HOLY MOLY!!! That's awesome, Beans! Thank you!
How would I go about printing a new board? This one is all hacked-up.
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1969 Ampeg SVT Restoration Thread
- Thread starter Chris 'Wighat' Jordan
- Start date
HOLY MOLY!!! That's awesome, Beans! Thank you!
How would I go about printing a new board? This one is all hacked-up.
Yeah look like it has been repaired like the one trace burned up and lifted. Some of the other stuff is probably from being converted to 6550's. Too bad they installed that power cable plug, cut up the chassis on that rare one!
That came from the attached 77 service manual.
A new board would be great. I'm not aware of any replacement boards for the vintage SVT on the market. There is a reproduction one for the main board for the V4 family available on ebay: Ampeg V2 V4 VT22 V4B Main Printed Circuit Board Replacement | eBay.
I don't know if they would be willing to do a board for you. A new board would have to be designed and it would be costly to produce in single numbers. On the plus side, it's a relatively simple, single sided board. A thicker FR4 board would be nice, as would plated through holes, perhaps double up some of the traces, top and bottom layers, that tend to get damaged when plate and screen resistors blow.
It helps when installing these resistors to offset them from the board by a mm or so. If cement block resistors are used, turn them so that the bottom where the glue is, is not facing the board. Flames often erupt from the bottom when they blow. Pointing them away from the circuit board and offsetting their mount helps reduce the chances of damage. When replacing these parts, don't exceed the wattage specified on the schematic. They blow like a fuse when there is a problem. This is a good thing as it can protect the output tubes and transformer. Upping the wattage will prevent the resistors from blowing. I like to buy extra and match the plate, screen, and cathode resistors when replacing them.
How to deal with damaged traces. If they are lifted, they can be glued down. I use a high temperature marine epoxy from J-B Weld. Some people use cyanoacrylate (crazy glue). Never tried it to repair boards. If traces or pads are missing, bus wire can be soldered onto a good trace and run to where you need it. Not pretty, but it works.
Be careful when soldering. Too much heat can lift the traces. So can strong solvents that are used for cleaning.
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I am going to put a repro back plate on it. It will be painted black with labeling etc just like the later SVT's but completely reversible as it's just a sheet that covers the back of the chassis. It will cover-up some of that nastiness.
What about that metal paint used to repair traces?
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If I don't watch-out, I'll find myself sourcing NOS resistors, etc.
Really though, this amp is not a candidate for all-out perfect restoration. It's got a non-stock OT among other things. I'm not going to make it any worse, but the mad scientist in me wants to use these plate caps. They may help with heat dissipation but the down-side is they are not insulated.
The regular ceramic ones are cool too and prolly safer.
Really though, this amp is not a candidate for all-out perfect restoration. It's got a non-stock OT among other things. I'm not going to make it any worse, but the mad scientist in me wants to use these plate caps. They may help with heat dissipation but the down-side is they are not insulated.
The regular ceramic ones are cool too and prolly safer.
I've seen them used on fabric with wearable electronics. Never tried the paint on trace repair products. You need to have enough copper to handle the current.
If the trace is wide enough, you can precut a patch from a sheet of copper and glue that to the board. There are alternatives, sometimes you need to get inventive.
I repaired an amp once that a previous "tech" used solder wick to repair a blown out trace!
Oh, man.
There's a lot of damage caused by well meaning folks. I love it when I take on a restoration and find that the amp is all original.
Got the power, output and heater transformers out. One of the bolts in the OT is broken. Is it cool to remove one bolt at a time completely from a transformer? I need to replace the one but I'd like to pull them out so I can paint the power transformer caps fresh black. Don't want to disturb the plates though.
All that's left on the chassis is jacks, switches, tube sockets, etc.
Removing and replacing all. Gonna get nice ceramic tube sockets for this baby.
All that's left on the chassis is jacks, switches, tube sockets, etc.
Removing and replacing all. Gonna get nice ceramic tube sockets for this baby.
Be careful, not all the current ceramics are good. The metal terminals don't pinch the tube pins well. There are some nice teflon ones at partsconnexion and original replacements are available if you are interested. When you reinstall the sockets, I like to twist the power tube heater wires to minimize the noise. They typically aren't on these amps. Follow these guidelines at the bottom of the page: The Valve Wizard
Yes you can remove the end caps on the transformers. Be very careful. There are insulating washers on some transformers that need to be there. Paint works but if you can find a local powder coater, the finish is superior.
Meaning if I remove all four studs, just handle the transformer gently and put it in a safe stationary place until I get the bolts back in? Thank you for all your help, Mr. Toast. You're the greatest resource I have.
What should I look for in ceramic sockets?
Just got the chassis completely stripped:
Yes. The plates are usually stuck together well. Just treat it with kid gloves. Note how tight the bolts are, you want them retightened evenly and with about the same tightness. As I said, you don't want the bolts shorting the plates.
Some modern sockets do not make a tight contact with the tube pins. New sockets need to be retensioned. Jule had some interesting comments in this thread: #252. A socket with a clamshell contact is good. I like these [Invalid or Expired Link Removed] You would have to ask them about mounting rings and their dimensions. Since you have holes in the chassis, you want to reuse them. That can be a problem. Using the same socket would make that easier: NOS- A8F4 - 8 Pin - Sockets, Adapters and Parts
How are you planning to clean the chassis? Are going to leave it bare metal? Being on the water, do things tend to rust easily where you live?
Some modern sockets do not make a tight contact with the tube pins. New sockets need to be retensioned. Jule had some interesting comments in this thread: #252. A socket with a clamshell contact is good. I like these [Invalid or Expired Link Removed] You would have to ask them about mounting rings and their dimensions. Since you have holes in the chassis, you want to reuse them. That can be a problem. Using the same socket would make that easier: NOS- A8F4 - 8 Pin - Sockets, Adapters and Parts
How are you planning to clean the chassis? Are going to leave it bare metal? Being on the water, do things tend to rust easily where you live?
Yes, we are in a highly corrosive enviroment. Im not sure about cleaning the chassis. I was thinking of having the chassis powder coated. There may even be clear powder coating.
That's what I was thinking. I sometimes use a ceramic coating on bare metal. Just clean the metal well, remove the rust, then coat. The ceramic that I use goes on clear like water and the coating is thin. This was a wipe on product that requires a couple of coats. It does an excellent job though. This is what I use: STEWART SYSTEMS: EVERSHIELD CERAMIC SURFACE TREATMENT from Aircraft Spruce.
A powder coater usually does sand blasting. My guy also does ceramic coatings. So maybe you can get a clear coat. There are a couple of ground points on the chassis where jacks are. The coating would have to be removed at those locations so that the jacks could make contact. Not a big deal.
You can get clear powder coating. Some interesting information on powder coat here: [Invalid or Expired Link Removed]
No question that they can do some amazing stuff with powder or ceramic. I stopped painting as a result.
I've also had some SVT grey front panels powder coated. So if you get the chassis done, that panel can be done as well.
I've also had some SVT grey front panels powder coated. So if you get the chassis done, that panel can be done as well.
I'm interested in this for sure but a little concerned that the heat involved with powder coating could damage the face plate graphics
You can slide the graphic portion out and just powder coat the rest of that front Assy.
As Tim said. You have to remove the jacks, pull the pots back, remove the lamp and two switches. With everything out of the way, the face panel slides out.
If you google "RAL color chart powder coat" or "RAL powder coatings" you can see what is available in terms of color. Coatings are rated for different applications. You want indoor/outdoor weather resistant. I request Slate Grey 7015. It isn't a match for what was used originally but I like it, I prefer a darker grey. If you bring in the original panel they should be able to match it. If they have to order a custom color, it could cost more because they have to buy a large container. I find that they often have something close that will work. The ones in the pic below may have been a darker color.
This is a stripped panel. The high ridges are sanded (scraping can chip the edges) to reveal the metal. I get the painter to run his finger over the coated edges after they are sprayed with the powder. This leaves very little to remove once it had hardened. I find that often these panels need some sanding on the ridges. They often have dings that can be sanded out with a block and made to look better. Specify that you want the inside edges of the cutouts painted, they spray the back in those areas to ensure coverage.
One note about powder coaters. Prices can vary quite a bit so it pays to shop around.
The black panel below is the original one from a V4B. I wound up replacing it with one from fliptops.
The ridges in the image above are before sanding. If you look closely you can see some paint misting over some of the areas.
If you google "RAL color chart powder coat" or "RAL powder coatings" you can see what is available in terms of color. Coatings are rated for different applications. You want indoor/outdoor weather resistant. I request Slate Grey 7015. It isn't a match for what was used originally but I like it, I prefer a darker grey. If you bring in the original panel they should be able to match it. If they have to order a custom color, it could cost more because they have to buy a large container. I find that they often have something close that will work. The ones in the pic below may have been a darker color.
This is a stripped panel. The high ridges are sanded (scraping can chip the edges) to reveal the metal. I get the painter to run his finger over the coated edges after they are sprayed with the powder. This leaves very little to remove once it had hardened. I find that often these panels need some sanding on the ridges. They often have dings that can be sanded out with a block and made to look better. Specify that you want the inside edges of the cutouts painted, they spray the back in those areas to ensure coverage.
One note about powder coaters. Prices can vary quite a bit so it pays to shop around.
The black panel below is the original one from a V4B. I wound up replacing it with one from fliptops.
The ridges in the image above are before sanding. If you look closely you can see some paint misting over some of the areas.
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