While repairing an old radio with no AM reception, I found on my multimeter that there is continuity between the primary and secondary windings of the first 455 kHz IF transformer in the circuit. I desoldered it and found that the windings are still reading 0.6 ohms between primary and secondary. Is this normal? I checked for shorts between the can and IFT coil but there are none so I am not sure why the windings would appear to be connected.
It's not normal to have shorted coils when they ought to be only magnetically coupled by the helical tuning slug and resonate with the fixed cap to get the centre frequency at 455kHz with a bandwidth of about 15kHz.
If you can rewind ok. if not this may work http://www.rf-microwave.com/en/shop/0/211-455-khz-55-mhz-107-mhz-if-coils-transformers/2531-B-455-E-10-R.html
Or better review these specs http://www.mouser.com/catalog/specsheets/XC-600131.pdf
Always use a plastic or wood driver for the ferrite slug and very gently.
Depends on the radio. I would need more detailed info about the radio (make & model # ), but the first IF stage is your mixer/oscillator and most of the time it is a tapped inductor (that looks like the other if transformers). Later on in the integrated am/fm stereo receivers they were relocated to an external ferrite antenna stick to minimize interference with the other circuits.