09-14-2020, 12:23 PM
I managed time to work on this radio yesterday. The main board for the PLL oscillator section had to be moved to extract the old antenna connection assembly and replace it with the new part. With the two connector units side-by-side, it was evident that not only was the Hi-Z antenna transformer missing, but also the static protection diode. Somehow, this board missed part of the assembly line!
With the substitute board in place, all the antenna connections worked as advertised, presumably for the first time since this radio left the factory ~ 30 years ago. After this check, I went back to focus on the off-center filtering in the 455 kHz IF. Another pass through the alignment of this section seems to have improved the response, but it is a subtle effect, so will require more testing. I did find that my stock of parts has a possible replacement for the wide (6 kHz) ceramic filter if needed. I hope this won't be the case, as removing the circuit board is quite involved.
Ed
With the substitute board in place, all the antenna connections worked as advertised, presumably for the first time since this radio left the factory ~ 30 years ago. After this check, I went back to focus on the off-center filtering in the 455 kHz IF. Another pass through the alignment of this section seems to have improved the response, but it is a subtle effect, so will require more testing. I did find that my stock of parts has a possible replacement for the wide (6 kHz) ceramic filter if needed. I hope this won't be the case, as removing the circuit board is quite involved.
Ed
I don't hold with furniture that talks.
