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loomis 22nd March 2006 06:20 AM

Anything post power transformer that can cause it to hum / buzz?

In an old tube integrated amplifier, are there any components after the power transformer that could be bad and cause it to hum? In other words, can bad caps / tubes etc cause the tranny to hum?

You can hear the hum within 2 feet of the transformer. There is no hum out of the speakers. The amp is wired correctly.

Transformer hum occurs no matter where amp is plugged in: at home, work, friend's house, ect. Transformer bolts are tight.

Or is this a case where the windings are bad and that's all there is to it?


lndm 22nd March 2006 08:12 AM

Large current swings translate to large magnetic flux and this means flexing of the xfmr laminations.

I don't know if this is your issue, but leaky electro's could be causing it. If your amp is old, replace them anyway.

loomis 22nd March 2006 10:33 PM

You see I am trying to determine if the transformer is bad *before* I waste money buying replacement parts. If there is no possibility of new caps etc fixing a humming tranny then I won't bother. Instead I'll look into the loose lamination issue.

Nordic 23rd March 2006 04:54 AM

Tried disconnecting the secondaries and just powering it up yet?

ivegotmono 23rd March 2006 10:39 AM

I've got an Eico HF-81 and the power transformer hums for a little while after it's turned on but then goes away as the caps charge up. I've been told that the original power transformers on those were undersized. I had a HF12 that vibrated all the time and it was the rectifier tube going bad.

ray_moth 24th March 2006 02:55 AM

Yes, a heavy load on the secondary can cause a buzz in the power transformer core. As the man says, check your elecrolytic smoothing caps, and anything else that could be causing excessive current drain.

loomis 24th March 2006 05:25 PM

Sounds like a plan. Will check out electrolytics and rectifier tube. Thanks.

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