[sumnerplace]

Can anyone tell me what the coil for the oscillator in a 91 looks like and how its constructed? I have a radio that is missing one... So I have some old coils from other pulls that I can use as a form but I need to know how to wind it. Thanks in advance...

[radio1]

Are you referring to coil 19 on schematic? Looks like a series plate fed Hartley (?) oscilllator hitting the 410 pico section there, you might substitute a newer oscillator coil producing the correct IF for the next section if you cannot find the original..

[sumnerplace]

Yes, the coil is No. 19.  'So where would I find a modern coil that would yeild me 260 Khz  IF freq?  'the ones they sell at 'AES are for 455 KHz.  so I need one that could go from 810 fo 1860 Khz not 1001 to 2055  right? Or do you think the modern ones will go down to 810 without a prolblem?
ThANKS,
BOB

[Ron Ramirez]

You should be able to pull a suitable oscillator coil from any of the following Philco radios:

19, 71, 89, 91

All four use the autodyne oscillator circuit (with a type 36 or 77 tube) and were designed for a 260 kc IF frequency.

A 91 or 71 junk set might be harder to find but there should be plenty of 89 junkers out there. Of course, you can count on having to rewind the outer winding which is almost always bad.

I'm not aware of any newer oscillator coils designed for a 260 kc IF frequency.

[Radioroslyn]

For the folks following at home: https://philcoradio.com/library/download...%20129.pdf

I doubt you would be able to get an osc coil design for a 455kc IF to tune down low enough to use it at 260kc. That's just shy of 200kc. It's got a slug but maybe it will adjust 20kc not 10x that. Adding more capacitance across the two tuned circuits may work. But at some point the C overcomes the L and it doesn't work. At 200kc I thinking your past that point. 

Philco didn't use the 260kc IF in very many of there sets. Most are right around the same time frame as the 91. Like one version of the model 90 did and I think the 200X may have. You can go there the alignment data and look for the 260kc IF.

Wouldn't think about changing the osc and IF to 455kc because then you will have tracking issues.

It's a bit of a pickle

[Steve Davis]

PM sent.

Steve

[fenbach]

Radioroslyn said
"I doubt you would be able to get an osc coil design for a 455kc IF to tune down low enough to use it at 260kc."

How does the design of a 455kc coil differ from a 260kc coil? And, how would I determine the frequency range of an IF coil/Xfer?
thanks.