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Howdy,
What would be the effect of swapping the input & output cables on a spring reverb tank? Would it still produce an effect? Could it damage the electronics?
The amp we're discussing a solid-state design.
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09-28-2023 12:54 AM
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The reverb won’t work. It won’t break anything. Google “reverb tank polarity" if you need more extensive detail/explanation.
Originally Posted by WimWalther
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".. the reverb won't work."
Meaning.. won't work correctly or won't work at all?
Point of this, I have an amp (the same Polytone that's been taking up my time) with very low reverb output. At full gain its only just noticeable.. and there's no mad clatter if I rock / bump the cabinet. They use a Hammond tank, iirc.
I'm thinking the I&O leads may be reversed, but I didn't want to risk damage by just swapping leads as a test
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SFAIK, it won't work at all, but testing that by reversing the leads won't cause damage. Seriously, google "reverb tank polarity." One of the things that pops up is info about polarity of the wires themselves (i.e., reversing hot and ground wires on one of the connectors). Conceivably, this could cause the effect you're experiencing. But so could the thing simply being broken in some way. Originally Posted by WimWalther
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The tank could be broken, the connectors could have corrosion, or it could be something else. If you reverse the connectors, it won't work at all. I suggest cleaning/reseating the connectors, as a quick and easy check.
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I'd already done so, thanks. It didn't provide the level of assurance I like to have before proceeding into unknown areas. Originally Posted by John A.
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So you're willing to believe random strangers on the internet?
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Excellent point! Originally Posted by sgosnell
I suffered with an unusable Ampeg Reverberocket for years. It would be intermittently crackly. Spent a lot of money on techs. Turned out to be the reverb tank connectors. The little wings on the plug weren't making good contact with the jack on the tank. 10 seconds with a pair of needlenose pliers fixed it.
I got lucky. While replacing a capacitor as suggested by an on-line amp expert (which may have been sensible, but wasn't the problem in this case), I accidentally wiggled the line to the tank and figured it out.
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Not per se. But I've become pretty good at sifting through information from various sources, comparing it to my own knowledge & observations, and proceeding from there with a reasonable degree of confidence. Originally Posted by sgosnell
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OK, when I get home I'll reverse the in/out connections on my amp. If I die from doing this, I'll let you know. If you don't hear back from me tomorrow, assume everything went fine. Originally Posted by WimWalther
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Ha! Originally Posted by John A.
I'd be curious to know what you get, but a lot will depend on the input & output impedances of your specific model of tank.
The I & O transducers in a tank are basically the same design, with differences in the number & gauge of wire turns, size & mass of the core, etc. I'd expect to hear a reverb signal regardless of how it's connected, but with significant loss of level and fidelity with the leads reversed.
Maybe we'll see!
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I would try reversing the input output cables. Should cause no harm. If everything else is good, You can get some sound if the cables are reversed, but it is very little reverb. So that could well be your issue. I have bought amps that were great deals because the reverb leads were reversed and output low. It could also be an incorrect reverb tank, the impedance is wrong. If you are getting some reverb it could well be reversed leads or incorrect tank. take a multimeter and measure for continuity and impedance.
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Pickup coil is disiconnection by driving force.
I was experienced and recoil myself.Last edited by kawa; 09-28-2023 at 11:53 PM.
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Don't be touching it when you turn it on and be prepared to pull the plug if it starts to smoke. Unlikely, but don't ask me how I know.
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"It" being what, now? Originally Posted by rpjazzguitar
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I doubt it's the wrong tank. The tank is installed beneath a layer of yellow fiberglass(?) batting which appears 100% original and undisturbed.. fwiw. Originally Posted by Billy Z
ETA: Measured the connectors at 204R and 35R. I can't read the markings due to the insulation batting, but I think I can assume the lower figure is Input and the higher is Output.Last edited by WimWalther; 09-29-2023 at 02:53 AM.
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If there is no reverb at all , it could be one of the leads going to the either the drive coil or pickup coil. The wire leads are very thin and can break from vibration. Those can be resoldered. If either coil is open, then you’ll need a new tank.
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As I said previously, there is some reverb with gain at full. And while I have (relatively) very little git amp experience, it seems to be much, much less than expected.. Originally Posted by Billy Z
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"It", being the amp. I'd use the switch on a plug strip and be ready to turn it off.
Very unlikely to be necessary or maybe even less likely than that, but costs nothing to do.
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Swapping the leads shouldn’t be dangerous unless there is a serious defect in your amplifier. Manufacturers tend to avoid running high-voltage lines outside of the chassis where stumbling fingers might contact them.
However, you will have a huge impedance mismatch on both sides, which will cause it to sound poorly.
Tanks should be marked “input” and “output.” That’s from the tank’s perspective. Current tanks usually also have color-coded insulators on the jacks. From memory, white is input, red is output.
Check your cables. Swap out for a known-good set.
As was mentioned earlier, the leads to the transducers are delicate and can break. Has the amp been dropped?
Here’s a good explanation of reverb tanks:
http://electricalfun.com/WorkbenchFun/reverb_tank.pdf
I know you said you have a solid state amp. In a tube circuit, the reverb driver transformer isolates the tank from high voltage. A short in the transformer could lead to this. But you should have other issues if this is the case.
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Swap the leads. If that doesn’t help then you probably have a bad drive transistor or bad recovery transistor. I have not looked at the schematic for your amp but all the solid state amps I am familiar with don’t use a transformer to couple to the tank input .
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Because you have some reverb , that indicates you have continuity in your signal path. I suppose a very high resistance due to corrosion of the input / output jacks is possible. Unplugging and reconnecting should improve the signal if that is the case.
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The tube stuff was more directed at rpjazzguitar.
Solid state, yeah, drive/recovery transistor/chip. But first check the easy stuff - cables.
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Unfortunately the schematic I have does not match what's in the reverb circuit of this amp. Schematic shows a balanced driver circuit, but the amp has a single-ended driver.
Need to see if I can find one that's appropriate.
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Here's a schematic with a reverb circuit that seems to be very similar (in general) with the circuit in my amp. It uses a complementary pair of BJTs to drive the tank and a 4558 opamp to recover the signal.
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