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In Reply to: RE: Ella - right tube fiery orange glow posted by mikey115 on June 28, 2009 at 06:51:01
i finally got around to checking the voltages. following brian's manual - chapter 10, these are what i got:1. checked power tubes pin 5 - brought each up to -50v.
2. checked heaters on power tubes - from left to right - 6.44, 6.45, 6.44 and 6.46
3. middle tunes 6.5v and 9 pin tubes the same as well.
4. B+ is 441v
5. checked output caps at the point where the 10k resistor meets the bias pcb board - from left to right -50v, -50.3v, -50.8v, and -50.4v [Rasim: im not supposed to get any dc so these figures are not good?]
6. popped the power tubes back in and this is where the 1st tube started getting weird. i could bias the other tubes to .4vdc [el 34s] but the first tube had the numbers in my dmm skittering all over the place. i could not get a fix on this. swapped tubes, same problem.
Edit: found out it was a grounding problem - the rca ground for the probe was not in tight contact with chassis. fixed this and it the bias readings are find now.what should i be doing next? thanks very much for any help in diagnosing this anomaly.
Edit: i popped in some 6550 tubes and the amp is working fine but would still appreciate any insights.
Regards
mikey
Edits: 08/23/09Follow Ups:
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