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Vintage threads from the first ten years

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Re: 6V6GT troubles

8/28/2000 6:12 PM
Peter S
Re: 6V6GT troubles
Changing filter caps is not hogwash. The electrolyte dries out and the caps will eventually short. I've seen plenty of amps that needed a cap change, but still had eletrolytic with a good form on them. They don't neccessarily have to start humming before they short. I had a vintoid freak bring me his precious treasure, and tell me not to change the caps because the amp didn't hum. I told him the caps are only designed to last ten years and now that they are over 20 years old you are living on borrowed time. Well wouldn't you know how sad and pathetic it was when the caps finaly took out the Power Tranny a year later in a ball of smoke? Changing filter caps is neccessary preventive maintenance, better yet, you can even do it as forecast maintenance.... change every 10-12 years. It's dirt cheap insurance.  
Peter S
8/28/2000 8:50 PM

Yeah Peter, My thinking is the same as yours; that's why I posted about the tech saying that old FP Mallory's were somehow so much better than other caps that they would still be good after 30yrs? I didn't know if these were oil caps or not? The Mallory's I have are different in that they don't have a date code?  
I am a strong advocate of maintaining vintage amplifiers by changing all electrolytics.  
8/29/2000 3:46 AM
Steve A.

Well wouldn't you know how sad and pathetic it was when the caps finally took out the Power Tranny a year later in a ball of smoke?  
    Without getting into the vintage issues of how to accomplish this, I was just wondering if adding a fuse to the PT CT would have saved the PT when the filter caps went bad. I noticed that the AC30RI has fuses coming out the wazoo... in addition to the mains fuse there is one on the 5V FT and one on the B+ coming from the rectifier (plus one on each leg of the 6.3v FT). Guess those stories of old AC30's catching fire must have spooked Marshall a bit...  
Steve Ahola
8/29/2000 5:49 AM
Peter S

Fuses are good. You can never have too many. I use HT fuses as well as the primary one. In most cases I think that's sufficient. A fuse on every secondary wouldn't be a bad idea. Even with fuses though shorts can eat trannys.  
I don't like dead shorts to happen if I can prevent it. That's why I think anyone who tries to pinch a few bucks to push electrolytics much past the forecasted life expectancy(ten years) of use is playing with fire. Same goes for power tubes. As far as keeping the amp all original inside, well that's great for a museum could always disconnect the power cord so nobody can power the amp up, put it in a glass case a marvel at it's beauty. For player amps...completely original innards is an impossibility.  
Peter S
8/28/2000 9:08 PM

"If Leo were alive today, he'd be turning over in his grave."
No he wouldn't, because he wouldn't be in a grave if he were alive.  

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