Hello Ralph (@atmasphere),I'm posting this here so others can share your response; apologies if there is a more appropriate place to ask.I just bought a pair of M-60s, built as II.2s but upgraded by you in 2008 with a PS boost; they have just one switch and one pot on the front. I cannot get the output to null on either unit, so I am wondering how to proceed. I checked all output tubes for blown tiny fusible links near the base, and indeed found one ( but only one ) bad tube. Even if I remove a tube from the other side of that unit, output will still not zero. On both units, I have to turn the pot fully CCW to get a minimum. On one unit it's down pretty close to zero, on the other one closer to mid-scale.So: 1) is it safe to run the amps unbalanced, at least for a little while?2) without a tube tester, how do you suggest I find bad tubes? For example, could I start with just one tube on each side and juggle tubes until I get a balance, then try for 2 on each side, etc?Thanks!
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@crowdaddy2 Insofar as I know, the best way to find a failed tube is trial and error: you should have a second full set on hand anyways. If replacing all the tubes doesn't work, send back to manufacturer for check-up. Ralph and Atma-Sphere will be glad to evaluate the problem. I don't think anyone can really tell you what the problem is without physically evaluating the unit. Best wishes! |
I swapped tubes between sides until I got a good null on each unit. As advertised, the M-60s do sound great: most noticeable immediately was better localization of sound sources. Will take a gamble on some $20-a-pair jugs from Ukraine; perhaps if I precondition them they will last a while. Am thinking of building a uTracer: https://www.dos4ever.com/uTracer3/uTracer3_pag0.html Very clever tube curve tracer, over 1800 built so far. |
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