Bottlehead Kits > Stereomour

Channel Sudden out (A Side) [resolved]

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HeyDerAudioBob:
My Stereomour- 2A3 (I built stock in 2012 or 2013) and has worked flawlessly until today. 1 Channel sudden quit playing, powered down and waited 30 minutes, powered up, channel still dead.

Swapped power tubes, same channel dead.

Got out the manual, multimeter and check caps, looked for any obvious damage, did resistance checks, all within range. Powered up and proceeded to check voltages - started  with IA=397, IB=398 (mains are at 123.5 - 125.0v), OA=385 and rising to 392, OB=178-179. Monitored for 2 mins, no change.HLMP LEDs lit. Kreg(s) at 2.49.

Stopped here since OA was so high. Powered down, pulled C4S board and reviewed closely for any damage, solder joints gone bad, etc. Nothing obvious.

Run a E81CC tube (12AT7 went bad about 5 years), lites up like it always has but unfortunately I do not have a replacement - have several 5751 if those would be worth testing but thought I would wait for advise.

Looking for guidance, feel like it is the tube or in the C4S board. Any advice or guidance would be appreciated.

Thanks

Bob S

Paul Joppa:
I expect you're right - either the tube or the C4S. I would advise hunting up another 12AT7 - the 5751 will just make both channels silent. Fortunately it's a fairly common tube; many guitar shops even carry them.

HeyDerAudioBob:
Thank you Paul, I will do just that. Will report back once I have have one in hand tested. I do appreciate the quick response.

Cheers

Paul Birkeland:
You can rotate the C4S board 180 degrees and reinstall it.  If the voltage issue switches sides, that would indicate a cold solder joint on the center leg of the MJE5731A (most likely, or another similar soldering issue).  If the high voltage says on the same side, that would definitely motivate me to buy a new tube!

HeyDerAudioBob:
Paul and Paul,

Well the new tube did not solve the issue. I did touch up the solder joint on the MJE5731A as well as any others that even remote looked suspect. Same results. Should I replace the MJE5731A (which I will need to order) or should I consider ordering a C4s card from you guys and just install new one.

Thanks again for continued assistance,

Cheers

Bob 

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