Dead as a doornail - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Dead as a doornail (/showthread.php?tid=10704)

---

RE: Dead as a doornail - ODPILOT - 10-12-2014

    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.
   

---

RE: Dead as a doornail - Arran - 10-12-2014

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

---

RE: Dead as a doornail - morzh - 10-12-2014

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

---

RE: Dead as a doornail - ODPILOT - 10-13-2014

(10-12-2014, 09:26 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 !

---