| Author | Message | ||
     Cyle Ritchie (cyleritchie) Username: cyleritchie Registered: 05-2012 |
I have some bleed coming from somewhere. I replaced the filter caps and the caps on the rectifier board. This is a SS model. I still have a buzz under the tone on hi or lo and the buzz is there on standby. Any suggestions? | ||
| Lars Verholt (lmv) Username: lmv Registered: 11-2009 |
Hi Cyle, if we assume that your standby switch works correctly, there should be no B+ on the output tubes and hence no sound whatsoever coming out of the speaker in standby. Do you still hear the buzz if you unplug the speaker from the amp? If you do, you need to start checking voltages in the amp to ensure that the power supply is operating correctly. You could have a faulty standby switch that could cause some peculiar symptoms. Sincerely, Lars Verholt www.captain-foldback.com | ||
| Cyle Ritchie (cyleritchie) Username: cyleritchie Registered: 05-2012 |
It's not a constant buzz. It's a faint distorted undertone of whatever you happen to be playing in Hi or Lo & you still hear it on standby. | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Do you hear it JUST after turning it to standby? What I mean is, does it continue to do it for a long time or just a few seconds? The caps COULD be charged up and just take time to disipate the voltage or does it do it after several minutes of playing on standby? Mike. | ||
| Lars Verholt (lmv) Username: lmv Registered: 11-2009 |
Sounds like you have crossover distortion going on. Time to check for leaking caps. Sincerely, Lars Verholt | ||
| Cyle Ritchie (cyleritchie) Username: cyleritchie Registered: 05-2012 |
It never goes away. Like I said, I've replaced the filter caps and the caps on the recto board. I'm gonna try replacing the electrolytics on the preamp board to see if it helps. If not, I'm wondering if it could be some sort of bias issue, I've never had it checked. | ||
| Lars Verholt (lmv) Username: lmv Registered: 11-2009 |
Hi Cyle, yes - the bias may need adjustment. The only way to get to the bottom of it is to get a 'scope on it. Anyway, if one of the coupling caps before the driver transistors is leaking (as in DC leakage), adjusting the bias may not solve the issue. A few mV offset caused by a defective cap makes a relatively large difference in this particular amp design. Cheers, Lars Verholt | ||
| Cyle Ritchie (cyleritchie) Username: cyleritchie Registered: 05-2012 |
Hopefully, changing the blue electrolytic caps on the preamp board will do it. If not, it's for sale. | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
With all the work you've already put into it, THAT would be a shame. | ||
| Cyle Ritchie (cyleritchie) Username: cyleritchie Registered: 05-2012 |
It's leaking DC voltage to the Chassis, just can't figure out where it's coming from. | ||
| Cyle Ritchie (cyleritchie) Username: cyleritchie Registered: 05-2012 |
Still searching | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
How much dc voltage are we talking? A few mV or a crapload? | ||
| Cyle Ritchie (cyleritchie) Username: cyleritchie Registered: 05-2012 |
All 16v | ||
| Cyle Ritchie (cyleritchie) Username: cyleritchie Registered: 05-2012 |
Finally changed the caps on the preamp board, cleaned the bias pot and set the bias. All better. | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Good-glad to hear it. Did it clean up all the bleed? Mike | ||
| Cyle Ritchie (cyleritchie) Username: cyleritchie Registered: 05-2012 |
Yep. Like new. Now I need a back panel |