Posted to FB group Vintage Transistor Radios Oct 7 and after.
Yeah, it’s a bit confusing because the number of IF transformers is one more than the number of transistors.
When you work on IFs, what do you use for alignment? I got Zenith Royal 500s that the previous owner apparently fiddled with the IF cores. I guess I need a sweep generator.
Phillip Grace replied
Yes, a simple fixed frequency generator is all that is needed, along with a DMM to read the DC voltage at the detector that drives the AGC circuitry. You can also use a generator with AM modulation along with the DMM set to AC to measure the audio level, or a scope. A sweep gen can come in handy when tuning sets that have wide bandwidth IF stages, but not necessary.
Me: Thank you for the informative replies. I read some docs online about alignment of AM radios. I have done FM alignment with a sweep generator. One of the radios tuned in 640 kHz with the tuning cap set at 780, so I retuned the LO coil to get it back down to 640. Another one looks like the cores on the IF cans have been messed with, so I think that may be the problem. But many of these have a bad volume control, so I’m going to work on those to get the audio stages working. Just getting the battery holder contacts restored is gonna take a lot of time. So I have to do a lot of TLC that will take time.
