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RE: Futterman H-3 restoration

Wow! That is a real bummer!!!

Just yesterday my transformer began an annoying buzz when powered up. I immediately shut down and inspected the internals for loose parts or anything out of the ordinary - nothing. Subsequently the amp powered up with no problems. Later that evening same thing and this morning no problem.

On review of the circuit diagram and reflection of prior experience I suspect a problem with the PS bridge rectifier network. The original parts are four 1N2484 600V 750ma and pretty old tech. Also in my amp the main filter cap was bad. I believe that the diodes where going bad but not quite failed due to the old cap. The diode recovery time may have been compromised whereby loading the transformer. However because of the intermittent nature the problem still has me puzzled.

I'm going to replace the old diodes with new 1N4007 and if I have the proper capacitors on hand, add snubbers to the bridge.

Also if you haven't done so replace the single diode on the secondary power supply located before C15 with a 1N4007.

Can you provide me with company that's rewinding your PT along with the specifications?

Thanks 33dot33rpm


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