Carvin Series III X-Amp

[Gtr_tech]

yep....replace the relay then. If yer brave you can pop the cover off (if it is removable) and de-ox the contacts. I don't like all that other crap running off the bias tap....if they wanted low voltage for op amps they shoulda used a seperate winding like they did on the later versions.....just a fiasco waiting to happen.

[lowell]

Yes that's the one!! Enzo, you're the man, thanks. I'll try that Gtr_tech thanks.

[Enzo]

Cool. The old wall of bookshelves pays off again.

One of these days I will finish inventorying these schematics.

[lowell]

Ok so the relay was not at fault. I checked the reverb circuit per the schematic and there were a few components in the opamp circuit w/ incorrect values. When I had disconnected the coupling cap to the reverb circuit the distortion went away so i knew the reverb was causing a problem. Changing the values to those on schem fixed it! Thanks Enzo and Gtr_tech.

[lowell]

Ok so this amp came back w/ some new problems... or old problems. Anyway it had a lot of hum. I tried a few things to locate the hum: a new set of power tubes, checked bias on both sides, replaced coupling caps to power tubes. I pulled PI and that got rid of it. I thought it MUST be in the PI. So then I was testing the PI circuit and finding nothing. I was about to give up on this hum until I got my signal tracer out. I pulled the PI and there was a tiny hum on both grids which was a lot louder on the plates. This did not make any sense to me. I had excluded the PA from causing the hum as w/o the PI the hum was gone. I touched the bias feed as it was directly connected to the area where the hum was being injected. I got a fair amount of hum. I then touched the bias filter cap and BAM there was TONS of that hum. So I replaced the entire bias circuit w/ new diode, cap, resistors and that fixed it. This was odd to me as I checked and rechecked the output current draw and the negative voltage on output grids and all seemed well and good. This was a new lesson for me as I've never experienced the bias causing hum issues. Just thought I'd share as someone in a similar situation may benefit from this.