DRBILL Posted January 10, 2003 Share Posted January 10, 2003 The old man is stumped! I just rebilt a DYNA MK-IV. It had a bad filter capacitor which I replaced. The choke tests good. I still have a VERY faint 120 HZ hum, rich in harmonics. Through any other speaker than Klipsch, you probably wouldn't notice it. Anybody have a suggestion? The original cap was 20-20-20-30 (no longer made). The substitute is 20-20-20-40. The 40 is the first stage that feeds the choke. My inclination is to hang another cap across the 40 under the chasis. If so, what value? BILL Quote Link to comment Share on other sites More sharing options...
BEC Posted January 11, 2003 Share Posted January 11, 2003 Bill Do you have access to an ESR Capacitance Meter? I think I would check the Cap you just put in for excessive Equivalent Series Resistance. An electrolytic can be bad (on ESR) even it a regular capacitance meter tells you it is good. Just a thought. Bob Quote Link to comment Share on other sites More sharing options...
WMcD Posted January 11, 2003 Share Posted January 11, 2003 Very much a shot in the dark. Are you sure the rectifiers are working properly. Also chassis connections all round? I just can't help but notice that you're jumping to the conclusion it is a problem with the new cap. How many other connections were rebuilt? This is not a comment on your skills. I've often solved one problem and, in the process, created another. Gil Quote Link to comment Share on other sites More sharing options...
DRBILL Posted January 12, 2003 Author Share Posted January 12, 2003 BOB & GILL, et al It had to be an "burning-in" situation. It gradually abated, then vanished completely over a week's heavy use. We may never know. Thanks for your suggestions. BILL+ Quote Link to comment Share on other sites More sharing options...
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