[ICOM] 756Pro Tuner "mystery" solved, inconsistencies

[Tom Norris]

No, the adjustment menu remains a mystery as
does the inconsistency between manual and actual
menu, but I did find the problem.

Yes, the radio is out of warranty.

When physically inspecting the tuner board I found
2 relays that looked "swelled" - further investigation
proved them to be shorted - their contacts welded
together. Either mismatch or a lightning blip, and I
am afraid it could indeed be the latter - when initially
checking the relays/board, by using the inputs to
the 54562 ICs to drive the relays, I also found
an output on IC-2 that does not go "all the way high"
and does not *always* activate RL-6. Easy enough to
replace chip and relays, perhaps socket the new ICs.

Photos of the dead relays --
http://www.fernblatt.net/mystery/756tuner/2relays.jpg
Note the melted hole in the foremost relay - which was
RL-11. RL-13 also had a deformed case, but no hole.

http://www.fernblatt.net/mystery/756tuner/friedRelay.jpg
Note the burned contacts of RL-11

Now, to the next inconsistency in the manual. *all* the
relays on the tuner board are marked with the part number
"NY-12W-K" as is the schematic. The parts list gives
relay 13 and 14 different part numbers The commercial
pn of these according to the manual are "AG 2011344"
with the Icom part being 6330001330 versus xxxxxx1510
for all the rest.

The good news is that while I had it apart I did a full
alignment check, and other than the S meter and one
more adjustment, it was fine. Very clean output even at
full power, looking at the spectrum analyzer.

I'd still like to know more about the "top secret" adjustment
menu, though.

73

Tom NU4G