Reverb Tank Issue

V

Vild

Active member
If anyone happens to know much about reverb tanks I could use some help. I have an Ampeg vh140c with what seems to be the appropriate spec reverb tank. 4bb3c1b

I've tried it both ways and smacked the tank and both sides sent audio which should mean both half of the tanks are working correctly.
I've tried both cables going straight from the in and out to check the cables and turning the reverb knob and they both work. By testing it that way it does some phasing stuff to the sound which means the amp is definitely sending AND receiving signal through it as well.
Yet somehow it doesn't work when I actually play through the tank. :(
It just makes no sense to me.
 
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Thanks for making a new thread.
It always helps if you can provide a link to a schematic. I found this one.

That's quite a beast of a solid state amp. They do all the switching with JFETs and first I'd try a patch cable in the effects loop because the loop goes into the reverb. Also check all the switches to make sure the effects loop isn't muted.
 
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Appreciate it. I should've, thankfully Ampeg has all their schematics online and thanks for linking it. Wish more companies did that. I do use the fx loop and never had a problem with it.
There is no fx loop switch but there is a reverb switch if plugged in, otherwise the verb is always on. Whenever I've tried to test it I did make sure it was on either way though.
I've had the amp about a year, I've just finally been trying to get the reverb to work and was staring at the schematic last week, tried every test I could find without opening the amp yet and can't figure it out.
 
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Effects loops often cause trouble if they rely on shorting jacks. Fortunately it's usually a simple matter to get them working again. I hopes that's what the problem is. Grit or oxidation can affect the shorting part of the jack and simply cleaning it will fix the problem. Worst case scenario is to replace the jack socket. Or you can keep a short patch cable plugged into the FX loop.
 
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Once again I use the fx loop and have never had a problem with it. Thanks though. Whenever I open the amp up I will check to see if they are nasty and rusted just in case.

To be specific though I have tested the amp reverb with and without using the loop.
The reverb has nothing to do with whether the fx loop is being used at least as far as I can tell. Also it is after the fx loop in the circuit though.
 
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Vild said:
Once again I use the fx loop and have never had a problem with it. Thanks though. Whenever I open the amp up I will check to see if they are nasty and rusted just in case.

To be specific though I have tested the amp reverb with and without using the loop.
The reverb has nothing to do with whether the fx loop is being used. Also it is after the fx loop in the circuit though.
Click to expand...
The schematic has a test point TP13 with voltages for the input to the reverb pan. If you have a multimeter, that would be a good starting point.

5469.jpg
 
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Aentons said:
The schematic has a test point TP13 with voltages for the input to the reverb pan. If you have a multimeter, that would be a good starting point.
Click to expand...

True! I've been trying to avoid opening the amp for now so I didn't pay any attention to the test points yet and have just done all the outside tests that I could find.
 
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I think the 4bb3c1b is the wrong tank for it. I think it is supposed to be a 4Ab3c1b. It has a different input impedance.

mojotone.com

Understanding Reverb Tanks: What Those Letters and Numbers Really Mean

Understanding Reverb Tanks: What Those Letters and Numbers Really Mean Written bySteve Snyder Published onAugust 2nd, 2021 What do the alphanumeric reverb tank names mean? DIGIT #1 - REVERB TYPE 8 = short tank, three springs 4 = long tank, two springs 9 = long tank, three springs DIGIT #2 -...
mojotone.com mojotone.com
 
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Aentons said:
I think the 4bb3c1b is the wrong tank for it. I think it is supposed to be a 4Ab3c1b. It has a different input impedance.
Click to expand...

Do reverb tanks for solid state amps normally have 8 ohm input then? I tried finding out what it was supposed to come with but I couldn't find any info. I even asked people in Facebook groups who have the amp and no one would check.
This tank is what it came with when I got it. But that certainly would explain why despite me testing it every way I could think of including even jumpering the rca jacks to make sure the amp is sending and receiving signal worked but the tank doesn't!
 
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Vild said:
Do reverb tanks for solid state amps normally have 8 ohm input then? I tried finding out what it was supposed to come with but I couldn't find any info. I even asked people in Facebook groups who have the amp and no one would check.
This tank is what it came with when I got it. But that certainly would explain why despite me testing it every way I could think of including even jumpering the rca jacks to make sure the amp is sending and receiving signal worked but the tank doesn't!
Click to expand...
Sorry, you are right. Solid state amps tend to use tanks with a higher input impedance. I don't see it specified in the schematic but from what I see online, other ss ampegs use something like a 4FB3A1C
 
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Aentons said:
Sorry, you are right. Solid state amps tend to use tanks with a higher input impedance. I don't see it specified in the schematic but from what I see online, other ss ampegs use something like a 4FB3A1C
Click to expand...
Oh ok so if anything it would drive the tank too easily then right?

Aentons said:
You can just disconnect the cable from the tank input and test the tip and sleeve of the cable.
Click to expand...
Right I understood. Conveniently I just bought a cheap scope/signal generator since I gotta meet the test conditions. Time to try that out!
 
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Bigger waveform was clean channel.
Nothing with multimeter.
 

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The signal generator I only set to 2v going into the front of the amp cuz I don't know how much is supposed to be going into the amp and don't wanna fry something while testing by putting too much. Just googled it and guitars def don't put out that much.
 
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Retried with .7 volts on signal generator this time for more appropriate voltage. Bigger one still clean channel, probably cuz distortion compresses.
 

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Put a 100uf capacitor in series with the signal coming out of the "reverb send" jack. Probe that output with the clip on the scope probe clipped to metal on the chassis.

Then send a 0.5V sine wave into the amp input and see what you get. If it's distorted, turn down the amp gain and see if it cleans up.
 
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