Silvertone 1482 tremolo problem

[davohilts]

I'm been working on my Silvertone 1482, replacing the filter caps, out of tolerance resistors, and tremolo caps. The amp was unplayable when I started. Now it passes signal but somehow the tremolo is bleeding onto the output. Even with the footswitch shorted i'm still getting tremolo bleeding into the signal. I've looked everything over and don't see anything amiss but I am clearly missing something. Does anyone have any idea what the do to troubleshoot??
Thanks,
Dave

[JHow]

I'm sure the gurus will weigh in, but just to clarify: when you turn down the strength control does that kill the trem like it's supposed to? Does the speed knob vary the frequency of trem oscillations? Are you saying that the amp is basically works good, but trem signal is bleeding? If you take out the trem tube then all is quiet and amp works good?

[davohilts]

The strength control doesn't seem to have any control of the trem. The speed control does work but the trem is weak. When I turn up the volume on the Microphone channel this drives the tremolo very hard and distorted and slow throbbing, very slow and very hard throbbing. Overall the amp is distorted and crappy sounding so something isn't right. It gets loud but is flabby on the low end. Pulling the 6AU6 tube stops the trem from working except when I turn up the mic volume it does the slow throbbing still. I've real confused as to what the problem is.

[JHow]

The strength control doesn't seem to have any control of the trem. The speed control does work but the trem is weak. When I turn up the volume on the Microphone channel this drives the tremolo very hard and distorted and slow throbbing, very slow and very hard throbbing. Overall the amp is distorted and crappy sounding so something isn't right. It gets loud but is flabby on the low end. Pulling the 6AU6 tube stops the trem from working except when I turn up the mic volume it does the slow throbbing still. I've real confused as to what the problem is.

If it is overall distorted and crappy sounding then it sounds like more problems than just tremolo. You mentioned you replaced filter capacitors and capacitors in trem section. Did you replace any other capacitors, like coupling caps? Have you had a look at voltages? I would wonder about leaking on grids.

[davohilts]

There must be some issue with the mic volume control circuit as the problem of pulsing begins when the control is turned up.
I have changed out all the caps and most of the resistors.
Here are voltages starting from the left when looking down inside the chassis:
v1 12AX7: P1-93.1 P3-.62 P6-101 P8-.82 (fluctuates)
v2 12AX7: P1-160 P3-60.5 P6-124.8 P8-.88 (fluctuates)
v3 6V6: P3-295 P5-32.5 (fluctuates) P8-32.6 (fluctuates)
v4 6V6: P3-315 P5-negative to .09 (fluctuates) P8-32.6 (fluctuates)
v5 6AU6A: P5-292 (fluctuates) P7-0
B+ is 315V off rectifier, 294V at 2.2K, 232 at 27K
NOTE: When I turn up the Mic. volume all the way the voltages all fluctuate and the B+ is 349-315 at rectifier, 326 to 294 at 2.2K, and 260-232 at 27K.
HV winding: 325-0-325 VAC
The more info I get the more confused I get!

[JHow]

I wouldn't expect 32 vdc on the cathodes (pin 8) of the 6V6-es - more like 17-19 volts. What is the cathode resistor value? Is it 270 ohm 5-watt? Is it one of the ones you replaced? Is it grounded?

[davohilts]

yes the cathode resistor is the original, it tests exactly at 270. I added a new 25mf 50v cap and everything is grounded. I grounded the cap to the same post as the cathode resistor, that shouldn't be a problem should it?

[JHow]

yes the cathode resistor is the original, it tests exactly at 270. I added a new 25mf 50v cap and everything is grounded. I grounded the cap to the same post as the cathode resistor, that shouldn't be a problem should it?

Wait a sec. You shouldn't have any positive DC voltage on P5 grid of your 6v6s. I re-red your post and I missed that first time. Your .01 caps should be keeping positive DC out of there. If you do have positive voltage there that is concern. I would re-check the coupling cap going to 6v6 grid.

One other thought... check your 330K resistors and your .05 cap coming out of the trem. The trem is feeding into your grids there too. If something is letting Dc in from that side that would be trouble too.

[davohilts]

by coupling cap do you mean the one that connects pin 5 of v3 to pin 6 of v4? it is a brand new orange drop but I guess it could be bad.

[JHow]

There are two going into the power amp: one from the plate (pin 6) of the PI tube and one from the cathode (pin 8). On the schemo I have they are .01 uF caps. Their job job is to pass the signal and keep the 160V and the 60V respectively out of the grids of the power tubes. If they are new and hooked up right then they are probably not the problem. The other area I would look at is the .05 uF cap that serves the same function coming off the plate of hte 6AU6 trem tube. If your measurement is correct and you have 32 V on the grid of the tube it has to come from somewhere. Also just wondering if one of your 6v6s is hosed? Sorry I'm not much help.

[davohilts]

thanks for the troubleshooting! I installed some salvaged caps from a working deluxe reverb that I rebuilt so the .05 (I used a .047) and one of the .01 caps you are talking about are used so that might be a reason. I've got some new ones that I can easily install and see what happens. First though I'll pull a couple of relatively new JJ 6V6's out of another amp and see what happens. Your help is greatly appreciated as I tend to move to voodoo electronic repair when I get stumped.

[davohilts]

The cap off the 6AU6 tube was the problem! Thanks for the help!

[Jazz P Bass]

Which cap?
The .05 going to the Intensity control?

[davohilts]

Yes, the last one I changed out!

[Jazz P Bass]

O/k.
Troubleshooting coupling capacitors.
Next time, what you would want to look for is dc voltage on the non plate side of the cap.
It is a coupling cap.
Meaning, it will block all Vdc from the plate but it will pass the Vac (signal) voltage.
If there is voltage present, the cap is bad.