I have a Parasound HCA-855a which has mechanical hum. I've isolated this to be the amp and an authorized repair center confirmed the amp needs a new transformer which is $300 plus labor.
Due to the amp's age, I would simply replace it but there's a problem - I absolutely love the amplifier's sound and have not found another amp I like this much since purchasing it years and years ago. Also, my dream amp, Halo 5 channel is outside budget parameters.
Any thoughts?
Due to the amp's age, I would simply replace it but there's a problem - I absolutely love the amplifier's sound and have not found another amp I like this much since purchasing it years and years ago. Also, my dream amp, Halo 5 channel is outside budget parameters.
Any thoughts?
Maybe you can find a less expensive transformer. Are you sure it is not the filter caps? They can cause the best transformer to hum.
Another possibility...
The diode bridge might have one open diode. The amp would still operate, but the transformer would buzz pretty well, and max output power would be slightly diminished.
I looked for a schematic on hifiengine, but I could only find a user manual...so I can't give more detailed guidance...but you could disconnect the secondary wires of the transformer...if it continued to buzz badly, then yes, it's the transformer. If however, it quieted down, it might be just the diode bridge.
Good luck.
Dan
The diode bridge might have one open diode. The amp would still operate, but the transformer would buzz pretty well, and max output power would be slightly diminished.
I looked for a schematic on hifiengine, but I could only find a user manual...so I can't give more detailed guidance...but you could disconnect the secondary wires of the transformer...if it continued to buzz badly, then yes, it's the transformer. If however, it quieted down, it might be just the diode bridge.
Good luck.
Dan
Maybe loose laminations if it is an E I type. Take lots of photos of where and which wires go to where. Remove the transformer and use yacht varnish or potting compound to re seal the loose laminations.
If you know of a transformer factory/workshop with varnish and an oven, ask them to re seal it for you.
It could be adjusting the lamination bolt tension will stop it.
If you know of a transformer factory/workshop with varnish and an oven, ask them to re seal it for you.
It could be adjusting the lamination bolt tension will stop it.
Some pictures would be useful so we can advise better. Caps going bad can cause resistance and load the transformer. That will also show up as a lower output voltage making it appear to be the transformer. If you can measure the output of the transformer and then disconnect it from the bridge and remeasure that will go a long way toward diagnosing.
Is this detailed enough or should I take some additional pictures?
An externally hosted image should be here but it was not working when we last tested it.
While it's on and buzzing try tightening (or loosening) slightly the nut in the centre of the toroidal transformer and see if that helps.
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