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Philco model 70 rebuild - by Tim P.
#78

I "took" an hour and did some more troubleshooting. I have thought several times I had it narrowed down, but it keeps eluding me. Now - m a y b e ... I have really narrowed it down. I removed the RF tube - eliminated that thing. Still have the osc tube out, so it is disabled. I inject the signal at the grid of the 1st detector tube at the 260kc IF freq. I connected the signal tracer to the grid of the 2nd detector/1st af tube. I also have Fluke meters connected to the voice coil of the radio speaker and signal tracer speaker - it can see what my ears cant hear. At this point, the tracer follows the radio. I moved it to the grid of the IF tube. At this point, the tracer does NOT follow. It stays steady, the radio fluctuates. I just finished tracking voltages on the IF tube, plate-screen-cathode. Dont notice any changes following the fluctuations in volume (and mild static).

I overcame killing the signal on the plates when meter is connected by cranking up the sig gen. I have to wait for things to cool again, then I am going to connect the tracer to the plate of the IF tube and see it things track or not, next is the cathode of the 1st det tube. Still need to track voltages on this tube.

http://www.philcoradio.com/tech/images/70a.jpg

Dumb question - when I did the IF alignment, I didnt have a freq counter, now I do. I think I aligned the IF at something close to 263kc instead of 260. I havent corrected this yet. May not be an issue - but, after that stinking tube shield fiasco - ... ??? I dont want to mess with that until I have this intermittent resolved. Unless ... ??? this IS the problem???

Yea, Mike - years.. I hope not.

If I could find the place called "Somewhere", I could find "Anything" Icon_confused

Tim

Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44


Messages In This Thread
Philco model 70 rebuild - by Tim P. - by TV MAN - 01-29-2014, 11:46 AM
RE: Philco model 70 rebuild - by Tim P. - by TV MAN - 04-26-2014, 09:53 AM



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