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Help, TL072 based spring reverb Crate V16 Palomino won't turn down

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paulj0557

New Member
Hi, I recently bought an all tube guitar amp, except with a solid state spring reverb driver. It is a very well taken care of U.S. designed and built around 2005-2010ish CRATE V16 PALOMINO 1-12" COMBO AMP. Schematic > https://elektrotanya.com/PREVIEWS/63463243/23432455/egyeb/crate_palomino_v16.pdf_1.png

The problem I am having is since I briefly, as in a few seconds tried to attach a different, known working, for-solid-state longer (by a couple inches) reverb tank to the Palomino's IN/OUT Jacks it made a brief crackle sound and no reverb function, so I immediately detached it.

Upon reattaching the original spring tank the REVERB LEVEL ADJUST POTENTIOMETER DOESN'T FULLY SILENCE THE REVERB WHEN IT IS TURNED DOWN...it still sounds the reverb about 50% of full reverb. Not only this, but the reverb knob at full clockwise max is much more intense, "goes to 15". It's almost as if everything shifted , min 0 now=5 and max 10 now=15.
Note- The potentiometer itself has no problems
Both channels of the TL072 opamp do have output, and no diodes,resistors or capacitors around the entire reverb driver circuit have failed according to my DVM.

I did experiment adding 700ohms to 1k FROM TERMINAL ONE on the REVERB POT (P6) to GROUND. The results do lower the minimum setting, quieting the reverb level, but it comes at the cost of lowering the max level to around 6-7. I'm looking for a better solution.

Any help with this is very much appreciated, - Paul
 
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It sounds like one side of the Reverb Control, P6, is not grounded, one end must be grounded for it to have any effect on the signal.

Craig
 
When I went to bigger springs on mine, I had to go to accutronix and search out which one was the proper fit, electrically. As I recall there was a four letter code...I don't remember the details but I matched it up to my Palomino...It was a nice step up.
 
llwhtt said:
It sounds like one side of the Reverb Control, P6, is not grounded, one end must be grounded for it to have any effect on the signal.

Craig
Click to expand...
The ground on the pot is fine. Like I said , it turns down, just not all the way. Plus I also ran an alligator clip from P6 terminal 3 to ground, plus i checked for continuity through the pot. It's all good.
 
fredgarvin said:
When I went to bigger springs on mine, I had to go to accutronix and search out which one was the proper fit, electrically. As I recall there was a four letter code...I don't remember the details but I matched it up to my Palomino...It was a nice step up.
Click to expand...
Yeah I'm still baffled. The springs I tried I know were from a working solid state source and I have used them in a few different reverb applications and they never caused a malfunction or part failure. I'm beginning to think that it was just a parallel unrelated conundrum. I might just change the opamp and the two or three low voltage electrolytic caps. The original springs are fine.

I'll measure the PICKUP COIL AND DRIVER COIL RESISTANCE and compare to candidate springs as well.
 
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