet Top (top)


    Next the rear top will be completed.

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    The vinyl is wrapped around the rear cabinet top in the shape of an inverted U, the back piece extends upward and onto the top and down into the cabinet. There are two small flaps of side vinyl that cover each end.

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    With the back piece folded over, excess material folds into a flap. This gives an indication as to where a cut can be made.

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    The question is, where should the flap be located. The wood rounds over. The cut is best made down the side below the round. How far down the cut is made is a judgement call. A seam along a square edge looks better than a seam in the middle of a square but you don't always have a choice.

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    Stand the vinyl up and prepare for a cut.

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    In this case, it was decided to place the cut just below the top round of the edge. Be careful how long the cut is, it is better to cut it a little shorter, fold the vinyl over the top and see if there is a fold bulging out like what was seen before the cut. If there is a Bulge folding out, continue the cut a little further. Fit it as you go. If you look at the images in the disassembly section, the cut is positioned where it was on the original cabinet. This shows why it is important to document your work as it progresses with a camera. There are so many details that need to be remembered. Don't think that you'll remember them all.

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    Make the cut.

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    It is best if the cut is Parallel to the lines of the checks in the vinyl. One way to do this is to use a jig. A small piece of brass angle can be used. Using a jig will allow all four cuts, front and back, left and right side, to be made a consistent distance from the top of the cabinet. Standardizing the cut is a small detail but it makes the work look better.

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    Brass angle can be used to make a jig to cut against. This is an example of a very basic jig.

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    The problem with a brass angle is that the end of the cabinet may not be level. A better jig would include a plate with a larger surface area that lies along on the top of the cabinets wood rail that you are covering. This would offer better stability to define the cutting angle. Making a jig isn't that difficult. An advantage of brass is that pieces can be glued together with cyanoacrylate adhesive. No fancy machining is necessary. Here is an example of a jig that was made by gluing together a piece of 1/2" brass bar and 1/2" by 4" by 4" plate.

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    The plate offers more stability because of the larger surface area when laid down on top of the cabinet wood frame than the simpler brass angle. The angle jig is simple, the plate jig is more complex. A plate longer than 4" would be an improvement. Another plate that forms a right angle with the one on the top and goes down the back surface of the cabinet would be even better. There are always tradeoffs when it comes to techniques and tools. If you did this sort of work more often, a properly designed jig that could be used on a variety of different cabinets would be worth the investment in time to build.

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    See how the material folds.

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    Adjust the cut until it folds flat.

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    Trim the material using the blade to make a straight cut.

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    Apply the adhesive and fold the vinyl over. Use a putty knife to press the vinyl down.

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    Use the roller along the long edge.

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    In this case, a top flap of vinyl overlays the vinyl on the side. The solvent based contact cement that was used ensures a strong bond that won't lift. An alternative would have been to use a butt joint. We will see how to do this in the next section. The advantage of this type of joint is that it lies flat and there is no bump caused by the overlap. There is nothing wrong with an overlapping joint. The original cabinets had them so they are keeping with tradition. This was the most cost effective way to build them.

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    The back top is completed.

    Cabinet Bottom (top)

    With the flap of vinyl on the top out of the way, the cabinet can be flipped over and the bottom of the cabinet can be done. Here a butt joint is used. This is where two pieces of vinyl meet at their edges. The two pieces of vinyl are overlaid and a single cut is made through both pieces of vinyl. A piece from the top and the bottom are removed and the two remaining pieces of vinyl match perfectly along the cut edge. Both lie flat against the cabinet and there is no overlapping of the vinyl. The seam looks much neater because there isn't a bump. A butt joint is a little more difficult to do than an overlapping joint but looks much better as you will see. Examples showing how to make these joints are available on YouTube.


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    As has already been shown above, cuts are made along the initial vertical cabinet lines that were marked on the vinyl. Make these cuts on a flat surface using a ruler as a guide.

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    The flaps will be used for the outer edge on three sides of the bottom. The center of the bottom will be filled with another piece of vinyl that also will cover the front bottom face frame. If you are short of vinyl and have to use a stretched out piece, the bottom is a good place for it.

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    The three flaps are trimmed square to the desired length. Note the arrows on the top right flap. The triangle of vinyl at the end will be cut away in creating the butt joint. The arrows indicate a line where glue should not be placed. Not having it there makes the joint easier to create.

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    All six corners at the ends of the three flaps will be removed so they should not be glued. The other sections of the vinyl have been glued into place. With contact cement, when the two glued surfaces come into contact, they bond. Care has to be taken to ensure that this doesn't happen when you are in the process of cutting the butt joint. One way to do this, is to apply the glue everywhere except where the joint will be cut and on the vinyl flaps that will be removed. Once the joint is cut, the glue can be applied to the remaining areas.

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    Now for the butt joint. A straight edge is used to make a 45 degree cut from the corner of the cabinet to the inner intersection of the vinyl flaps. This is where the center head tool that was described earlier can be used. It is important that both layers of vinyl are cut in one pass.

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    The outer vinyl triangle is removed.

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    The top piece of vinyl is carefully lifted and the triangular piece underneath is removed.

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    Adhesive is applied to any areas along the edge of the joint that were not glued earlier. When dry, the vinyl is pressed down. You have to look very carefully to see the seam.

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    The same procedure is performed on the other corner.

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    Here's a helpful pointer: Let the contact cement dry only partly for around ten minutes. Lightly overlay the pieces of vinyl, do not press them down, and then make the butt joint cut. After the cut is made, you can carefully lift the pieces and let them dry to the touch. Then press them together. When the contact cement is not dry, the pieces do not adhere fully when they come into contact with each other. This is a technique that you want to try with some scrap pieces and be comfortable with before trying it on the cabinet.

    Another technique when doing a butt joint is to first apply the adhesive everywhere that is to be glued on both surfaces. When the glue is dry, lay down a one inch strip of kitchen parchment or waxed paper, both will work, on the cabinet where the cut will be made. The key here is that the glue will not stick to the paper and the paper acts a barrier preventing the glued surfaces from adhering. Press down the vinyl everywhere except where the parchment paper is. Make the cut through the two layers on vinyl and the paper, lift the layers and remove the pieces of vinyl and the paper, press down the vinyl. This technique works very well and makes it easier to cut the joint.

    It is very important that only a single cut is made. With more than one pass of the blade, you risk cutting out slivers of vinyl and the joint will not mate perfectly. There will be a space in the seam with no vinyl. If this happens, don't worry, you can try stretching the vinyl as you close the seam, or you can fill it with tinted cyanoacrylate glue afterwards. Use a sharp blade to make the cut and apply even pressure. Cut slowly and carefully. It never hurts to try making a few practice cuts on some scrap pieces before trying it on the cabinet.

    Face Frames: Top and Bottom (top)

    The next two vinyl pieces up are the top face frame and bottom face frames. The top face frame includes the top front rail, the bottom face frame includes the center portion of the bottom of the cabinet. The positioning of these pieces is very important. The squares have to be aligned with the main piece of vinyl that wraps around the back and sides. When you look at the amp, your eye is drawn to the face frame. It's the first thing that you notice. You want the squares of the top and bottom faces to align with the left and right. Attention to detail in getting the vinyl's placement correct, left and right, up and down, is very important at this point. Cabinet dimension variations mean that a perfect alignment isn't always possible but often you can get pretty close.

    Butt joints will be used to keep the lines on the cabinet clean. We will start with the bottom face frame.

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    The vinyl is squared and trimmed and the guide lines are marked. The adhesive is applied.

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    This is the bottom left side. Note how the vinyl is positioned so that the lines of the squares align with those of the left face frame. Exactly the way that you want it to look.

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    The bottom right side. Again the squares align.

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    The bottom face frame is attached. Note how it aligns.

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    The gluing boundary lines are in place for the bottom section.

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    The vinyl is pressed onto the bottom of the cabinet and the lower front face frame.

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    Prepare to make the 45 degree butt joint.

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    Make the cut and remove the stray pieces of vinyl.

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    Press the edges together.

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    The vinyl needs to be wrapped around the face frame and glued.

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    It is helpful to use blue painter's tape to mark the gluing boundary. The adhesive is applied and then the tape is removed before it dries.

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    Some extra vinyl was left on the face frame. The vinyl is fitted, this piece can be trimmed to ensure that there isn't a gap at the seam, otherwise the wood will show through. This is where staining the wood before the adhesive is applied is useful. This is an example where the vinyl is initially trimmed initially and then the edges trimmed again after the adhesive is applied. In this case, final trimming is only done when the two vinyl pieces are mated at a seam. Push the vinyl down tightly against the vertical frame with a putty knife and cut it on the horizontal frame. That way it won't be cut short. The edge of the bottom frame vinyl will push up against this piece of vinyl.

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    The left side of the bottom frame is fitted.

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    The right side of the frame is fitted.

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    Then the vinyl is wrapped into the cabinet.


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    The joint cuts on the bottom of the cabinet are next.

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    There are 45 degree cuts at the corners.

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    Horizontal and vertical cuts along the edges. How big the edges are and therefore where the joints are is a design decision.

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    Removing the trimmed pieces from underneath.

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    The bottom and lower front face frame are completed.


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    The top face frame and cabinet top rail is next. The vinyl is laid out, marked, and pre-trimmed.

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    The logo goes on this face frame. This is what attracts your eye when you look at the amp.

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    As with the bottom frame, layout is very important. You want the check squares to align with those on the left and right frames. This is most noticeable at the 45 degree joint at the frame corners. You want a line of squares along the top of the face frame, you also want the squares to align with what will be the left and right face frame 45 degree joint.

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    Check that the vinyl is square and that the checks are aligned with the top side pieces. It is more important to have the front face frame aligned than the top. Again, those up down left right micro adjustments come into play.

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    Make the vertical cut against the inside of the face frame.

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    Make the butt joint cut.

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    Wrap the vinyl into the cabinet. Here, rather than using blue painter's tape, a scrap piece of vinyl is being used as a gluing guide.

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    The completed front top and face frame.

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    The vinyl at the corner will need to be trimmed before the metal corner is installed. The corner will cover the vinyl pieces that came together at that point. It's going to look great!

    Cabinet Lid (top)

    The main part of the cabinet is now completed. Following a specific order, the cabinet lid will now be covered. The first thing to do is to test fit the lid. The old vinyl may have been thinner than the new vinyl so test fitting is important at this stage. Place some vinyl around both the front and back edges of the lid and test that the lid will fit into the cabinet. The lid should fit without rubbing with about 1/32", a business card, around the opening. If it is too tight, this is the time to adjust the fit by sanding down the long edges of the lid.

    The cabinet has to be completed first because you want to checks in the vinyl on the lid to align with the cabinet. A diagonal row of checks from the top front of the cabinet should continue across the lid and match up with the checks at the back of the cabinet. This isn't always possible but that's the goal. So the first step is determining the best position. You would like a Full row of checks along the front top edge of the lid.

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    Once the best position is determined, mark the back side of the vinyl as before.

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    Mark where the vinyl should be trimmed. Rolling the wood up helps determine where the side marks should be. It is always best to use the wood as a gauge rather than a ruler to match the exact thickness of the wood to the lines.

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    All the lines are now marked.

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    Glue the top face of the lid first. Stand the lid up against the edge of the glue line and roll it onto the vinyl. This will ensure that the pieces are mated squarely. The same procedure was used with the cabinet.

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    Roll the vinyl with the J roller to ensure good adhesion.

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    Double check the positioning. Note how a full check starts on the top edges. This indicates that you got it right.

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    The alignment looks perfect.

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    Glue the long side and the back of the lid next. Butt joints will be used on the edges so plan on where the glue should be applied.

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    Fold over the vinyl. It's important to roll the edge of the lid. If there are any lumps where too much glue was used, they can be Compressed to some extent with the roller.

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    There is a small overlap of the side flaps. This is where the joint will be.

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    Cut the butt joint along the center of the lid.

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    Press the edges together onto the wood.

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    Now the ends will be done. A 45 degree joint will run from the corner to the center seam. There will be a "Y" at each end.

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    If you look carefully at the end of the lid, it is "D" shaped at the left and right side because of the small round over of the long edges. The vinyl needs to be trimmed but with enough left so that the "D" is covered.

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    The end flap is cut slightly wider so that when it is folded over, the "D" at the end is covered.

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    Glue is applied to the end flap and to the wood. When dry the flap is folded over and the edge is bonded to the wood.

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    A butt joint cut is made from the tip of the lid to the center seam.

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    Another butt joint is cut on the other side of the lower side flap.

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    The flap is pressed down onto the wood.

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    A piece of vinyl at each corner needs to be trimmed.

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    It helps to turn the lid on its edge.

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    Unlike the cabinet, there are no metal corners to cover any rough mating edges. The edge is rolled with the J roller, particular attention is taken to ensure good contact at the end where the D round over is. The vinyl surfaces are pinched together at the end and it rough trimmed.

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    Pinch the vinyl together some more and re-trim with some small sized clippers. This is best done in stages. Some light taps with a metal finishing hammer can add some finesse in seating the vinyl against the edge.

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    Perform the final trim. Often you can see a line from the cloth backing that is on the vinyl. This can be hidden with a felt pen. Now the other end of the lid needs to be done.

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    It looks pretty good.

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    Here is is from another perspective.

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    The lid vinyl application is compete. This is the top side.

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    This is the bottom side. There are four round flat bottomed holes on the bottom of the lid. This is where the plateform vibration mounts are located. Find these holes by pushing with your finger. You can see the indentations where they are located.

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    Make two cuts in an X pattern.

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    Push the flaps in and glue them in place.

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    It's not a problem that the wood is showing. Some cyanoacrylate glue works well here.

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    All four holes have been revealed.

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    The vibration mounts are positioned.

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    They are screwed into place covering the holes.

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    All four are now mounted.

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    There are two other holes the need to be located and the vinyl pierced and glued as was done for the vibration mounts. These metal tabs are where the speaker wire connectors are made. They are attached to the lag bolts that are screwed into the side of the lid. The speaker circuit pathway runs through the tabs, the lag bolts, the latches, then on to the speaker. Details of how this is done are presented here.

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    The completed lid with the hardware mounted. The amplifier tray will be attached to vibration mounts.

    Amplifier Tray (top)

    The amplifier chassis rides on the tray. The tray is mounted to the cabinet lid via the vibration mounts. They tray is covered with a lighter weight black levant material. This is the same weight of material that books are covered in. As such, working with this material is a little easier than with the check vinyl.

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    The tray has been prepared for covering. The old vinyl was removed, the glue removed, the wood sanded, and the surface wiped down with a solvent.

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    The long sides are covered first. Nothing fancy. The vinyl wraps around the sides and over the top.

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    A 45 degree butt joint cut will be made in each corner so leave enough extra vinyl to extend around to the side.

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    Closer detail.

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    Bottom detail. The metal anchors that the chassis screws go into can be seen on each side.

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    The sides are covered by following the same procedure. Because of the thinness of the material, it is best not to overlay the seams and use butt joints.

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    The finished tray mounted on the lid.

    Corners (top)


    The corners of the Portaflex cabinets are knocked off. This allows the metal corners to fit snugly against the cabinet surfaces. Any excess vinyl that would push against the corner can be trimmed away. The corner is put in place. It helps to tap it with a rubber mallet to seat it in place. Check that it fits well. The corner can be adjusted if the nailing tabs are bent. Tap the nails into place. It helps to cover the nail head with a cloth so that the chrome isn't damaged by the hammer. Modern cabinets use screws instead of nails so consider that option. If using screws, it helps to pre-drill smaller sized pilot holes. A drill bit about half the diameter of the screw shaft works well. Here's a tip for making a depth gauge. You don't want to drill through the cabinet. Measure the length of the screw, wrap some masking or painters tape around the drill bit starting after the length of the screw. When you drill down, stop when you reach the tape. Holes can be pre-drilled when using nails as well but this is optional. Pre-drilling helps avoid bent nails and makes it easier to ensure that the fastener goes in square.

    On corners where metal feet are installed, the glide or foot goes in instead of the nail.

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    Trim excess vinyl away at the corner

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    Test fitting the corner

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    Rubber mallet used for seating the corners

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    Depth gauge can be made with tape wrapped around the drill bit

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    Use a cloth to avoid damaging the chrome surface

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    Installed corner

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    Seven more corners to go

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    Glides (top)

    Glides which are also called bottom studs, have split prongs that act like nails. The studs are hammered into the holes in the metal corners in place of the nail or screw and sit on the corner. The same precautions used when hammering in nails should be followed here.

    On some cabinets, they stand alone and sit on the vinyl. It is important to not cut into the vinyl when installing these ones.

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    Bottom stud showing split prong

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    Damping Material Inside the Cabinet (top)

    The vinage cabinets had a spun glass insulating product used for the Damping material. Modern amps use alternate materials such as spun cotton or felt for safety reasons. The rule of damping says to line a ported cabinet and fill a sealed cabinet. Vintage Portaflexes are ported cabinets. The damping was only installed on the rear inner wall of the cabinet. Some people choose to install it on all surfaces. The vintage cabinets used glue to affix the material.

    In this case, the vintage look was desired so a dense insulating/soundproofing material was used. This particular product has a Solid back which makes it easy to cut to size and install. A liquid or spray glue, or double sided carpet tape can be used. The advantage of the tape is that it makes it easier to remove the damping material if it is damaged and needs to be replaced.

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    The damping material.

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    Solvent based contact cement was used in this case.

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    Spread the solvent onto both surfaces.

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    Grille Cloth (top)

    Installing the grille cloth so that it is tight, aligned, and not stretched can be very difficult. On most amps, the cloth needs to be wrapped around a baffle or grille frame, pulled tight and stapled. This can lead to uneven tension and wavy lines in the cloth. As you will see, it's a bit easier with the SB-12. The cloth is simply laid down over the baffle, aligned, and stapled.

    Ampeg used a 1/2" Wide by 1/4" staple. The 1/4" is enough to hold the cloth in place and allows you to easily remove the staple if there's a problem. The staples used are not the type that you use with paper. A heavier staple such as an Arrow T-50 1/4" is necessary. These are available at hardware stores along with a variety of manual, Air, or electric staplers. The powered units make the job easier but a standard spring type staple gun will work just fine.

    The vintage Ampeg SB-12 grille cloth is available at Fliptops or other parts suppliers. It is 36" wide and approximately 24" are needed. Some suppliers sell it by the foot, others by the yard.

    Some like to install a layer of Thin black felt onto the baffle board before the grille cloth is installed. The felt acts as a padding between the baffle and the cloth. It helps prevent a Loose cloth from flapping against the baffle. The felt is about 1/16" Thick and is available at fabric stores. It can be glued onto the baffle and then cut away from the speaker opening and edges. Ampeg used a rubber based foam on their vintage cabinets. Over time, this material broke down to dust. On many cabinets, there's no evidence that it was ever there. They stapled this foam in place and often if the the staples were protruding a bit, would cut the grille cloth. Not a good thing so if you are installing a pad, it is best to glue it in place.

    To install the cloth, lay it down on the baffle and position it so that the lines in the cloth run perfectly horizontal. You want to position the cloth so that the lines are centered about the top and bottom of the wood brace that runs in the middle of the speaker half circle cutouts as best as possible and the lines are horizontal in the opening of the cabinet face. When the position is fixed, tack the cloth in place. Check and double check, then start stapling. The grille cloth is stapled directly onto the face of the baffle board along the outer edges. The staples are hidden by the cabinet's front face when the baffle is installed. The staples should be positioned close to each other so that there is even tension holding down the cloth. When one side is completed, recheck the alignment, then with an even tension on the cloth, staple down the opposite edge. One trick is to place a smaller sized piece of plywood over the cloth and clamp it to the baffle. This locks everything down and allows you to just staple around the edge. I like to do the left side, then the right, then the top, and finish with the bottom.

    When the stapling is completed, if the cloth is bit loose it can be heated with a hair drier and shrunk to fit tighter. Keep the drier moving so that the heat is not concentrated in one spot. Otherwise the grille cloth can melt. Another approach is to heat an oven, Open the door and hold the baffle in front of the opening. Move it in an out to adjust the heat and see how it looks as you go. If the pressure is even on the cloth it will shrink uniformly and the lines in the cloth will remain even. With enough experience, you can place the entire baffle into the oven.

    If all else fails, don't fret, you can do it all again.

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    Arrow spring staple gun that accepts 1/4" T-50 staples.

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    Note the grille cloth lines centered about the top and bottom of the speaker brace.

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    The cloth has been a final trimming around the edges.

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    Rubber Lid Gasket (top)

    The gasket serves to seal the lid against the cabinet and prevents air leaks that could cause a buzzing. The gasket is a closed cell foam rubber. With time the gasket can become hard and looses its ability to compress. When this happens, air leaks can occur and it needs to be replaced. The gasket is available from Fliptops as well as some automotive and hardware stores. In some cases, you will need to trim it down to size to fit. Fliptops makes it easier, you simply buy it by the foot and install it. Some gaskets come with an adhesive on the bottom, simply peel the protective paper off and stick it in place.

    There are two ways to install the rubber gasket, compress fit it in or glue it in place. Either method can be used although gluing it will ensure that it stays put. It can be glued in with a small amount of rubber cement. Don't use too much because, with time, the gasket will need to be replaced.

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    Clean the gasket trough of any residue from the old gasket or glue, or dust.

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    Apply a small amount of glue, you should only spread it on the bottom of the trough. If the glue creeps up the side, it will hinder the compression of the gasket. The less you use, the better.


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    A syringe helps to apply the glue into the gasket trough without getting glue on the side walls.

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    Spread the glue evenly onto the bottom.

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    Insert the gasket along the trough. Apply downward pressure but don't stretch it lengthwise.

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    Don't cut it at the corners, keep it as a single piece. This will help it form a better seal.

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    When you reach the starting point, cut the gasket a bit longer than is necessary. Compress the gasket back a bit to ensure a tight fit with no air leaks at this joint. You can apply a small amount of glue on the end.

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    Comparison of different type of gaskets.

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    Different types of foam will compress differently depending on the material and the density of the foam's matrix.

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    Another example of how the foam compresses.

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    The original gasket.
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