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69.236.99.108
I called the shop and he says the Jolida 302A needs a new volume pot. He said it would cost about 80$. I explained to him that the tubes were not holding a bias. I dont see what the hell a volume pot has to do with a tube holding proper bias. I do know that the volume pot was pretty crappy and not the best. I'm hoping it is a just a stupid pot. Maybe the batteries were low when I checked the bias. I hope I dont get screwed. It seems good mechanics/techies are always too easy to get ripped off from. He claimed the caps and resistors were fine but...I know that I did a sloppy job soldering when I did the triode mod. I'll assume my joints are all good if the tech says so but I'm going to be furious if I can't get a steady bias out of my tubes.
Follow Ups:
And if it was an high frequency oscillation, inaudible in your speakers, but which would disturb your amplifier ?
while making unsteady your bias measurements ? simple hypothesis
that used to work on Heathkit gear, I immediately got defensive when I saw poor soldering workmanship. Main reason is that it indicated that there could be all sorts of things wrong that could be attributed to my work. Just so you know......you should have mentioned to him about your mods when you presented the amp to him for repair.As for the diagnosis he's presented you, I'll not comment. I assume that you've cleared it with him that he would be working on a piece of tube gear that has had one or more mods on it and that the bias doesn't seem to hold, according to your own diagnosis with your own meter(s). He should have a background in tube gear, of course, which is like trying to find an auto tech that understands carburators......
I was trained in engineering school to be skeptical of everyone elses diagnosis, measurements and designs until I had satisfied for myself what the problem is/was.
If you don't like his diagnosis, I recommend you pay him for his time and find another tech - fast. If he's a pro, he'll accept that arrangement with a smile.
Cheers,
David
Hello, Send an E mail to this guy and get his thought. James spent a bunch of years as Audio Design Engineer at Radio Shack in the 70's and 80's and is pretty sharp as well as honest.He rebuilds gear for me for the last couple years. He is pretty straight up!
Regards,
Darrell
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