Crate Stealth GT50 gain channel volume loss

[David Raye]

Want to say hello everyone glad to be here. I am looking for a tip where to begin tracks my down a loss of volume on channel 2 of my crate gt50 head. Recently,I was playing the amp and had a brain lapse I suppose and pulled v2 out while the amp was still on to switch to a different brand. When I put the new tube in and started playing there was a near total gain loss on channel 2. Channel 1 works as before the tube swap. I'm not sure where to begin to test for this change. The volume loss is almost total. Turning the channel 2 master volume near full gives a small sound though it does sound like the distortion character is like always. The v2 is used as a direct- coupled cathode follower tone stack on this amp as the gain is derived from an opamp/diode setup similar to a tube screamer or other distortion type pedal. After the tone stack, the signal goes through ss reverb and effects loop before entering a tube phase inverter. If anyone who didn't fall asleep reading this too long post could advise me what component(s) could result in this type of volume loss, it would be greatly appreciated as I have used this amp as bedroom practice amp for yrs with no issues. Thanks in advance.

[The Dude]

Welcome to the place!

It's a good idea to post a schematic when you start a new thread, so here ya go.

http://music-electronics-forum.com/a...schematics.pdf

[Enzo]

First, I don't see you telling us you put the old tube back in - did we? Could be the new tube is bad.

Specific to your question,

what component(s) could result in this type of volume loss

Do not assume you have a bad component. it is all about the circuit. A broken solder connection or cracked circuit board is just as likely as a bad part. Everything in that channel is involved in making sound happen, so most of the parts in the circuit are capable of killing the sound. You may have killed a part, but that can be a trap to assume. For example, when you plugged in the new tube, you could have crushed a socket pin. (Are BOTH heaters glowing inside that tube?) The pressure might also have cracked a weak solder connection to the socket. Also pushing down flexes the board, so a solder joint nearby but not necessarily ON the socket could have cracked. Same with traces, a weak spot on the board could have cracked severing a trace. Channel switches themselves could be involved. And so on...

The way we do this is to apply a signal and ttrace it along through the channel. If the input goes through some common stages before it branches, we know those parts work because the other channel works. SO we can limit our search to the channel specific circuits.

Does V2 have good plate voltages on 1 and 6? Are there cathode voltages on 3 and 8? I see three op amps in the circuit, are pins 1 and 7 on each free of DC? Are they showing signal?

[David Raye]

I appreciate ONE of the responses I received. Of course I put the old tube back in as well as tried several others with same result. Didn't post the schem because I don't have the internet at home and borrowed a friends phone to put up the post. Was really just wondering if removing that specific tube was a definite no-no or else 'this happens' kinda thing, but really just got reminded why I stopped using forums ten yrs ago. Obviously, it still holds true that if you want kindness or common decency and not belittlement from some... you still have to pay for it. I'll take the amp to a shop when I save up and just use channel one for now and a pedal.