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Greetings all,
Just developed an issue with one of my monoblocks - after turning on a few days ago, at the end of warmup (right when it should have reached operating conditions, couple of minutes after turn on), fuse flips. I flipped it over, take power tubes out, leave all others in, and disconnected components off of the PS as follows:
1. Transformer only (nothing connected downstream) - no blow, correct AC voltages out;
2. Attach tube rectifier - no blow, correct voltage out (also, the JJ GZ34 measures fine in my B&K 500; BUT - as far as I know the B&K 500 parallels triodes/diodes, so I do not know if both diodes in this tube are perfect);
3. Attach SDS board (with nothing attached to it) - fuse blows immediately at the onset of warmup.
I unsoldered all components on the SDS board and checked: caps check OK (used DMM, after a brief rise through kOhm range it settles at "OF" MOhm, which with my DM usually means infinite resistance); resistors measure drifted from 330kOhm to 220kOhm (???), except for two, which measure at 330kOhm. Now, the SDS board should come populated with 330kOhm resistors per design (but it wouldn't be the first departure from design in the TE kit; for instance, caps are 100uF instead of 68). I do not know for a fact that the guys at Triode Electronics sold me two 330 and six 220. I would have to double check color codes on them to see if they drifted (if they should be the same value per color code but are different now due to some failure), or are mistakingly picked and are indeed 220/330 per manufacture (I don't have the amp with me right at this moment). BUT - to my mind a difference from 220k / 330k is insignificant in this position. Bottom line, I don't know if I should nail down defect to be at these resistors or should look further.
At the same time, everything checks almost perfect (unless I'm missing something) but failure is catastrophical (blown fuse every single time I turn it on).
At this point, I'm assuming my test procedure for capacitors does not reveal some finer failure and I further assume that the 85C rated caps reached end of life early due to too high a temperature inside this amp. It's the best explanation I can come up with.
Any suggestions would be greatly appreciated.
Best regards,
Radu.
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