KLH Model 21 found at Goodwill today!

[jr_tech]

Since the IF board is shielded, I can't see if the active devices are transistors or ics.

But first things first, regardless of the type of device used for IF amplification, IMHO, the hum problem needs to be resolved before further problems can be addressed.

jr

[Captainclock]

Originally Posted by jr_tech

Since the IF board is shielded, I can't see if the active devices are transistors or ics.

But first things first, regardless of the type of device used for IF amplification, IMHO, the hum problem needs to be resolved before further problems can be addressed.

jr

Well if the filter capacitor wasn't the cause of the hum (it still hummed even after the filter capacitor was replaced) what else could cause the radio to have a 60 Hz hum?

[Ed in Tx]

Post 9 jr tech mentioned the rectifiers. My thought too. You checked both of those?

[jr_tech]

My first guess was on post 9 (bad power supply diodes), but there are additional filter caps on the audio board to check/ replace. Shorted output transistors could also place a hogh load on the power supply and cause hum.
Does the volume control change the loudness of the hum or is it always there?

jr

[WISCOJIM]

Is the hum still there when the volume is all the way down?

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[Captainclock]

Originally Posted by WISCOJIM

Is the hum still there when the volume is all the way down?

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Yes the hum is there no matter what the volume level is at even when the volume is turned completely down. and like I said whatever is causing the hum noise is also I'm sure causing the unresponsive tuner issue as well.

[WISCOJIM]

Sounds similar to this one: http://audiokarma.org/forums/index.p...mmmmmm.525449/

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[WISCOJIM]

Or if they are already too messed up, they can be carefully drilled out. I've had to do that many times over the years.

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