Philco G978

[dtvmcdonald]

I'm new to this forum, and almost new to vintage electronic restoration, but not that new to vintage repair.

I recently got a nice 1959 model Philco G978 AM-FM radio. Its a very very
odd mechanical thing with the dials on top, speaker in front,
and chassis vertical, the tubes pointing to the front. Seven tubes,
selenium rectifier. It works actually fairly well as-is, but is a tad weak
and shows hum on AM only. Remarkably the dial calibrations
are spot-on.

A few questions:

1) is there anywhere I can get a schematic without paying money?
I found several for sale online.

2) It appears by inspection that the only electrolytics are in the usual
can. Since its printed circuit with no parts below the board, I think I'll
just remove the present one electrically and place tubulars behind
the board. Does this sound OK?

3) more bothersome is the selenium rectifier. The current one
works fine and does not get more than barely warm. But after
too many episodes of H2Se gas poisoning in my youth due to
bad ones, I'm going to leave it in place but electrically use
a Si diode. Presumably this means a dropping resistor. Is the
best way to calculate the resistance to measure the DC voltage
drop and (after disconnecting one end) the (DC) current, and calculating from that? Of course its AC so perhaps I should add a 1 ohm resistor
in series and measure the (instantaneous) voltages across the
1 ohm and the diode with a (differential) scope and calculate the
resistance from that? What do you people do?

4) The safety line cord, the kind that is attached to the bottom
with a plug that comes undone when the bottom is removed to
replace tubes, is dried out and dangerous. Is there a good place to
get replacements (polarized)?

5) Are the small capacitors that isolate the FM antenna
terminals from the chassis (possibly hot without a properly
working polarized plus) "safe" or should I add a pair of
recent ceramic ones in series with the wires?

Doug McDonald