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Philco 42-PT-2 candohm - Printable Version

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Philco 42-PT-2 candohm - brotherfan - 07-22-2016

If you look at the schematic for the Philco PT-2 the candohm lugs, part 27, should NOT have a resistance path to the chassis, correct? I get about a 3 to 4 meg ohm resistance reading at each of the 3 lugs and the chassis, but this shouldn't be, right? I'm going to rebuild it anyway, but I just want to confirm my thoughts that any connection to ground shouldn't be at those lugs.

RE: Philco 42-PT-2 candohm - klondike98 - 07-22-2016

Welcome to the Phorum!
Icon_wave

Your link to the schematic didn't seem to be working so I modified it ... seems OK now.

No...there should not be a path to the chassis from those lugs.

RE: Philco 42-PT-2 candohm - Radioroslyn - 07-22-2016

Hi BF and welcome,
In the big scheme of things 3 to 4 megs doesn't amount to much resistance. I think what you are seeing is the IF trap #5 .2mf and coil. Heaters working ok?? Burn out dial lamps??
I resently had a PT-61 that Iwas fixing for a friend and the resistor does generate some heat. Was thinking about replacing it w/a diode.

RE: Philco 42-PT-2 candohm - morzh - 07-22-2016

Disregard Megaohms.

RE: Philco 42-PT-2 candohm - Arran - 07-22-2016

 Unless the resistor is disconnected from the rest of the filament string, whilst reading a 3-4 meg Ohm reading to the chassis, then I would disregard it. The main issue with these candohms is open connections between the terminals and the resistive wire inside. But the ones used in AC/DC sets like the PT series are low value with maybe one tap for the pilot lamp so they don't tend to fail as much as the large ones with multiple taps used for voltage dividers in AC sets, nor does anything catastrophic happen when they do since the tubes won't light.
Regards
Arran

RE: Philco 42-PT-2 candohm - klondike98 - 07-23-2016

Arran, Terry & morzh know a heck of a lot more than I do so I'd listen to them on this one! Keep us posted on progress.

RE: Philco 42-PT-2 candohm - Kenneth F. Besso Jr. - 07-23-2016

just had one in a Emerson 59 Ch--- 2 taps on it,,,read 500 ohms,,,,here it was short out to the frame of the resistor,,,didn't figure it out till ,,I took the leds off to check it,,this one was bolted to the chassis,,,Cheers

RE: Philco 42-PT-2 candohm - codefox1 - 08-06-2016

Candohms can be troublesome if there is crud or leakage from a bad filter capacitor, etc... Rig up a substitute resistor train and see if that solves the problem.