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View Full Version : Revern circuit on a Crate Palomino V32H head


mica
12-07-2008, 04:42 PM
Hi,

I have a similar post on the amp & Cab forum, but when I saw the title of this forum I realized that this is probably the one I should have posted to.

Can anyone help me identify the reverb circuit components on this amp? The reverb makes a lot of loud crackling noise after the amp has been on for a few minutes. I'm pretty sure its the reverb as the noise goes away if I turn the reverb down. Someone on the other forum suggested that I check the connections to the reverb tank (that wasnt it) and then check the reverb circuit. Thanks..........

greasykid
12-08-2008, 11:48 AM
If you see an op-amp on the board and a few caps and resistors around it, that's probably the reverb circuit.

tlpruitt
12-08-2008, 12:11 PM
The reverb in that amp does use opamps (An NE5532 and a TLO72).
As stated above, check to make sure the reverb cables are plugged in and secure.
The effects loop send and return jacks are switching jacks. Sometimes the switching contacts on the jacks can get dirty and make poor contact when nothing is plugged in. That could create some crackle and weird noises.

Could also be a bad solder joint or any component that heats up like a tube or a socket or a plate resistor or something in the power supply.

Here is a link to the schamatic with part labels:
http://www.blueguitar.org/new/schem/misc_amp/crate_v32_palomino.pdf

mica
01-30-2009, 09:35 PM
Finally had a chance to open up the amp. I dont believe the circuit provided in the link is for the V32 head, at least not the one I have. One difference I see is that the circuit shows 4 op-amps while I only see 2; one TL072 and one NE5532.

I've seen people recommend replacing the op-amps, especially the TL072, any one have any experience with this? Was wondering if its worth the effort..

DcinDc
02-01-2009, 01:23 AM
It's worth it to replace the reverb tank.

Your problem sounds like a bad component in the circtuiry though. Probably a small cap.

tlpruitt
02-02-2009, 11:36 AM
Finally had a chance to open up the amp. I dont believe the circuit provided in the link is for the V32 head, at least not the one I have. One difference I see is that the circuit shows 4 op-amps while I only see 2; one TL072 and one NE5532.

The TL072 and NE5532 are both "dual" opamps, meaning that a single TL072 contains 2 opamps. Same for the NE5532.

In the schematic IC1 is the NE5532 dual opamp and IC1:A is one of the opamps in the NE5532 and IC1:B is the other opamp in the NE5532.

IC2 is the TL072 dual opamp of which IC2:A is one of the TL072's opamps and IC2:B is the other.

You will only see one TL072 and one NE5532 on the circuit board but each one contains 2 opamps as indicated in the schematic.

mica
02-03-2009, 09:42 PM
Thanks for straightening out my confusion on the op-amps! now it makes sense. On the suggestion that it is likely a small cap, is there an easy way to test if a cap is good or not?

mica
02-06-2009, 08:03 AM
I suspicious of a particular capacitor, C47 on the diagram, but the wires are encased in clear rubbery stuff. Does anyone know if there are any tricks to getting this stuff off the circuit board? I didnt want to try and just scrape it off for fear that I might damage something.

tlpruitt
02-06-2009, 08:17 AM
It is probably silicone glue/sealant. You can usually slice through it with something sharp like an exacto knife or a razor blade. The glue is typically used to keep certain components in place and prevents them from vibrating.