Crate GX-80 reverb repair question, wrong new tank...too much reverb

[Slobrain]

Hey all,

I had a bad reverb tank on a crate GX80 1x12 combo and tried matching the old tank in the accutronics catalog on the input/ output ohms of the old tank in the amp. apparently I ordered the wrong tank, I got a 8BB2A1b 3 spring tank, the old one was a 2 spring tank. With the new tank its waaayyy too much reverb so I need to return the new tank to amplified parts. I cannot tell the original part number on the old tank and am a loss. Can anyone help? Not sure what to do now... Thanks

[g1]

What were the in and out ohm measurements?

[Slobrain]

The input is 28.1 ohm and the output is 202.0 ohm which in the accutronics book shows a 8BB2A1B as a cross... Where did I go wrong?

[Slobrain]

I just measured the new tank and its output is 214.1 ohm , its also a three spring tank and the old tank was a two spring.

I just seen on ebay a crate GX60 with a tank number 1BB2C1A so I wonder what that crosses too? my old tank had part number 79-201-02 but I don't have a crate cross reference book to go by. Originally I went by the ohms to order a new tank but I guess I was wrong...

[g1]

The 2 spring equivalent would be 4BB2A1B.
I didn't think the extra spring would make such a pronounced difference to the reverb sound. Did you hear it work properly with that old tank?

[Enzo]

The extra spring makes a more complex reverb sound, not more OF it.

I am surprised your original pan did not have the number stamped on it.

I see you ordered BB2A1B. That A means something different from a C there. I suspect your problem might be that the op amp driving this pan is not happy about the grounding.

[g1]

If that is a MOD tank that you got, you can alter the ground scheme inside. Remove the solder jumper at the input end.

[J M Fahey]

Modern (Op Amp driven) tanks often have a floating drive coil , so they ground through a small resistor (usually around 22 ohms) and you get current drive, which sounds better.

IF you bought a tank with grounded input coil, that grounding shorts the 22 ohms current feedback resistor, drive Op Amp gets full blast and might cause what you hear.
It should also distort (the reverb sound) easily.

But it should be very easy to correct it at the tank itself.

Maybe the drive female RCA connector is insulated (just to simplify mass assembly) and when needed they add a short wire to ground, easy as a pie to clip it off, *or* RCA body is grounded (usually riveted) , in that case I'd pull it (Dremel rivets off) and reinstall using a cardboard washer or something.

Of course, don't restore ground again when reinstalling.

Personally I'd rather do that at home (10/15 minutes) than wait 1 week or more for Mail both ways, but of course it's your choice.

Please post a couple closeups showing both sides (in/out) of that RCA connector.

[nickb]

This might help.. How to Change The Grounding

[Slobrain]

Well guys, I removed the ground from the input just like you said and (BOOM) great sounding reverb, probably better than this amp had before. Its an old amp but the clean sound is good and it sounds so much better with a good working reverb. Thank you all again. The ground problem I missed and its due to my lack of knowledge with reverb pans... I new thing I will have to read up on...

Another old SS amp ready to rock America...

[Slobrain]

This might help.. How to Change The Grounding

The new reverb pan was a mod brand so just like in the site you posted it was exactly like that, I just unsoldered the jumper, good for the company for making it like that. Thanks for posting that site too.

[Enzo]

They make it that way so they only have to make one style of pan. They can then make it any of the ground schemes after teh fact by adding teh jumpers.