04-12-2020, 10:36 PM
Getting there. I spent a while today working out which trimmers operate on which bands, and have that charted out. This enabled setting the oscillator tracking on all three bands. One easy method I like is to use an accurate receiver and pick up the local oscillator. Set the dial of the radio being serviced to a round number, set the listening radio to this value +IF and tune the oscillator trimmer until it is received.
One thing is that although broadcast reception is strong, I feel that the SW bands are weak. The higher band in particular, and this one also has a problem that the set pops into instability/motorboating at the high frequency end of the dial. I looked at the resistors around the 6A8, and found the oscillator grid leak has drifted high, now 120k from 60k nominal. I'll be changing that and retesting.
The antenna circuits on this radio seem not too responsive to their trimmers. That may be worth a look, as perhaps something is amiss here as well.
Problems, yes, but I am rather enjoying them
One thing is that although broadcast reception is strong, I feel that the SW bands are weak. The higher band in particular, and this one also has a problem that the set pops into instability/motorboating at the high frequency end of the dial. I looked at the resistors around the 6A8, and found the oscillator grid leak has drifted high, now 120k from 60k nominal. I'll be changing that and retesting.
The antenna circuits on this radio seem not too responsive to their trimmers. That may be worth a look, as perhaps something is amiss here as well.
Problems, yes, but I am rather enjoying them
I don't hold with furniture that talks.
