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HELP! Magnavox 9303 transformer hum. HELP

T

TayRey520

New Member
Ok I'm hoping someone knows what's going on here. I have a Maggie 9303 power amp that I have been using for a year or so. Just recently, I plugged it turned it on and everything was perfect. After about 40 minutes of listening the transformer starts buzzing/humming. It's strictly in the transformer. Not making its way to the speakers. I've tried unplugging other things around the house, trying different outlets, new tubes, and even having nothing plugged into the inputs of the amp. Without fail about 30-40 minutes in...IT HUMS/buzzes. Anyone know what is going on?? It's driving me crazy.
 
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Is this in restored condition, or all original? I half wonder if you've got a dying power supply cap that is causing the transformer to load down.
 
gadget73 said:
Is this in restored condition, or all original? I half wonder if you've got a dying power supply cap that is causing the transformer to load down.
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It is restored. I have a JJ multi section 40/20/20/20. I can't imagine it would be failing already. It's less than a year old.
 
If it's a mechanical kind of buzz, the laminates could be vibrating or the bolts might need to be tightened down. Either way if it is working properly and not over heating or smoking or any such thing, it's probably ok. My AMP 175's transformer has started to buzz a little but it doesn't really bother me as I know its spot on the voltages and it never gets very hot.
 
The 175 I have had came with the cap can replaced and the trany hummed. I found a solder blob that was grounding out one of the cap lugs to ground. Is your choke getting hot also?
 
Lavane said:
The 175 I have had came with the cap can replaced and the trany hummed. I found a solder blob that was grounding out one of the cap lugs to ground. Is your choke getting hot also?
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The choke is definitely getting warm. But I guess I never really paid attention to the temperature of it until now. One of the terminals on that cap is awfully close to the chassis of the amp. Is it possible for it to be arcing? I mean we're talking about 1/16 of an inch close. I have already tightened the bolts on the tranny itself. Didn't do anything.
 
cademan said:
Try removing the rectifier tube to see if the transformer still buzzes.
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Transformer still buzzes. I brought over my dads amp so I could compare things. Basically the same amp except his is a 9302. I plugged his in and rectifier flashes white for a split second and rings. What in the world is going on?
 
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What you witnessed with the rectifier tube is quite normal with the 5U4 family of rectifier tubes. If voltages are normal, then most likely the noise is simple mechanical buzz. Most transformer use a wooden wedge internally to tighten the coil form to the lamination stack. It may have worked its way lose over the years allowing the coil form to buzz.

Dave
 
Something about those long filaments on the 5U4 get "jangly" for lack of a better word. I've got several that make that noise.
 
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