Is there any way to determine what type of reverb tank will work with a specific amp without the schematic? I have a 1970s Gibson amp with what I suspect is the wrong tank...doesn't work at all.
Thanks for your comments Zenas. The amp is very rare...a Gibson G115 from the 1970s made by CMI Electronics in El Monte California. I've tried googling a schematic but nothing comes up. It has four Eminence alnico speakers and a beautifully balanced crystalline tone.You need to know the impedance of the tanks input and output side. Hopefully that's on the schematic but it doesn't sound like you've got one anyway. Maybe if you mentioned the specific amp someone here will know what tank it takes.
Lots of other things can kill a reverb too. I've had dead ones that came back to life after just changing all the electrolytic caps. On amps that old that's always the first thing I do.
Its solid state so there's no reverb tube. I tried doing the wire switcharoo...didnt work. Thanks!Have you tried swapping the reverb tube(s)?
What specific amp and what’s the make/model of the tank?
Have you tried flopping the RCA’s around. If someone bought the right tank but have the RCA cables backwards it won’t work. One time I bought a replacement tank for an amp and put the cables on with the in/outs oriented the way the original one was (the original one wasn’t broke, I just wanted less decay), and it didn’t work at all. I triple checked to make sure I bought the right tank, figured I must have got a dud but couldn’t see anything wrong with it. Grasping at straws, I switched the RCA’s so the In/Outs were backwards and it worked! Worked perfectly normal, nothing weird. I’m not sure if the tank jacks were mislabeled by the factory or what but it worked. It’s probably a long shot but it’s easy to try and worth a shot, especially if it’s not the original tank.
Good link! I'll pull out the tank tomorrow and check both RCA jacks with a multimeter. I can fix a broken contact...but I cant fix a dead transducer.Here's some reverb tank info, that's an amp I've never worked on so I can't help much. https://www.amplifiedparts.com/tech-articles/spring-reverb-tanks-explained-and-compared
Wouldn't hurt to check the resistance of the input and output. That'll be DC resistance in ohms not impedance ohms, like a speaker the reading you get will be lower than impedance but it'll give you a ballpark number anyway. Also if it's way off like shorted or open, you'll know if the tanks just dead.
First make sure the send is sending a signal out and the return is returning a signal injected into it.Good link! I'll pull out the tank tomorrow and check both RCA jacks with a multimeter. I can fix a broken contact...but I cant fix a dead transducer.
If you look at that link I posted above there's a list of different impedances. Be nice if they were all standard! Most of my reverb amps are old tube Fenders or Ampegs, they take different tanks because they use different reverb circuits in the amps.Wait... granted I know more about RF circuits than audio, but you’re telling me people design their tanks for different impedances? I’d think that would be a standard. I guess not.
The reverb tank in my ‘80s Carvin X100B is dead. How do I tell what impedance it was designed for?
Brilliant...at least now I know I have the right tank! Thanks!I found a schematic. It indicates a 4FB2A1A.
The schematic says G-105 at the upper left of the page, but in the title box it says G105-115; presumably it's the right schematic and the difference between the 105 and 115 is just the 2x12 format of the 105.
I'd also take it to a tech if the other pan didn't work. Could be the IC that drives the reverb or any number of things in addition to caps as mentioned above.
Excellent advice...what kind of cap has the shortest life span in a guitar amp?Am electrolytic cap that old can look like new and not work well or at all. Or you might see bubbles, bumps or leaks. You can test um for capacitance with a lot of multi meters but that doesn't tell the whole story because the voltage isn't even close to what a lot if them run at. Same thing with the little ESR meters but maybe they're a little more informative. The old way was substitution and that's still the best bet. I just replace them all in old amps. Often that alone fixes all sorts of problems and makes vintage amp repair seem easy. Unfortunately it just as often doesn't, then you gotta dig in deeper and that takes awhile to learn.
Might be time to take it to a tech.
The electrolytic caps generally have the shortest life span in modern amps. Back in the 1950s and earlier any cap could be bad, but normally since the 60s it's the electrolytic caps that go bad with age. There are always exceptions though!Excellent advice...what kind of cap has the shortest life span in a guitar amp?