Troubleshooting Open Coils - Philco 84B - Printable Version

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+--- Thread: Troubleshooting Open Coils - Philco 84B (/showthread.php?tid=9273)

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Troubleshooting Open Coils - Philco 84B - bdi1976 - 04-10-2014

Hi fellow members-
I am new to radio restoration but have been quickly learning about the process (although I have restored a couple of cars). I purchased a Philco 84B as my first project and am currently replacing the caps, resistors, and bakelites. I am slightly confused about troubleshooting the coils. For the oscillator and antenna coils, I get very low resistance values (2-8 Ohms) while checking continuity. I cannot locate the theoretical values and am hoping these are high enough values to indicate working coils(??)...does anyone know where can I locate these values for an 84? Also, the voice coil and output transformer shows OL so they appear dead. How do you guys figure out if these are good or need rewinding if you get values which are not OL or very high? Should I just assume they are OK and proceed with the rebuild? Thanks for your help-
-The schematic is attached
bdi

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RE: Troubleshooting Open Coils - Philco 84B - skyscraper - 04-10-2014

Hi, welcome to the Phorum!

Exact resistances of the rf/if coils aren't important, as long as they aren't open. Your range of 2-8 sounds fine.

The field coil should measure 1140 ohms, the primary of the output transformer should be 400 ohms, and the voice coil .9 ohm. If any of those are substantially off or open, the radio isn't going to work. The speaker can be replaced with a modern one, and output transformer, and a resistor close to 1140 ohms at 20-25 watts or so. Hum may be increased without the field coil acting as a choke.


Good luck!

Will

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