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Rookie build - advice welcomed!

#21
Great advice ct. Makes perfect sense. I wish I had read it 30 minutes ago. I hooked it all up and got dead silence on every combination of settings I tried. I'm guessing - and I mean guessing - something is getting grounded where it is not supposed to be. A bad solder joint somewhere wouldn't kill everything. My design may be flawed in many ways, but I don't see a reason I would get nothing. Ideas welcomed. Nothing more fun than tracing circuits with a meter!
 
#22
MrBohjangles said:
Great advice ct. Makes perfect sense. I wish I had read it 30 minutes ago. I hooked it all up and got dead silence on every combination of settings I tried. I'm guessing - and I mean guessing - something is getting grounded where it is not supposed to be. A bad solder joint somewhere wouldn't kill everything. My design may be flawed in many ways, but I don't see a reason I would get nothing. Ideas welcomed. Nothing more fun than tracing circuits with a meter!
Click to expand...

Ugh. I've had that sinking feeling before too.... :(

My first guess would be one of the controls shorting against the aluminum foil. Remove the pots and switches to make sure they're not touching it and try again?
 
#23
I think you are right on target for the most part. Working backwards, the first thing I checked was for continuity at the jack between ground and signal. It failed - there is short between the two. I was happy to find something right off the bat. Assuming the jack is good, I went to the next step back - volume pot. Once again, short between the ground and signal-out terminals. Odd thing is, no short between the signal-in and ground. Still investigating. By the way, I never noticed all the basses you had in small font in your signature tag. I clicked on a couple. Very cool. Didn't realize I was getting help from a true pro. I'll check the rest out later. Thanks again.
 
#24
What do they say... if it seems to good to be true it probably is. I realized what I was talking about above about continuity has to do with where the sweep on the volume pot is set and not a short. So I kept working backwards. One at a time I would loosen a switch or pot, press it slightly off the foil and try for a signal. Nothing. I was fairly careful putting things together and I don't see an issue that would short everything. So two questions if ct or anyone else knows that could be possible issues...
1. In general I always thought you would want to ground the shell of the pot or switch. When fully installed I have two switches that show continuity between foil ground and shell and 2 that don't. Which way do you think they should all be? I've never done a build like this but I've shielded several basses and always have the shells grounded. Its always worked fine, but I'm running out of ideas so worth a question.
2. Could this problem have something to do with the output signal from a blend pot being used as the input for a volume pot? I'm getting the feeling I have a design problem in this area. The rest of it is just switches and the output.
 
#25
Thanks for the "true pro" comment, but no, I'm just a passionate amateur!! :laugh:

The shells are usually grounded, but technically they don't have to be. It can help with shielding if they are, and most of the big guitar companies ground the shells because they're lazy and just bend the tab back to the shell instead of attaching a legitimate ground wire. :meh:

Output from blend going to input of volume is very common, so that's okay.

You have quite a few components in that circuit. It may be a good idea to take things back to essentials and test one thing at a time:
  • Pickup straight to jack - check for signal
  • Pickup to its coil switch straight to jack - check for signal
  • Pickup to its coil switch, then to blend pot, then to jack - check for signal
  • etc.
 
#26
Thanks ct. Sounds like a project for tomorrow. I'll take the neck and string off and call it a night. Looking at layouts for blend to volume pots on the web, it noticed that most have the two non-used corners of the blend grounded where I have them open. I was just fooling around with alligator clips and wire to see if that was it. Once again, not it. The sun will still rise tomorrow. I haven't done a guitar before, but I have restored stuff way more complicated than this. Its either going to be something stupid or a design flaw (since I made that up and I don't really know what I am doing).
 
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#27
So, following up on the troubleshooting... I think there were a laundry list of potential problems that may have prevented the bass from producing sound. I dis-assembled everything up to the volume pot and started first just looking at my design. The precision pu is pretty straight forward. But I basically had copied the design for all of the hb wiring options from another source without really fully understanding how it translated to my hb's. North and South, starts and finishes, and positives and negatives - learned a lot this weekend just reading. I'm still no expert and I'm not convinced what I did was wrong or it was the root issue, but it will be better understood when I re-assemble. Part of this journey is learning and this is a good example.

At this point I have basically tested all the pu wirings individually on a bench with alligator clips and such - circumventing a blend or volume - and each one has worked. I first re-assembled the precision circuit in the bass, and it worked through the volume/tone/jack in the bass on both series and parallel. When I added in the blend pot - dead as a door nail. So something there to look into. Unfortunately I busted the precision switch by accident and being the wiring that sits at the bottom of the rats nest, we'll have to wait for the new one to arrive to proceed.

Got a question for CT or anyone else... should I have any concerns with mixing pickups? I know you can run into phase issues with single coils, but I couldn't find a straight answer given all of mine are hb's of one variety or another. The bridge and neck hb's are the same, so no issue there. What about blending in the p? Anything to be on the lookout for? Thanks all.
 
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#28
Kudos for taking the time to research, study, and develop and understanding of the underlying principles at work! :thumbsup: I'm a big believer in the "teach a man to fish" principle.

Concerning combining pickups, there are (at least) two things to consider:
  • Phase. You've already mentioned that. Phase problems are usually obvious (thin, reedy sound) and usually easily remedied (flip the hot and ground leads). The only real problems here are pickups that have their signal ground and shield ground permanently attached to the same lead; if you flip hot and ground you still want the shield to remain attached to ground.
  • Impedance. When passively mixing two different pickups of different resistances, the resultant circuit can result in one pickup "swamping" the other one. An extreme example is the 30k Gibson mudbucker combined with the 8k Gibson bridge mini-humbucker. The issue here is that (when passively mixed, with a blend or switch or two volumes) each pickup "sees" the load of the other one, and they don't always interact well. I don't fully understand the "why" behind it, but others do, and will surely be along to comment. An active (buffered) blend addresses this, at the expense of requiring a battery.
 
#30
You guys will like this rookie error. Was fooling around with some tests today and getting very strange results with the volume pot - like no sound. Thought I was loosing it. Did a little digging and realized I had bought a no-load pot. Until today I had no idea what the difference was. Turns out this is a bad choice for volume :). Could swear it worked at least some of the time when I was testing, but maybe not. Live and learn. More parts to be ordered.
 
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#31
So I carefully built the pu circuits and tested every step along the way using ct's suggestion of a piece of metal to tap the pu's (no neck or strings). Tested what I thought would be the correct wiring on the bench before starting. First in was the p-pu and switch directly to the jack. All good. Then bridge hb and switch directly to jack. All good. And so on as it got more complex. I am quite confident that all the pu's and toggles are working correctly at this point. They may sound awful later, but they are making noise as they are supposed to. I added in a 500K blend pot. Everything still working, although I think I still hear faint p-pu when its fully on hb. We'll see about that when it gets fully set up. I bought new volume pots (I've been buying both a 250K and 500K each time in case I want to swap later) to correct my no-load issue in the last post. My first guess was to start with the 250K, but I bought the wrong thing again. I know better, but I bought one with a shorter thread length and it doesn't fit. Doh! The 500K I bought is the right one. I'll probably give it a shot. Replacing the volume pot would be the easiest thing to do in this whole project. Do you guys have any opinions on pot values in my case (MM hb's with a p-pu). I also have a 250K blend pot I could swap with the 500K if needed.
 
#32
Step 6: Test Drive
Put it back together, set the neck and string lengths. Only alterations from the original layout are a 500K volume pot (vs. original 250K) and I chose not to install the OMG caps on the hb serial modes (but left the option to add them later). Results are interesting. Wide variety (very wide actually) of tones can come out of this one instrument. Its obviously not finished. I need to cover the cavity to spruce it up. But I also need to look more into how pickup heights, phase issues, and blend/vol pot values are affecting its sound.

On a side note, first time I've gotten to hear the hb pickups. Not trying to pimp them or anything, but I bought them on Amazon for $13 each (remember the original goal was a decent instrument at a minimal cost). They exceed my expectations for sure. Wouldn't hesitate to buy them again - although I think the price has gone up. If interested, the p is an Artec Alnico5 set. They will do, but don't wow me.

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#33
After a little test driving, a few observations and a rookie mistake found. Took some measurements that explain exactly how the bass behaves in different combinations:

Neck HB: Series = 12.4KOhm, Single Coil = 6.2KOhm, Parallel = 3.1KOhm, Phase = Neg (my term)
Precision: Series = 8.9KOhm, Parallel = 2.25kOhm, Phase = Neg
Bridge HB: Series = 12.5KOhm, Single Coil = 6.25KOhm, Parallel = 3.13KOhm, Phase = Pos

Remember: I have a switch that allows me to isolate either HB or combine HB signals that then feeds into a blend pot along with the p signal

First thing I observed is the blend pot doesn't do a lot of blending. Its more of a 3-way switch. At center detent its combining 100% of each signal, and there's a little blend just to either side of the detent and then the primary signal overwhelms the other. Oh well, not quite what I was hoping but not the end of the world. Still plenty of different sounds to be had (141 theoretical combinations if my math is correct).

The other thing I noticed was something was not quite right with any combination of the bridge HB. Neck HB and P pu gives a punch in the gut bass, particularly on series/series. Bridge HB and P pu gives you a really thin, distant sound particularly in parallel/parallel. So I knew something was wrong. I figured its a phase problem and the tests above confirmed. Turns out I didn't even follow my own wiring diagram correctly. I swapped which of the two start leads I grounded instead of swapping their positions on the switch. More soldering coming up - I was really hoping not to take it apart AGAIN! Or maybe I'll leave it and keep the potential of all the odd out of phase tone possibilities - of which there are many :)
 
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#35
So I fixed the wiring mistake and everyone is playing nice with each other now. While I was in there I installed the OMG cap on the HB's serial mode. I'm not sure OMG would be my description of the change. To me its a subtle difference at best, but it's all good.

So only thing left is to craft a pickguard. The opening is about 4x4, so I was looking for somethings at least 5x5. Didn't want to spend $20 on pickguard blank material. Ended up ordering laminate countertop samples from Home Depot. They come in 5x7 ($0.25 each) and 8x10 ($1 each). They are about 1/2 the thickness of a standard pickguard. So I picked 6 interesting ones out for a total cost of $4. I'll choose the one I like best and bond it to the one I like least and cut it to form. Worst case I'm out $4 and move to plan B. All part of the journey.
 
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#37
Step 7: The Finish Line
So its been over a month since my last update. Was a combo of COVID shipping delays and trying to figure out exactly how I was going to make a custom pick guard. Some of the videos I had watched warned me it can be a pain in the a$$, and they were right. I admittedly did a poor job of documenting what I did in this step because it was a lot of trial and error.

The overall process was using multiple layers of cereal box cardboard to get an outline. I transferred that to a piece of 1/8" plywood and cut it out. Then used that as a template to rout the final product from laminate countertop samples. But this is way oversimplifying all the little tweaks and trims required at each step to be half way decent. It was a royal pain.

If anyone is reading and following along, I would not recommend using laminate for your pick guard. It's almost too thin to work with if that makes sense, and its not really moisture proof. I hadn't considered this when choosing to go this way. It works for this project, but I wouldn't do it again.

This is the only pic I took during the design phase. Yes, it was as much of a cluster as it looks like, but it was the best of many attempts I tried.

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Anyway, this is the finished product. This wasn't my first choice of laminate design, it was actually my practice piece. But it was such a pain to do, I said that I will learn to love it (actually it's fine). Thanks for reading along and a big thanks once again to those who provided help and encouragement along the way. It was my first real hot rod project and it was both fun and enlightening... along with aggravating and time consuming. But its all good. Stay well and enjoy your summer!

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#38
Glad it worked out. Should you try to do that again, you might make the pickguard out of thin plywood. I think Home Depot has 1/8” Birch plywood, if not it can be ordered online. Once the guard is cut out, fill and finish the edges of the plywood as needed then glue the laminate to the ply. Another option that might work better with a bevel on the side of the guard but is a little more complicated would be to glue the laminate on first then cut and shape the ply then fill and finish the edges. You’d have to tape off the laminate during the fill and finish part but, usually, a bevel looks nice on a pickguard.
 
#39
Matt, I should have mentioned that part of my challenge was not having better tools to work with. I did this last step with a hand jigsaw, a plunge router, scissors and files and sandpaper. A scroll saw and a router table would have made a big difference. If I was going to do this repeatedly, I would make sure I had those on hand. I considered an option similar to what you mentioned. I ended up damaging the thin ply template when routing the laminate, so just went with the laminate with a copper tape backing for a little support and shielding.
 
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