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Philco 640 - Need Some Help - Printable Version

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RE: Philco 640 - Need Some Help - Geoff - 07-01-2016

(06-30-2016, 10:06 AM)Steve Davis Wrote:  Next, place another radio next to the radio under test to see if you can tune the local oscillator of the nonworking radio.

Steve

I think I already know the answer to this but do I need to use another antique radio or will a modern portable work? I would think a modern portable would be fine.

RE: Philco 640 - Need Some Help - Radioroslyn - 07-01-2016

Answer is yes. Put it near the 6a7. Set it's dial at 1000kc. tune the Philco to 1460kc and if all is well you'll hear a hiiss in the portable. Tune the Philco a bit as it may be a little off in frequency.

Terry

RE: Philco 640 - Need Some Help - Geoff - 07-02-2016

I tested the voltages on the 6A7 on all 4 bands to see if the band switch had any issues. Got the same voltages regardless of Band:

[Image: http://i12.photobucket.com/albums/a241/JoeRadio1938/Miscellaneous/ScreenHunter_175%20Jul.%2001%2021.52_zpsth2lb2s7.jpg]

Hooked up a signal generator, red lead to grid cap of 6A7 (cap removed), black lead to chassis ground, 460 KHz. I did hear the tone at the speaker loud and clear.

Next I tried putting a second radio next to it, but first I tried it on a working set to know what to listen for. Used my Zenith 9-S-262 set to 1000 and used my TransOceanic B600 and was able to hear the quiet spot around 1460. I verified it was the quiet spot by turning off the 9-S-262 and the regular background noise returned on the B600. I also adjusted the dial back and forth on the 9-S-262 around 1000 and the quiet spot would fade in and out on the B600. Tried it on the Philco 640 and could not hear a quiet spot.

RE: Philco 640 - Need Some Help - Geoff - 08-04-2016

Finally figured out where I went wrong. I mis-read resistor #50. It is supposed to be 25K and I had 250K. Also, I had resistor #51 in parallel with #41. It should have connected from #50 to capacitor #54. Works fine now.

Philco 640 Shadow Meter Bulb Type - Geoff - 08-04-2016

The literature does not call out the bulb type to use in the shadow meter on my Philco 640.  The original that was installed was a screw type that did not work.  However, you did not actually screw the bulb in place.  Also, I could not read a number on it.  Does anyone know which one I should use?  Here are some photos from different angles:

[Image: http://i12.photobucket.com/albums/a241/JoeRadio1938/Miscellaneous/ScreenHunter_103%20Aug.%2004%2015.52_zps5t9ahc5l.jpg]

[Image: http://i12.photobucket.com/albums/a241/JoeRadio1938/Miscellaneous/ScreenHunter_101%20Aug.%2004%2015.52_zpshzpipbsk.jpg]

[Image: http://i12.photobucket.com/albums/a241/JoeRadio1938/Miscellaneous/ScreenHunter_102%20Aug.%2004%2015.52_zpswlfz3hb9.jpg]

RE: Philco 640 Shadow Meter Bulb Type - klondike98 - 08-04-2016

Chuck says you can use a #46 lamp. See: http://www.philcorepairbench.com/tips/svctip01.htm

(I moved the post into the rest of the 640 thread you have going)....

RE: Philco 640 - Need Some Help - Geoff - 08-04-2016

Thanks!