Tragedy strikes my Jack Casady... Any thoughts?

[Big Fat Walrus]

My next idea would be to freeze the component then put the metal in hot water and see if the thermal shock would loosen the epoxy from the cover. Maybe that would allow me to check out the embedded part.

My god, why do you keep going to this idea? Step away from your shock theory. Epoxy is an adhesive, and it gets softer with heat. You do realize that a transformer of this size is just a bunch of very small copper wires wound around some poles, yes? Why would you want to subject such an otherwise working, hard to commercially obtain and highly conductive material to such an extreme situation? You don't have a faulty transformer, you have a faulty wire. Why are you trying to bring collateral damage into this?

I have extricated far, far more expensive (and truly unobtainium) PCBs from inches of potting with the steps I laid out above. If you don't have the patience for the battle ahead, then don't even begin. I have no stake in this outcome other than wishing a fellow musician a DIY victory, but it seems like you are not truly thinking your approach through here.

Again, best wishes for a positive outcome

 

[Wasnex]

View attachment 3874666 Apparently the electronics design is based on the Les Paul recording bass and the wiring is compared in this photo. Perhaps a new thread with a direct electronics question might attract the attention of one of our electronics gurus right here on TB? I've gotten some great help here and imagine our members could reinvent the entire wiring harness.

Nobody seems to have noticed that the P/N for the transformer is included in the attached document (70-043). With this number you have a much better chance of eventually getting the correct part. Pretty sure this is a proprietary part that you will not find at Mouser or Digikey. It will probably need to be sourced from Gibson supply channels.

I had similar problems getting a replacement tone control knob for my Yamaha TRB6P, so this sort of problem is not unique to Gibson and Epiphone. Dealers could not help me, and I tried dealers in both Germany and the USA.

I don't remember exactly how I got the knob, but I think it was something like this: I made a contact at MusikMesse in Germany who was pretty high in the US Yamaha musical instrument distribution heirarchy. He told me to try and work things up their distribution chain when I got back to the states, and to give him a call if I didn't get satisfaction.

I did exactly what he said. I started with dealers. They tried to help but were getting nowhere so I asked for the name of their distributor and worked my way up the distribution network. Eventually I pulled the card out and called "Mr Big" and told him the names of all of the dealers and distributors I had spoken too who said they could not help me get a simple control knob. It was lucky that I called him when I did, because he was moving to a new job. It took a few more follow up calls but I eventually got the knob.

The point is, make phone calls, take notes, and continue to go up their chain of command until you get satisfaction. If they say they will only work with a dealer or authorized repair center, then provide the names of places who say they can't help you, and then ask them to point you in the direction of someone who will actually help resolve the problem. If that person says they can't help, continue to make it an issue higher in the distribution network. If possible try to work with the same person in the distribution network until they get tired of dealing with you and pass you to someone higher in their chain of command.

 

[Verner]

My god, why do you keep going to this idea? Step away from your shock theory. Epoxy is an adhesive, and it gets softer with heat. You do realize that a transformer of this size is just a bunch of very small copper wires wound around some poles, yes? Why would you want to subject such an otherwise working, hard to commercially obtain and highly conductive material to such an extreme situation? You don't have a faulty transformer, you have a faulty wire. Why are you trying to bring collateral damage into this?

I have extricated far, far more expensive (and truly unobtainium) PCBs from inches of potting with the steps I laid out above. If you don't have the patience for the battle ahead, then don't even begin. I have no stake in this outcome other than wishing a fellow musician a DIY victory, but it seems like you are not truly thinking your approach through here.

Again, best wishes for a positive outcome

I am just curious about what the actual component is under the hood, I want to know that almost as much as I want my bass to work! I understand it is frustrating to watch an inexperienced person attempting to do a repair you have experience with, totally get it, I give music lessons on zoom. Explaining how to tune a violin online is an exercise in patience.

I am confident that this bass will work again, one way or another. I have dug down quite a ways though and haven't found a lead. So if the epoxy brick can slide out it may give me some info I can't get otherwise. Didn't say it was a good idea, just an idea.

 

[Verner]

Nobody seems to have noticed that the P/N for the transformer is included in the attached document (70-043). With this number you have a much better chance of eventually getting the correct part. Pretty sure this is a proprietary part that you will not find at Mouser or Digikey. It will probably need to be sourced from Gibson supply channels.

I had similar problems getting a replacement tone control knob for my Yamaha TRB6P, so this sort of problem is not unique to Gibson and Epiphone. Dealers could not help me, and I tried dealers in both Germany and the USA.

I don't remember exactly how I got the knob, but I think it was something like this: I made a contact at MusikMesse in Germany who was pretty high in the US Yamaha musical instrument distribution heirarchy. He told me to try and work things up their distribution chain when I got back to the states, and to give him a call if I didn't get satisfaction.

I did exactly what he said. I started with dealers. They tried to help but were getting nowhere so I asked for the name of their distributor and worked my way up the distribution network. Eventually I pulled the card out and called "Mr Big" and told him the names of all of the dealers and distributors I had spoken too who said they could not help me get a simple control knob. It was lucky that I called him when I did, because he was moving to a new job. It took a few more follow up calls but I eventually got the knob.

The point is, make phone calls, take notes, and continue to go up their chain of command until you get satisfaction. If they say they will only work with a dealer or authorized repair center, then provide the names of places who say they can't help you, and then ask them to point you in the direction of someone who will actually help resolve the problem. If that person says they can't help, continue to make it an issue higher in the distribution network. If possible try to work with the same person in the distribution network until they get tired of dealing with you and pass you to someone higher in their chain of command.

Yes, I like this

 

[Verner]

Do you have a Multimeter? If so do you know how to measure continuity? This is a long shot but follow schematic below:

View attachment 3874986

So this kind of works, I can get a signal out to my amp but it is very weak. If I prop my phone close to the pickup it will play the music through my amp. I am not good at reading schematics, but it seems like the signal chain must go from pickup to controls and then to the transformer to boost everything. So I am wondering if this wiring is just the weak signal coming from the pickup, pre-transformer?

 

[Big Fat Walrus]

So if the epoxy brick can slide out it may give me some info I can't get otherwise. Didn't say it was a good idea, just an idea.

It is not going to 'slide' out, so I'll spare you the suspense. It will come out in teeny weeny little chunks that will be all over the floor of your apartment (hobby room in house?) for years to come. Once you have broken away enough of that bonding material you will be able to wiggle the transformer out of the casing. It won't take much effort at that point.

As to the P/N# attachment, well... That isn't an actual print (vs. what subhuman posted, which is). That is some random internet user's (cadfael?) PNG graphic which could be wrong or could be right. Who knows. But as someone who currently works in manufacturing, I wouldn't trust that graphic over any actual print (read the notes in subhumans print re: permission and litigation. It is a blessing someone risked their job so that we could all see it). There is nothing noted in the actual print about any part number. 70-043 could refer to a lot of things, but it seems to be a non-proprietary part as indicated by the actual manufacturer's print.

And that is a nice story about a tone control knob, but did Yamaha really have a 22/64.7894 K reverse B taper potentiometer custom manufactured for that specific bass? No, they didn't (obviously). So it was already commercially available (which is why they used that value). So who is to say whether Yamaha just simply got annoyed enough to respond to a question 'Mr. Big' should have never been answering (especially as one of the last things he did on the way to his new job) or not. But the fact remains: if all of these things weren't readily available from some supplier, they most likely wouldn't be inside your instrument unless it cost more than, say, 8 or more K...

 

[Big Fat Walrus]

So this kind of works, I can get a signal out to my amp but it is very weak. If I prop my phone close to the pickup it will play the music through my amp. ]

That is not how continuity works, my friend. It is never weak nor strong. Does your meter have a symbol on the dial that looks like this: .))) - (but imagine the period was in the center of the parenthesis)? If so, and it doesn't beep when you touch your probes to the terminals, you do not have continuity between points. Game Over.

 

[Verner]

That is not how continuity works, my friend. It is never weak nor strong. Does your meter have a symbol on the dial that looks like this: .))) - (but imagine the period was in the center of the parenthesis)? If so, and it doesn't beep when you touch your probes to the terminals, you do not have continuity between points. Game Over.

Oh, I didn't test with the meter yet, I just touched the output wires to the points indicated to see if I got a signal coming through my amp or not. I will have more time to sit with it after the kids go to bed.

 

[SubHuman]

What you really need to soften the epoxy is a commercial heat gun or butane soldering iron and focus the heat right on the area to soften and remove the epoxy and expose that pin. If you don't know what you're doing you can melt plastic and wiring pretty quickly. Maybe even cause a small (toxic) fire!
Sounds like Walrus has done this before and so have I so I wouldn't hesitate to literally "dig right in" and free that pin. I have done similar repairs to PCB's so not anything new to me.
It's a shame manufacturers don't have better customer support. I guess that's the price we pay for having China make everything. No components available in the good old USA. Anyway hopefully that ground wire was attached to the other part of the circuit before the potting was poured over the wires. The continuity test will confirm that is true if they wired it that way. Fingers crossed!
If so it's an easy fix. Good luck!

 

[Big Fat Walrus]

Thank you, sir-

As an American machinist I cannot stress enough how much QC is given up once things are made for profit over quality... We already knew those components are not proprietary or unique. Which is why you (Verner) should not hesitate to 'dig right in' and find out the values of those components (being careful and cautious, of course. Especially since it sounds like this is your first 'excavation' job site). You might save many others from the same horrible fate of indifferent Customer 'Service.'

For full disclosure - I own a 2004 Epiphone LP Standard bass. I love it, I have changed out tuners, bridge, jack plate, nut. Straplocks. Think that about does it.

But also, thanks Sub for your schematic. Doesn't matter to me currently, and don't know how you got it, but thanks. I also build a lot of pedals (nothing in my fleet isn't built by me), so it might be more useful than i had thought. Maybe I'll stick a similar circuit in a box someday. And if I ever get a JC (not likely, as I GAS much more for a Midtown), I'll be prepared for the challenges at hand

 

[Big Fat Walrus]

So this kind of works, I can get a signal out to my amp but it is very weak. If I prop my phone close to the pickup it will play the music through my amp. I am not good at reading schematics, but it seems like the signal chain must go from pickup to controls and then to the transformer to boost everything. So I am wondering if this wiring is just the weak signal coming from the pickup, pre-transformer?

Now I am confused - so you didn't follow his directions at all? They have nothing to do with a phone

 

[Verner]

Two part directions, if that then this. Didn't have meter handy to do that, so went straight to this. Pickup can pickup strings and speakers, so I ran my phone speaker in front of my pickup. Music came out of my amp, but very quietly. Had my daughter hold it over a bass to pickup up the strings, and again came through but very quietly.

 

[Big Fat Walrus]

FYI- that has nothing to do with continuity. Sub was asking you about continuity

 

[Big Fat Walrus]

How to Check Continuity for Beginners

 

[Verner]

If there was continuity, he suggested a wiring. Like I said I just tried the wiring in between dinner and corralling the 2 year old.

 

[Wasnex]

And that is a nice story about a tone control knob, but did Yamaha really have a 22/64.7894 K reverse B taper potentiometer custom manufactured for that specific bass? No, they didn't (obviously). So it was already commercially available (which is why they used that value). So who is to say whether Yamaha just simply got annoyed enough to respond to a question 'Mr. Big' should have never been answering (especially as one of the last things he did on the way to his new job) or not. But the fact remains: if all of these things weren't readily available from some supplier, they most likely wouldn't be inside your instrument unless it cost more than, say, 8 or more K...

Stop twisting stuff and making up alternate stories. I needed an exact replacement knob not a pot. If I needed to replace the pot it would have been much easier to deal with. Any competent technician, including myself could have handled replacing a pot. I did a lot of research at different sites and could not find the knob anywhere. I have never seen the knobs on any other brand besides Yamaha. Yes I could have accepted another knob that fit the pot, but I wanted a matching set on my bass.

I am absolutely certain Mr Big is the one that finally pulled the levers necessary to get me the knob, because after I followed up a few times, he is the one who took my address. I totally agree that Mr Big should not have had to deal with it, and he was a bit dismayed, but at least the buck finally stopped being passed around and someone took care of it. Especially frustrating since the bass was still in production at the time.

Your are correct that the transformer may not be proprietary. However the P/N may be a Gibson P/N that is not relevant outside of Gibson channels. IMHO, the P/N is the best clue we have.

 

[Verner]

I understand how to check continuity, my first jazzmaster build was 50% woodworking and 50% chasing continuity in the circuit. Tons of fun.

 

[Wasnex]

What you really need to soften the epoxy is a commercial heat gun or butane soldering iron and focus the heat right on the area to soften and remove the epoxy and expose that pin. If you don't know what you're doing you can melt plastic and wiring pretty quickly. Maybe even cause a small (toxic) fire!
Sounds like Walrus has done this before and so have I so I wouldn't hesitate to literally "dig right in" and free that pin. I have done similar repairs to PCB's so not anything new to me.
It's a shame manufacturers don't have better customer support. I guess that's the price we pay for having China make everything. No components available in the good old USA. Anyway hopefully that ground wire was attached to the other part of the circuit before the potting was poured over the wires. The continuity test will confirm that is true if they wired it that way. Fingers crossed!
If so it's an easy fix. Good luck!

The heat necessary to remove the epoxy is likely to damage the transformer IMHO.

 

[Verner]

I do want to thank everyone who contributed some great insights and ideas. I am going to continue to try and source the part because I feel like it is something a good company should do. I will be sending out the part to Curtis Novak because he has a much better chance than I do of fixing the part or creating a new one. I really do appreciate the expertise of those who have done this type of work before, but I am not confident I can pull it off without destroying the part. However, there is a lot here that other people will be able to use in a similar situation. If I do source another part or have a new one fabricated, I will free up the guts and let everyone know what is inside.

 

[Wasnex]

We already knew those components are not proprietary or unique. Which is why you (Verner) should not hesitate to 'dig right in' and find out the values of those components

Digging out the transformer may allow repair of the transformer lead. It may also just result in a mess and frustration...but it's what I would do as all the other proposed methods seem likely to ensure the transformer is FUBAR.

Diggin out the transformer is unlikely to give any info on the characteristics of the transformer. The output impedance is dependent on the turns ratios of the transformer windings and the impedance of the pickup. It's not something you can measure with an ohmmeter. Someone with advanced knowledge and test equipment could determine the turns ratio by inserting signals at the primary and measuring the output at the secondary, and then performing the necessary calculations, but that is way over the OPs head IMHO.

Removing the transformer from the casing may reveal a P/N. Perhaps this is where the 70-043 came from. Getting the right part from Gibson is the mostly likely solution IMHO. Of course if you or someone else has a P/N for a generic transformer that has the proper characteristics, that would be awesome and would probably be far easier than dealing with Gibson's bureaucracy.