"ablebravo" wrote in message
ups.com...
thx richard. esp on how to test the coils. i will do
that before
checking the IF again. i am suspecting the IF because a
couple of the
adjustments were near the travel limit, which may mean i
am in wrong
place. where it works, it's hot.

i was pretty sure on the tuning gang -- could adjust the
vanes and get
the crackle to change and nearly disappear. i flushed it
good, blew it
out and cleaned and cleaned. after spending hours on it,
i bought the
part. i think something might have been in the bearings.
in the
'crackle spot' the signal died and set could not be
aligned. it
blotted out some of the align freqs. no such prob
w/replacement part.

ab

Do you have a signal generator of some sort? I thought
from your posts that you do. You really do need one to set
up the IF amplifiers. It should be capable of putting out
455 khz preferably with some modulation. The usual
requirement is for 400hz at about 30%. The modulation level
is not critical but most signal generators are not capable
of high modulation level.
Its also helpful to have a crystal calibrator, preferably
one which puts out fairly low frequency markers in addition
to higher frequency ones. 10khz is nice to have. Mine has
100khz, 1.0 mhz, and 10mhz. This can be used directly to
calibrate the receiver and also to calibrate the signal
generator. If you don't have these tools perhaps you can
borrow them.
If the IF transformers are near the limit of their
adjustment, and you know the test frequency is correct, its
probable the resonating capacitors have drifted in value. I
believe this receiver uses permeablility tuned IF coils
(asjustable dust cores).
Again, since the problem seems to be isolated to two
bands and at least one band works OK I think the IF is not
at fault, or at least not the main cause of trouble. I
suggest checking the wiring of the tuning capacitor again to
make sure its OK. You might want to check the other
capacitors in the oscillator and RF stage. I am suspicious
of the oscillator because you say it quits near the low end
of one band. That sound to me like a bad coupling capacitor
there. If you have access to a good RF voltmeter or
reasonably wide band oscilloscope you can check the output
of the oscillator. Even a pick-up loop will show if the
output is varying a lot or if the LO is quitting at the low
end of a band.
Just some things to look for. Remember, this RX is more
than fifty years old so it may have a lot of tired parts (so
do I).


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Richard Knoppow
Los Angeles, CA, USA