Hi.

I suspect that the capacitor for the 10.7 MHz filter on one of IF can
of my SX-42 is shot. I've been reading about the problem with the
silver mica caps on IF cans here but I don't know whether the SX-42
has these caps in the IF cans.

This is my first major boatanchor restoration and I already replaced
all paper wax caps and electrolytics and checked all tubes. LO works
fine on both frequencies. AM works great but the FM is dead (or
anything on the 2 upper bands that use the 10.7MHz IF filters. I can't
pass a 10.7MHz modulated signal through the 2nd IF stage. An
interesting thing I noticed is that when I inject a 455KHz through the
2nd IF stage and switch the band to the upper 2 (FM bands) the signal
gets stronger.

Question: is there a way to disassemble the IF can in the chassis or I
have to remove it? How do I disassemble it?

Also, what is the value for the capacitor on the 10.7MHz part of the
IF can?

Thanks for the help.
--
Elias

I would remove the coil. Just make a diagram of the color codes etc.

Once you remove the can from the chassis it will be obvious how to
disassemble it.

The reality is that the cap is probably OK but that the coil is open. You
may find that a connection to the coil on the form may have corroded. I have
in the past been able to repair an open IF can by finding this open
connection and then unwinding one turn and reconnecting to the terminal

Good Luck


"Mazur" wrote in message
om...
Hi.

I suspect that the capacitor for the 10.7 MHz filter on one of IF can
of my SX-42 is shot. I've been reading about the problem with the
silver mica caps on IF cans here but I don't know whether the SX-42
has these caps in the IF cans.

This is my first major boatanchor restoration and I already replaced
all paper wax caps and electrolytics and checked all tubes. LO works
fine on both frequencies. AM works great but the FM is dead (or
anything on the 2 upper bands that use the 10.7MHz IF filters. I can't
pass a 10.7MHz modulated signal through the 2nd IF stage. An
interesting thing I noticed is that when I inject a 455KHz through the
2nd IF stage and switch the band to the upper 2 (FM bands) the signal
gets stronger.

Question: is there a way to disassemble the IF can in the chassis or I
have to remove it? How do I disassemble it?

Also, what is the value for the capacitor on the 10.7MHz part of the
IF can?

Thanks for the help.
--
Elias

I suspect that the capacitor for the 10.7 MHz filter on one of IF can
of my SX-42 is shot. I've been reading about the problem with the
silver mica caps on IF cans here but I don't know whether the SX-42
has these caps in the IF cans.

This is my first major boatanchor restoration and I already replaced
all paper wax caps and electrolytics and checked all tubes. LO works
fine on both frequencies. AM works great but the FM is dead (or
anything on the 2 upper bands that use the 10.7MHz IF filters. I can't
pass a 10.7MHz modulated signal through the 2nd IF stage. An
interesting thing I noticed is that when I inject a 455KHz through the
2nd IF stage and switch the band to the upper 2 (FM bands) the signal
gets stronger.

Question: is there a way to disassemble the IF can in the chassis or I
have to remove it? How do I disassemble it?

Also, what is the value for the capacitor on the 10.7MHz part of the
IF can?
=====================================

The IF coils in the SX-42 are slug tuned and have fixed mica
capacitors across each coil. The first IF Xformer uses a 27pF cap
across the primary and a 47 pF across the secondary, the second and
third IF Xformers use a 47 pF across both the primary and secondary
windings. These are the values for the 10.7 MHz IF coils. You will
probably have to remove the IF Xformer from the receiver to take it
apart. The increase in gain when you look at the 455 kHz IF amplifier
with the receiver switched to bands 5 and 6 is the result of the
difference in bias applied to the second IF stage on those bands. The
cathode resistor is decreased in value on the higher bands to increase
the gain. Your finding is normal.

E-mail me if you need more information.

Ed Engelken
Canyon Lake, TX