Crate Palomino V32 head - problem Help!

[Ufologo22]

Hi guitar friends,
I have a challenging situation. I live in West Palm Beach, Fl. I'm the owner of a second hand Crate Palomino V32 tube head. I have an issue that the local amp shops can't resolve in decent time (2 months wasted at a shop only to tell me the pot is custom made and hard to find).

The volume pot of the clean channel doesn't work, it's in full volume all the time. It started one afternoon, I heard a 2 second crackling noise and then it's been on full volume since and a little noise. Prior to this, there was always sound bleeding from the clean channel volume pot on Zero. The volume in the dirty channel works fine but something is wrong as I hear some noise/interference. The EQ works, I hear frequencies changing but something is off.

Crate sent me a new clean channel volume pot, I installed it but the problem continues.
I checked for continuity with a ground point and the volume POt, there is continuity.
I replaced the preamp tubes but nothing, same issue.

I love the sound of my crate but there is no point of owning if no one local wants to fix in time. My electronics nowledge is minimal; however, I've put together 2 distortion pedals from parts following tutorials and trying to decipher schematics. I'm not confident handling/discharging high voltage caps yet, but can follow instructions if someone guides me.

Here is the schematic:

http://www.thetubestore.com/lib/thet...-Schematic.pdf

Help anyone?

[Dave H]

Crate sent me a new clean channel volume pot, I installed it but the problem continues.
I checked for continuity with a ground point and the volume POt, there is continuity.

It looks like the ground connection to the pot is open either inside the pot or on the pcb. You've changed the pot but it is possible that the new one has been damaged by excessive heat. Measure the resistance between ground (chassis) and the pot wiper (centre terminal). Turn the pot fully ccw (min volume). You should see the resistance drop to zero.

[g1]

The most important thing with regard to the high voltage caps is to measure with your voltmeter to make sure they are discharged.
This model has a bleeder resistor so you just need a little patience and a safety check.
Unplug the amp from the wall, then turn the standby switch to the play position. Leave it for 10 minutes, then measure for DC voltage at the standby switch. Meter black probe to the metal chassis, red to the standby switch. Check at both sides of the switch. When it is discharged you should have very near 0 volts DC at both sides of the standby switch.
In addition to what Dave H mentioned above, there is a possibility the bright cap, C52, is shorted. That would bypass the vol. pot.

[Ufologo22]

Ok, just a quick update. I replaced Capacitor C52 (120pf) along with c37 (50pf). The problem remains, it didn't fix it, although I have to say that after I replaced C37, I immediately heard a little less noise.

Right now they dirty channel is back to normal, but the clean channel has this loud "interference/ground/hum", same constant pitch kinda sound. Volume pot acts as a filter and is very loud.(not change in volume level).

I checked the value of the volume pot and ground, I get continuity at it tests fine.

Any other indication i could follow?
Your input is highly appreciated.

[52 Bill]

I checked the value of the volume pot and ground, I get continuity at it tests fine.

Take a jumper wire and connect the volume pot center terminal wiper directly to the chassis ground. What happens to the noise and signal?

[Ufologo22]

Hi There, I'm back and I'm still alive (not electrocuted). For the record I have replaced the following capacitors:
C52 (120pf)
c37 (50pf)
volume pot (1M)
I was finally able to run a jumper cable from the chassis ground point into the center terminal. The clean channel still has a very loud and BASSY sound. Removing the jumper cable to the chassis and moving the volume to 0 gives me the same Loud and Bassy sound, however, the volume pot is now acting as a volume pot, it just goes from LOUD to UBER SUPER loud along with a noise in the background.
I also connected the footswitch and noticed that when I engage the "Volume Boost", the clean channel squeals, I hear the dirty channel but a loud squeal along with it.
The Clean with Boost just changes it from "Loud" to "Louder". The volume for the dirty channel is working correctly.

Any suggestions are welcome!

[1ampman]

I had a Peavey with the same problem. It turned out the high voltage B+ caps were worn out and not filtering. Channels would bleed through the power supply to the power section.... Recap the bitch. It's a nice amp other wise.....

[SoulFetish]

I'm suspicious of the optocouplers. Try this, take a jumper wire and connect the wiper of you volume pot to ground again and at the same time take another jumper wire and connect the wiper of your gain pot to ground. What happens? If you get no sound, remove the jumper from you clean volume and see if it works as it should. Report back.

[SoulFetish]

Also, looking at the schematic, it looks extremely similar to the Crate V30 (which I owned for a number of years). Mine was the combo amp, and I can tell you some areas which almost certainly will end up in failure, if it suffers from the same piss poor ventilation in the chassis and cabinet enclosure that the combo amp suffered from.