Silvertone 1484 with very quiet distorted output

[prs_matt]

New tubes did not solve. I did some research and think I narrowed it down to coupling caps and plate resistors around the PI--or maybe the OT. Both channels have the same problem. The OT is new so I dont really suspect it yet. I recently read a post on another forum that says R34 could go open and cause this problem. It is on my list of suspects already so I will check it out.

My first check was on C13 because I found 14V on the grid end of it. I failed to look at the cathode end of the triode though and see that there is +/-125V there so the 14V on the grid is OK.

Am I on the right track?

[John]

Matt, the only help I can be is that my old Harmony had the same problem. Since I wanted a project I replaced all the caps and some of the resistors throughout - except for the big filter caps (they were fairly new already) and it "solved" the problem.

[eleventeen]

Do you know if your output section is working? Any way you can inject a decent sized signal one or two tube sections before the 6CG7 PI? Let's say...at the wipers of the volume controls for a start.

Bias volts OK? Near spec @ -36 v?

6L6 cathodes aren't connected to....ANYTHING (except for each other??) Or is there a dot missing where their connection crosses ground? I don't think I've ever seen that. How can those tubes gate B+ if there is no connection to B+ ground? (Stupid question 49-B)

On a Pro Reverb I have that has been hotrodded with 2 add'l 6L6, lifting their cathodes from ground takes them out of the circuit! Somehow, this (eg; this lack of ground connection) is an impossibility. What's your voltage on those cathodes?

Continuing with the troubleshooting...cheesy standby switch not really opening?

How are your other points of B+? You have that kind of goofy stacked dual voltage doubler power supply....I'd make sure that was working right before going to to signal components.

[SoundmasterG]

The schematic has several known errors on it for these amps. One is the triode for the oscillator....the pins are not labelled correctly. The other is a connection shown between R35 and R36 to ground. That connection to ground is incorrect.

These amps used very poor quality resistors, so replace them and your problem may very well be solved. The coupling caps used (brown blobs) weren't the best either, and replacing them with just about anything will work well and sound better. If you have a scope you can measure the signal as it goes through the amp and find the problem that way. If you don't have a scope, then you can try the pop test to spot a weak tube or stage.

Greg

[prs_matt]

I replaced R34 and C13 so far. I trace the voltages from stage to stage backwards from the PI and find nothing amiss. All voltages are from 5 to 10V below those on the schematic so no worries there. There was a larger discrepancy across R34 so I replaced it and voltages came back up to about 9 under schematic voltages.

So far none of the coupling caps are showing leaks (no DC on the grid end) so beyond tone improvement I dont see any reason to suspect them based on tests.

I don't have a signal generator so I can't inject signal in any fashion other than touching each pin and listening for a pop as the meter probe makes contact.

I am going to call Weber and see if they have had any problems with their replacement Silvertone OTs as that is what is in there.  As for the OT, I am seeing correct voltages at the CT and the 6L6 plates. Is there a definitive test for faulty OTs?

[LooseChange]

Just clip another OT in there in it's place. It does not need to be a match. Just be careful.