New reverb tank needed?

[Jot]

Brought my 1970 Gibson LP1/LP2 preamp head and powered cabinet to an audio repair shop in Baltimore a month ago. I told them that I thought the electrolytic caps might need replacing (single notes sound OK, chords sound distorted, which I believe can be a consequence of old/leaky caps) and that the reverb isn't working right.

Got a phone message from a tech at the shop today; he said that the caps check out fine (I was surprised that he said that) but that the preamp head needs a new reverb tank. The interesting thing about that diagnosis is that the signal from the guitar isn't making it to the reverb tank but the reverb makes a satisfying sproingy sound at a good volume through the speakers when I smack the top of the preamp head with my fist.

So, looking for a second opinion: given that the reverb tank signal makes it from the tank to the output stages, does it still make sense that the head needs a new reverb tank?

[52 Bill]

So, looking for a second opinion: given that the reverb tank signal makes it from the tank to the output stages, does it still make sense that the head needs a new reverb tank?

Yes.

There are two parts to a reverb tank input and output. They are separated by the mechanical springs that create the sprong.

If the amp makes noise when you hit the tank, the output of the tank is working. This does not mean that there can't be problem with the input of the tank. It could be a bad coil or a broken wire to the RCA jack. I assume that the tech has checked the wires to the jack and wants to replace the tank due to an open input coil.

[Jot]

Yes.

There are two parts to a reverb tank input and output. They are separated by the mechanical springs that create the sprong.

If the amp makes noise when you hit the tank, the output of the tank is working. This does not mean that there can't be problem with the input of the tank. It could be a bad coil or a broken wire to the RCA jack. I assume that the tech has checked the wires to the jack and wants to replace the tank due to an open input coil.

Thanks, Bill. That's reassuring. I hope he's right about the caps, since he already quoted $375 for replacing the tank, installing two 3-conductor power cables, replacing a bunch of lamps, cleaning, etc.

[Randall]

That's an outrageous price for that amount of work.

[Jot]

That's an outrageous price for that amount of work.

Thanks, Randall. I was thinking that, too. I'll ask for an itemized estimate. I might even eat the $90 bench fee and take the amp to the longest-established music store repair shop in the Baltimore area, which I should have done in the first place. The shop that gave me that estimate has been there for only a couple of years.

This reminds me, fairly or unfairly, of the pricing of custom-made bicycle frames. There are people who have built two frames in total and then do a fancy website with a list of prices that are sometimes higher than the prices charged by builders who have been in the business for over 20 years and have built many hundreds of frames. And the guys who have been building for decades say that they're still perfecting their technique with every frame they build.

[Randall]

I couldn't look a person in the eye with a $90 bench fee, either. He must be gouging you on the parts prices. Why don't you eat that charge and call it lesson learned, buy a couple new power cords, and a reverb tank and install them yourself and ask your questions here? None of that is difficult. I'm sure you could probably get everything you need from Mojotone or Antique Electronic Supply for under $75 shipped.

[olddawg]

That is a rather outrageous bench fee. I would also give very good odds that they didn't even trouble shoot the unit and gave you a large estimate to send you away or farm it out to another shop. Standard procedure for incompetents. Hopefully you paid or will pay the estimate fee on a credit card. If you did, contest the charge with a simple call to your credit card company. I had a Chevy dealer do $1200 worth of work on my car a few years back. They didn't fix the problem. I had it diagnosed by another shop and their charge was reversed. Always pay with a credit card in these situations.

[Jot]

I couldn't look a person in the eye with a $90 bench fee, either. He must be gouging you on the parts prices. Why don't you eat that charge and call it lesson learned, buy a couple new power cords, and a reverb tank and install them yourself and ask your questions here? None of that is difficult. I'm sure you could probably get everything you need from Mojotone or Antique Electronic Supply for under $75 shipped.

That's great advice; thanks again, Randall. The ironic thing is that the main reason I took it to the shop was that there's fuzzy distortion, particularly in the low notes, when playing chords that might have something to do with the power amp filter capacitors, from what I've read on here. Or it might be something else, or course, but I know enough about the (non-electronics) things I do know about to know that I don't know enough to troubleshoot this amp. I included that fuzzy-distortion symptom when I gave the tech my list of concerns about the amp, but in his phone message he said that he thought the power amp is fine.

Just listened to his phone message again---he said that the power amp seems to check out OK and that the electrolytic caps seem OK and that they could change them, but it would affect the value of the amp (I guess he meant because it's 30-odd years old, somewhat rare, and all original), as well as add quite a bit to the repair bill.

So the $375 estimate is all for doing work on the preamp---replacing the reverb tank, replacing a bunch of lamps (around 13 in total, including lamps illuminating the plexiglas preamp face panel and lamps used for the tremolo, vibrato, and "vibrola" modulation circuits), and cleaning and "tweaking."

[Jot]

That is a rather outrageous bench fee. I would also give very good odds that they didn't even trouble shoot the unit and gave you a large estimate to send you away or farm it out to another shop. Standard procedure for incompetents. Hopefully you paid or will pay the estimate fee on a credit card. If you did, contest the charge with a simple call to your credit card company. I had a Chevy dealer do $1200 worth of work on my car a few years back. They didn't fix the problem. I had it diagnosed by another shop and their charge was reversed. Always pay with a credit card in these situations.

I did use a credit card. But for $90, I'll probably eat the bench fee rather than go through the charge reverse process. I will ask for an itemized estimate before I go pick up the amp, just in case, though, based on your advice.