09-29-2023, 04:05 PM
Generally IF transformers are somewhat generic in broadcast sets. The major considerations are impedance, frequency, bandwidth,
and physical size. The impedances between the input and output transformers are different. Going from the plate of the mixer to
the grid of the IF amp tube is going from a somewhat low impedance to a high impedance grid. The output transformer is a bit
different. It's matching and plate to the diode plate which is low impedance. I mention this because the the input vs the output
transformers do not make a good swap.
The frequency of the transformer needs to be tunable to the proper frequency. If by using the original tuning system or the
slugs/caps that are internal.
The bandwidth is mostly determined by the distance between the two winding in the transformer. For the bcb something around
8 to 10kc is a good width, for HiFi 15kc but on am there is no more HiFi.
Size can be whatever you can fit inside to old part and make it work.
Philco used 460kc IF transformers from '32-'36. I don't think that they have a high failure rate. The rf and ant coil do but IFT is an occasional problem on the sets I've worked on. They made a lot of those IFT's. I don't think it's a good idea to rewind it.
If you were desperate you could use a 455kc Ktran output IFT and retune it to 460kc.
and physical size. The impedances between the input and output transformers are different. Going from the plate of the mixer to
the grid of the IF amp tube is going from a somewhat low impedance to a high impedance grid. The output transformer is a bit
different. It's matching and plate to the diode plate which is low impedance. I mention this because the the input vs the output
transformers do not make a good swap.
The frequency of the transformer needs to be tunable to the proper frequency. If by using the original tuning system or the
slugs/caps that are internal.
The bandwidth is mostly determined by the distance between the two winding in the transformer. For the bcb something around
8 to 10kc is a good width, for HiFi 15kc but on am there is no more HiFi.
Size can be whatever you can fit inside to old part and make it work.
Philco used 460kc IF transformers from '32-'36. I don't think that they have a high failure rate. The rf and ant coil do but IFT is an occasional problem on the sets I've worked on. They made a lot of those IFT's. I don't think it's a good idea to rewind it.
If you were desperate you could use a 455kc Ktran output IFT and retune it to 460kc.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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