Philco 40-165 - Printable Version

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+--- Thread: Philco 40-165 (/showthread.php?tid=16759)

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RE: Philco 40-165 - jmcgill - 06-11-2017

Once again your expertise is invaluable.
The power transformer secondary resistance reads a little low.  The schematic has half the secondary at 420 ohms and the other half at 400 ohms.  I get about 300 ohms on one side and about 345 ohms on the other.  The primary reads 18 ohms just as the schematic says it should and the filament windings read <.1 ohm.  Should it be replaced or is it within tolerance?

Einstein once said, "I have no special talents, I am only passionately curious."

Jim

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RE: Philco 40-165 - Radioroslyn - 06-11-2017

Wouldn't lose any sleep over it. Would measure the ac voltage @ the rectifier plates (without the rectifier in place) to see if it's close. Then leave it on for a little while to see if the transformer get hot.

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RE: Philco 40-165 - jmcgill - 07-26-2017

I have searched for a 270 ohm resistor the schematic calls shows, however, no matter how many times I trace the old wiring I come back to a 470 ohm resistor that looks as if it was put in after manufacture.  The soldering on the leads is shiny and sloppy.  The after market notes I have do not indicate a change however my notes are probably incomplete.  Should I replace the 470 with a 470 or replace it with a 270 the schematic indicates?
Thanks...Jim

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RE: Philco 40-165 - Radioroslyn - 07-26-2017

For now I'd leave it. What it does is set the - bias voltage for the 41 and 7C6. THe important part is when you get it working measure the - voltage on pin 4 of the 41. RCA sez you need about -15vdc there. If you lower the resistance you will low the amount of bias voltage. If you do change it you'll need a 3-5watt job to replace it.

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