[ICOM] 751A Progress...!

[Edward Swynar]

Good Day All,

Well, I'm happy to say that I've made substantial progress in the repair of
my 751A transceiver here, i.e. fixing it up so that the actual transmitted
radio frequency on CW is the same as the frequency displayed on the dial
display...!

First, the bad news: I had to locate a dis-connected centre conductor in a
coax jumper (W104) on the main RF circuit board, & re-solder it. I was
obviously a tad ham-handed (no pun intended) when I had this board upside
down to work on it. And then I had to re-check the connections to the
optional 250-Hz low-frequency IF CW filter that suddenly---and
intermittently---decided to make the receiver "deaf".

The good news now: I swapped "X1"---the CW carrier generating crystal---with
a replacement from a spare board that I have here, & now the display
frequency matches the actual transmitted frequency on CW! And the rig
transmits & receives just as beautifully on SSB & AM as it did before...

And now the FINAL bad news (and, as always, suggestions are welcome): the
tranmitter only puts out 30-watts---maximum---on CW! (and yes, that's into a
52-ohm dummy load, too). The output is the prescribed 50-watts on AM, and
100-watts on SSB...but only 30-watts on CW...

The BFO offset frequency (via L33) is "textbook"...however, tweaking the two
trimmers that control RTTY offset DO impact the RF output wattage on CW. I
can actually reduce the output to near zero when I adjust just one of them!

I know I'm getting SO very close that I practically smell the scent of that
elusive success...but who would ever have imagined that the generating
crystal frequency could have changed all that much over time...? It
certainly does make one pause & wonder as to just how long these
transceivers were really meant to last...

~73~ de Eddy VE3CUI - VE3XZ