"Mazur" wrote in message
om...
All,

I just finishing re-capping a Hallicrafters SX-42 I bought recently.
Thanks Phil for an excelent web site (http://antiqueradio.org/) and
big help. This is my first restoration of such complex communications
receiver. I did restore a Fisher KX-200 and X-202-B amps, a Sansui
320 receiver and a few smaller radios. The rig was in excelent
condition and after re-capping and cleaning up the contacts the AM and
shortwave bands worked great...

... but the FM is completely silent. When I move the band switch to
the upper 2 bands I can hear static in the AM reception and silence
when I switch to FM. Does this preclude any problem with the
bandswitch? I inspected the bandswitch and the wafers look very clean
and don't show any signs of carbonization.

Did you ever hear the FM working?

Does the second to top band work?. This is something like 27 to 60 Mc, if I
recall. There's usually some paging service noise or maybe a cab company
or something there This band also uses the 10.7 Mc IF section.

In the AM position, you say you can hear static. Do you hear any FM
stations in the FM band? The AM detector should detect FM stations, using
the frequency slope of the IF transformers.

It's very easy to test the radio's local oscillator. In the FM position,
the oscillator runs either 10.7 Mc above or below the signal frequency. It
could be either, and I forget which. Another FM radio can pick up the
oscillator signal. Tune the second radio to, say, 90 Mc. Tune the SX-42
around 79 and 101 Mc. Somewhere around one of those frequencies, you should
get what sounds like a dead carrier. If the top band oscillator section is
misaligned, the actual indicated frequencies could be different.

If your oscillator seems dead, a 7F8 which doesn't want to oscillate at FM
frequencies is a possibility, but I'm suspicious of locktal sockets and
pins, and a good cleaning might be in order.


I cleaned and inspected the reception switch as well and it seems OK.
All tubes check fine and voltages are as they should be.

I'll continue investigating the problem but any suggestions are
greatly appreciated.

Thanks.
--
Elias