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Old 6th October 2003, 07:30 AM   #1
wrl is offline wrl  United States
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Default Transformer hum in leach amp

I just noticed this today. I'm not sure how long it has been going on... but there is a fairly loud hum comming from the transformer in my leach amp. (not like a hum in the speakers caused by the transformer, but a hum comming FROM the transformer)

I always noticed it right when I turned it on, but it went away after a second or so. Now it is constant, although I don't notice any excess heat and the output still sounds fine.

Does anyone know what this is, or if it is normal? Unfortunately because of the crappy outlets in my dorm, I have to use a 2 prong to 3 prong converter for the amp. Could this be causing it?

BTW, I am using the victoria magnets 8 A version toroidal transformer.

Thanks Guys,
Anything worth doing is worth doing right... and redoing to make it better... and again to fix it back the way it was.
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Old 6th October 2003, 02:21 PM   #2
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Default you may have dc in your primary

looks like you need power factor correction, or there's a dc current riding on your ac i'd go for the old fashioned ei trannie anytime....i once built a torroid trannie in the 80's but i wound it as i would an ei (in terms of number of turns) and found out that the no load exciting current was way below that of an equivalent ei trannie, so far i have not heard it humming or anything....
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Old 6th October 2003, 07:46 PM   #3
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It is normal that they hum when switched on, and then it decreases. How big is this xformer, 8 amps at how many volts? What is it driving? Is it also humming if you take off the load?

Jan Didden
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Old 7th October 2003, 05:50 PM   #4
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Default Hi

Hello there,

I once had the same problem, however, mine was caused by a diode that slowly failed. I say slowly failed because it works without hum(on speakers) but the transformer hums. The only difference in your case is that my transformer was so HOT! I changed the diodes and it works fine again.

This may not be your problem but it won't cost you anything to check the diodes and caps on your amp. Listen to the other guys suggestions, they know a lot when it comes to this things.

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