"K7AAY" wrote in message
oups.com...
Given an SX-100. It doesn't work.

Chassis and interior in good shape, no corrosion. Lights
fire up when
turned on. Attached Hallicrafters 3.2 ohm speaker (or
headphones if
plugged in) hums, and I hear scratchy noises when I change
across the
bands or switch to phono. S-meter moves across the dial
when I spin the
sensitivity knob.

But, it doesn't actually receive anything, and the S-meter
does not
move as I traverse the bands nor does it change as I move
within a
band.

Suggestions on priorities for troubleshooting, by tube
replacement or
otherwise, appreciated. I feel the detector is the place
to start?
Have a multimeter, is all. In Portland (OR) Metro area.

0A2 voltage rectifier $6
5Y3GT rectifier $10
6AU6 1st mixer & crystal cal (1 ea) $10
6BA6 1650 KHz IF amp, 2nd mixer, 50.5KHz IF amp (1 ea)
$8
6BJ7 detector/AVC/noise limiter $5
6C4 1st conversion oscillator & KHz IF amp (1 ea) $13
6CB6 RF amp $5
6K6GT audio output $8
6SC7 audio amp/BFO $9
12AT7 2nd conversion oscillator $13

Your Elmering would be appreciated. Thank you in advance.

If you hear noise when changing the band switch try
cleaning the switch and the tuning capacitor contacts. Also,
blow out the tuning capacitor to make sure there is nothing
shorting the plates.
If you have not tested the tubes do so but I think a bad
tube is unlikely.
Do you have any service instruments (VOM, scope, etc.)?
Do you have the service manual? If not there may be a
free one on line somewhere. If you have the book you can
check voltages at the tube sockets, this will often find the
problem or give you a pretty good clue as to where it is.
Evidently, the power supply and audio stages are working.
If you have a signal generator try inserting a signal into
the IF strip. You can often do this by wrapping a few turns
of wire around a converter tube. The SX-100 is double
conversion so there are two I.F. frequencies, again, a
handbook will be very helpful.


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Richard Knoppow
Los Angeles, CA, USA