[AMRadio] My 51J4 didn't receive


Jim Tonne Tonne at Comcast.Net
Fri Apr 5 19:05:41 EDT 2013


Every now and then I come to my senses and decide I really ought
to take the hint that several guys have given me, and get back on
the air on 75 and 40 meters.

I have been listening to a lot of CW on the inter-net-tunable radio
in Amsterdam (someone sent me the URL) and I think my code speed is
actually getting back to where it was when I was in school.

Yep, gotta get on the air.   First step:  see what's happening on 75
and 40 here.

Next step is to turn on the radio, my Collins 51J4.
Radio put out white noise like it should until I attached the antenna.
But when I attached the antenna NOTHING happened.   No clicks,
no pops, no radio stations.  I cleaned the coax connector center
pin (been bit by this before when it was left outside and got
corroded).

The 100 kc calibrator worked OK so I knew the various oscillators
and mixers were functioning.   Just nothing from the antenna.  The
symptoms seemed to point to a dead RF amplifier tube.

I got the manual and was relieved to see that I had long ato written
down the various voltages on each tube pin as seen by my old
Simpson 260.   So I could see if, for example, the RF amplifier had
a shorted screen bypass capacitor or if it had cathode current.

Couple of days passed while I did productive things and fumed a
bit.

Just now I got out the Simpson 260, the manual and the receiver all
together on a bench.  Took off the bottom cover and the top cover.
Connected the antenna.   Turned on the radio and it worked like
it always did.  Yep, picked up lots of line noise (curse you, TVA)
and I could hear AM and SSB on 75, CW on 40.   Just like old times.

So I listened a while and yep got the itch to get on the air.

Just like old times.

While listening I put the top cover back on (removed it so I could
see if the RF amplifier tube had in fact a working filament).

I put the bottom cover back on.

Turned the radio around and noticed I had connected the antenna
to the antenna coax connector  (like you are supposed to).

Strange, I thought.  When it was NOT working I used the OTHER
coax connector.   The one marked "500 kc I.F. Output."

It seems that if you connect your receiving antenna to the I.F. output
connector of a receiver instead of the antenna input connector, the
radio might not work very well.  Yep, that's my final diagnosis.

- JimT   W4ENE






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