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Tube DIY Asylum: Is this a problem or is it normal ? by Audiodyssey

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Is this a problem or is it normal ?

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I recently acquired a Fisher K-1000. The unit hadn't been powered on in many years, wasn't working properly at all, and so I replaced every capacitor in the amp. Before this, it was pulsing at about 1KHz which I found very weird, but that issue has since been solved. One channel wasn't working, that issue, also resolved. The amp works and sounds good, at least on a pair of very cheap, inadequate test speakers.

The possible issue I see now is when I monitor the unit on a metered variac while playing music, the current reading meter needle (in milliamps/amps) swings with the music (mostly bass beats). These transients are roughly 100-200 milliamps by my estimation. It would seem to me that this has to be altering the final product from the speakers in some way...?


I do not have a scope or signal generator or the knowledge to use them. I am interested in first knowing if this is what is called SAG, and of course I am interested in putting a stop to it. The unit is solid state rectified by means of 3 HV diodes and one diode for the bias supply. Would I be looking at the diodes or power supply capacitors as the cause for the sag? My elementary knowledge tells me to increase the capacitance for the B+

Any insight would be greatly appreciated.



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Topic - Is this a problem or is it normal ? - Audiodyssey 08:23:30 09/20/20 ( 4)