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Ella: Red Hot Tube

PostPosted: Mon Mar 16, 2009 5:52 am
by usul01
Hi All,
Although I bought the Ella kit circa 2004, I only got around to completing it recently and it has been running fine (and sounding superb) for around 3 months (using Valve Art 6550 tubes and upgraded Audio Note PIO capacitors). After a listening session over the weekend, the inside right tube began to glow red hot, with a lot of hum in the right channel. I swapped tubes around but it effected all tubes plugged into the same position. I disassembled, removed all tubes and checked the voltage on pin 5 of all the tube sockets (which should be at -50 VDC). All were at -50 VDC except the offending tube position, which was around +270 VDC (ouch!). I tracked the circuit back from that point and found that the associated Audio Note capacitor had "shorted" with everything else appearing to be ok. Given the high price of these capacitors, I would have expected a very long and trouble free life. Are they usually prone to fail so quickly or could it indicate a more fundamental issue with the amp? Any clues as to what other tests/checks I should carry out to verify the root cause of the issue.
Thanks for any help you can provide. Cheers.