10-23-2023, 07:51 PM
I've been picking away at this without making any headway. I've checked the continuity of each section of the antenna and oscillator coils, and tested connectivity to and through the band selector, and I've checked capacitor values. At this point I'd love to hear from someone who has a 41-255 operating correctly on the upper SW band. To help with diagnosing the problem, I marked up the antenna and oscillator sections of the schematic to show the band switch in the upper SW position. As far as I can tell, there's no antenna tracking when that band is selected - only the LO section of the variable capacitor seems to be in circuit and the antenna circuit is fixed. And I've continued testing the idea that the LO is supposed to be on the high side of carrier/dial frequency, and it just doesn't seem possible. The LO starts well below dial frequency with the oscillator compensator closed and at maximum capacitance. slowly backing the trimmer out moves the LO up in frequency in a linear way and easily places it 455 below dial frequency. But the trimmer has to be sloppily wide open for the LO to be 455 above dial frequency, and then it won't move proportionately to dial frequency at all.