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Philco 91 Restore Code ?? - Printable Version

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RE: Philco 91 Restore Code ?? - morzh - 02-19-2025

Because the usable power rating of it then is (3,200/20,000)*25W= 4W.
Maybe a tad more due to the mass, but not much. You are not using the full resistor.

RE: Philco 91 Restore Code ?? - dconant - 02-19-2025

I wondered about that. Wish there was some place local to get this stuff.

RE: Philco 91 Restore Code ?? - dconant - 02-25-2025

The shadow meter in the radio is responding to tuned signals but it never goes to a very small shadow even on strong signals. Best I can get is about a 3/8 of an inch. Is that about right or should it get narrower? The 1k resistor (#14) has been replaced. Would altering the value of #14 make any difference if so higher or lower?

Also I can't get he lower end of the dial completely lined up. Off about 10kc. The low frequency compensator (#23) is turned out to where it is no longer making a difference. There is a 410pf mica (#24) across the compensator. Could that be a problem and maybe replace it with a different value. The dial is reading higher than the 10kc higher than it should. The high side is spot on.

Thanks,
Dan

RE: Philco 91 Restore Code ?? - morzh - 02-25-2025

410pF is a large capacitance to parallel to a compensator.

As for the shadowmeter....yes, 3/8" is a bit wide, but then it also depends on the station's strength.
Does it go narrower than that when fed a signal from a generator?

RE: Philco 91 Restore Code ?? - dconant - 02-25-2025

The width does not get narrower with generator.

I think I will try some other cap values.

RE: Philco 91 Restore Code ?? - morzh - 02-25-2025

If it does not get narrower with strong signal and your AVC is OK, it could veru well be that the shadowgraph's magnet is a bit weak. Not the end of the world, not even that important: I tune by ear and the shadowgraph is for show and tell mostly.

RE: Philco 91 Restore Code ?? - dconant - 02-25-2025

How do I know if AVC is OK?

For the compensator cap I settled on 330pf. Its much closer now and close enough for me. I tried lower and higher values but lost gain with them. The original cap measured 296pf with my CCC meter. New Fluke 115 is on the way.