Quote:
Originally Posted by cameronflyer
Vaveforms were my next stop on this journey. I have to unpack my test leads when I get done with work today.
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Frankly if it were my set, I'd do it with a redneck signal injector!
Take a small 600v capacitor, say an .005MF and hold one lead in your hand and touch the other end to the cathode (the video is cathode injected in this set) of the 7JP4 CRT and you should get a 60 cycle hum in the picture. If it is very weak, try reversing the AC plug, as that either will increase or reduce it.
Then follow the signal back to the plate of the 6AU6 Video AMP, and then to the grid of the same tube.
Then go to the plate pin 7 of the 6AL5 Video detector, and then to pin 1, the cathode.
The 60 cycle hum your body is picking up should modulate the IF stages, too, so follow it back.
You are looking for the point where the signal disappears, which sure makes finding the problem easier.
When the hum gets too strong, switch to a much smaller capacitor.
(If the signal is too strong, it may jump the defect.)
Oh, and remember this is a hot chassis set, so use due care.
Back in the late 1950's when I was servicing TVs, I used to keep several value small caps with a brass washer soldered on one end hung up on a nail above my workbench, just for this purpose. I covered the lead between the cap and the washer with spaghetti to lessen the chance of an accidental contact with the set.
James