79 super reverb woes strange distortion

[Bluzzi]

@Bluzzi - none of that is right about a Super Reverb. Master Volume had a pull boost on later amps, and there is only one speaker out, with an extension speaker in parallel.

@Jasonpatrick - schematic shows 500V on the CT - https://www.thetubestore.com/lib/th...er-Reverb-Ultralinear-1978-1981-Schematic.pdf - gotta get that extra wattage somewhere!

Check out his post after yours. He had a pull boost on it and removed it and just replaced the Master volume pot. So both were correct. You are right about the 2 outputs and I didn't imply there wasn't but yeah don't know why I said one was 2 and the other 4ohm. Since in parallel you should not use another 2 ohm speaker as it would bring the impedance almost to a short at that point. But he wanted to know if the problem was stock speakers. Hence unplug the stock speakers and use the 8ohm one he had to test if he wants to eliminate the stock speakers as the problem.

 

[judge74]

Thanks for everyone. I know it has been a week or two so here is my update.

I fixed the odd distortion fuzz sound. I replaced the .01 coupling cap after the master volume, and I replaced both .1 caps after the phase inverter. I figured if it was an odd sound that affected both channels then it had to be around the phase inverter and I started by swapping caps and that fixed it.

What I have now is a pretty great sounding amp if you use the normal channel... I can turn it up on the normal channel and the speakers seem fine. regrettably there is a loud 120 hum / white noise in the tremolo channel. the sound of the hum gets louder and softer with the trem channel volume knob. It is also affected by the trem channel tone controls, you can eq the character of the hum . I have piles of 12ax7s and swapping tubes at v2 does not help.

I figure since it is affected by the eq the problem is either in the eq or earlier....

Here is what I have done so far to try to fix it. I replaced the 250 pf cap in the reverb channel tone circuit, I replaced all 6 of the 100k plate resistors in the amp, I reflowed the solder joints on the board that have anything to do with V2. Of course this is in addition to all the work I did replacing all the electrolytic caps and other stuff I mentioned earlier. I am trying to figure out what to try next.... Tube socket maybe?

 

[judge74]

Here is an overview of where we are at. Everything highlighted yellow has been replaced. Everything circled in red was just removed. The problem I am still having is hum in the vibrato channel which is affected by the volume and tone controls. Goes away when I pull V2, is not helped by swapping V2 and V1.

One question I have about the schematic is the purpose of the two resistors circled in blue. Do they do anything not related to the pull boost circuit? should I have removed them when I removed the pull boost?

 

[Pete Farrington]

The 1k resistor should be replaced with a wire link.