Hi, I have big hum in my radio. I asked some question before about hum and troubleshoot tips. I check some signal in my radio with my scope. I want to know what is hum when view in a scope. 1 mV p-p ripple, 10 mV, 1 V? It's a sine or sawtooth wave? I have a sawtooth wave before choke of speaker and little sine after. I know I will not have a true DC, but what maximum ripple is acceptable?

Thank you!

Hi J-F

You will see a few mv or more hum on an oscilloscope. The amount will be determined by location in your radio circuit. You want that little sine wave after the speaker choke to be as small as possible.

Replace electrolytic filter caps. There will be one on each side of the speaker choke (field). They dry out in time and allow hum. If you are unsure of the value use 10 mfd @ 450 volts.

Norm

:Hi, I have big hum in my radio. I asked some question before about hum and troubleshoot tips. I check some signal in my radio with my scope. I want to know what is hum when view in a scope. 1 mV p-p ripple, 10 mV, 1 V? It's a sine or sawtooth wave? I have a sawtooth wave before choke of speaker and little sine after. I know I will not have a true DC, but what maximum ripple is acceptable?
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:Thank you!