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Dead as a doornail
#16

    Problem is SOLVED and I may be a complete idiot !   MORZH -  I went away over the weekend with my family and kept thinking about this freakin radio the entire time.   Amongst other things -  you mentioned:  "The resistor in the middle is an NTC thermistor, it starts at about 1K and drops to 100 Ohm as it heats up".     I retraced all the caps I installed and checked all the wiring.  In my first restoration of this same radio, I noticed that  I left the thermistor (see picture) in place because, at the time,  I didn't know what it was and didn't want to mess with it.  In this most recent restoration, due to me misreading the "chassis - bottom view", I wrongly thought it was a capacitor and replaced it with a .1uf CAP. I thought the thermistor was just a weird looking capacitor.   When I got back from my trip,  I re lookeded at the chassis diagram and realized what I had done.  I soldered out the cap and put back in the thermistor -  and  VOILA -  it popped to life -  the tubes, the bulb.    So in the end, there was nothing wrong with the on/off switch.   I hooked up the speaker and the antenna and already it can pick up some am stations but I will still have to align it.     You really nailed the problem - so THANK YOU for your help.    Also, thanks to BrendaAnnD for jumping in with your help as well.
   
#17

To me those thermistors, which Philco marketed as a "Tube Saver", look more like an old fashioned radial lead resistor then a capacitor. In any event when I was a teenager I had a Sentinel that was working on, so I poked around under the chassis with an ohm meter and found out what I thought was a leaky mica capacitor, which I then removed. However when I tried powering the set up it did nothing, even though the tubes all lit up. It turned out that the leaky mica capacitor was the choke resistor in the B+ supply. But it was not too surprising that I was confused, a resistor that was packaged to look like a capacitor, but Micamold was a lousy company for doing things like that anyhow, like making wax paper caps look like mica caps, all of which were rubbish.
Regards
Arran
#18

They even made resistors looking like mica caps. Dealt with one myself.
Really dumb idea....as if troubleshooting itself is not confusing enough.
#19

(10-12-2014, 08:26 PM)morzh Wrote:  They even made resistors looking like mica caps. Dealt with one myself.
Really dumb idea....as if troubleshooting itself is not confusing enough.
morzh & arran - 
OK - so now at least I feel  a little better that I'm not the only one to have made this type of mistake.  Thanks guys !




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