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Antique Radio Technical Forum
The Hum From The Speaker

Posted by Lewis L on 04/13/2009 21:18

:With capacitor trimmers, 1 turn is a good place to start. However, messing around with the trimmers to get reception is pretty much shooting in the dark. Follow the advice I gave you and let us know how far you get. Start at the speaker and work your way back until you can't get a signal to go through (from your signal generator or finger). That is a logical straight-forward way of going about it. Once you can't get a signal, the trouble most likely lies within that stage. You CAN find the trouble. Aside from measuring capacitors and resistors, IF transformers should usually have from about 10 to 80 ohms resistance. FM IF transformers will generally be less than this, but you're not dealing with FM in this radio.
:This procedure will usually solve just about every "doesn't work" problem that arises on this forum.

I always start at the power supply wwith a Voltmeter and check Voltages. Then I check the audio amplifiers with an audio generator or a transistor (battery operated) with a minature phone jack plugged into the output, and connected across the volume control. These are the simpler circuits to troubleshoot. Once you have those working to your satisfaction, you are ready to tackle the RF, Osc-mixer, and the IF, 455 kHz or whatever, and backward to the oscillator-mixer, which you say you can find on a good radio. Great, that is about the hardest part of the radio to understand and repair. But first, check the audio. A finger to the center tap of the vollume control will give us all a wealth of information.

The Hum From The Speaker 
Johnny 04/11/2009 14:58 
Thomas Dermody 04/12/2009 00:16 
Ed M 04/13/2009 13:28 
Johnny 04/13/2009 19:10 
Thomas Dermody 04/13/2009 21:05 
Lewis L 04/13/2009 21:18 
Edd 04/13/2009 22:43 
Johnny 04/14/2009 07:01 
Edd 04/14/2009 11:27 
Doug H 04/15/2009 11:38 
Johnny 04/15/2009 12:01 
Doug H 04/15/2009 12:40 
Johnny 04/15/2009 17:51 
Johnny 04/15/2009 11:54 
Johnny 04/15/2009 19:58 
Johnny 04/16/2009 02:15 
The Rework Is Done 04/15/2009 23:21 

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