Hello all and thank you for accepting me into the group. I have not done any DIY amp work but willing to learn and very desperate at this point.
I own a 12-year-old Cayin A 88T integrated amplifier which I bias regularly. The last time I tried to bias the tubes I decided to clean the tube sockets with a 3M electronic quick-drying contact cleaner. I waited an hour before opening the amp to ensure it was truly dry.
I opened the amp, turned the biasing pot to the minimum, and turned on the power. When I checked the initial reading on the multimeter 3 tubes were at 0 and 1 had a 1400 reading in the multimeter. I shut it down immediately and waited 5 hours to check again. Same result but now the other tube on the same left side was reading 200 while the whole right side was still 0. Can someone please just give me an idea of what to check, replace, buy?
Thank you so much.
I own a 12-year-old Cayin A 88T integrated amplifier which I bias regularly. The last time I tried to bias the tubes I decided to clean the tube sockets with a 3M electronic quick-drying contact cleaner. I waited an hour before opening the amp to ensure it was truly dry.
I opened the amp, turned the biasing pot to the minimum, and turned on the power. When I checked the initial reading on the multimeter 3 tubes were at 0 and 1 had a 1400 reading in the multimeter. I shut it down immediately and waited 5 hours to check again. Same result but now the other tube on the same left side was reading 200 while the whole right side was still 0. Can someone please just give me an idea of what to check, replace, buy?
Thank you so much.
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Right, I'm not familiar with your amp but it seems like everything was ok till you applied the 3m "cleaner". This may have left a coating that is retarding contact between the valves pins and base contact's. First I'd try using some Isopropyl alcohol to remove any residue. Personally I just use a drill bit of the right size to clean valve base contacts &/ or just a little squirt of ether based cleaner.
That aside it could be you've disturbed something else like a wire that supplies bias voltage, if you can make a lamp limiter so that when you next apply power the current is limited, that would help prevent any catostrophic FU's . I also monitor bias with a DMM when I first power up any amp I've worked on to make sure that bias is applied: no bias, hit the off SW.
Andy.
Sorry for the weird font change, fecking computors.
That aside it could be you've disturbed something else like a wire that supplies bias voltage, if you can make a lamp limiter so that when you next apply power the current is limited, that would help prevent any catostrophic FU's . I also monitor bias with a DMM when I first power up any amp I've worked on to make sure that bias is applied: no bias, hit the off SW.
Andy.
Sorry for the weird font change, fecking computors.
In any case, let's us know what did you measured: Volts, milliamperes, ohms? Where? Loaded or not? Signal incoming or not? A schematic or user/service manual will help us to help you.
3M™ Novec™ Electronic Degreaser
3M(TM) Novec Flux Remover, 12 oz Can
3M(TM) Novec Contact Cleaner, 11 oz can
3M(TM) Novec Contact Cleaner Plus, 11 oz Can
3M(TM) Novec Contact Cleaner/Lubricant, 12 oz Can
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