[ICOM] ICOM 746PRO local image problem

[Gregory W. Moore]

GM, Pat, es all the group members,

First, thanks much for your expert assistance... I was able tho, since I 
hadn't recieved ur msg yet, to fix the problem (boy, do I feel stupid 
--hi--)

I had decided that since the 746PRO was above my maintainance capability 
level, being an ole hollow state guy, being retired, and not having 
access to some of the specialized equipment of which I used to have 
access, the best move would be to simply suck it up, admit defeat, and 
send the unit to ICOM for service.  Soooo I called the repair center, 
and within 30 seconds, had the solution.  I had the xtal calibrator 
turned on, by some totally unknown reason.  I went into the menu, turned 
the thing off, and the birdies vanished.

I knew, after a huge troubleshooting effort, that the birdies were at 
even intervals, were binary multiples of eachother, and for some reason
were producing audio at 600Hz multiples, which made me think of the CW 
sidetone osc.  I also noticed that the "SCP" display showed regular 
signals at intervals.  I wasn't even considering the calibrator, because 
I had no need to use the feature, since I have the high stability xtal 
osc which I installed, and was, using 3 separate frequency 
counters/generators, dead on freq.

I simply can't believe that going to the menu and shutting the osc off 
fixed the problem. I have good power out now, and the sensitivity is 
right back where it should be. This leaves me with the realization that 
reading the manual should have been my original point of departure.  I 
also performed the factory reset as well, so as regards to the actual 
fix of the problem, well, your guess is as good as mine.  It is, 
however, working, and will give me a chance to put my channelized freqs 
(mainly N-MC MARS) in good order...

Again tnx much for your timely assistance

73 de Greg "GW" Moore WA3IVX/NNN0BVN



wa4tuk wrote:
> My IC-746 (not pro) developed strong birdies at regular intervals. This 
> was noticed just after turn-on.  I was so surprised I tried to receive 
> these with another receiver only to finally determine they were all 
> internal to the 746.
> 
> I really thought this was the end of the unit with the synthesizer or 
> CPU or something needing a level of repair not likely by myself.
> 
> A power cycle made no difference but a complete factory reset fixed the 
> problem to my great relief.
> 
> Page 81 in the 746 book. I don't know the exact procedure for the 746pro.
> 
> For the 746..."While pushing in [F-INP] and [M-CL], push [POWER]    to 
> turn power ON."   quoted from the IC-746 FAQ
> 
> Let us know if this helps.
> 
> Pat
> wa4tuk
> 
> 
> 
> Gregory W. Moore wrote:
> 
>> GE, All,
>> I own an Icom 746PRO, and it seems to have developed an annoying 
>> problem (S??) with the synthesizer.
>>
>> I have CW image freqs currently on 6800.0, and multiples of the same
>> as well as both 23 and 32 MHz and fractional harmonics of the same.
>> (6.800USB happens to be a SHARES nite PACTOR BBS freq.
>>
>> There seems to be a 600Hz multiple on an audio spectrogram, peaking on 
>> the selected freq, as well as decreasing harmonics every 600Hz up and 
>> down the freq scale.
>>
>> I also seem to have lost a great deal of selectivity/sensitivity in 
>> the front end, and tuning seems to pose a problem. There seems to be a
>> "hangup" in tx/rx switching, especially in digital modes such as 
>> PACTOR, when audio goes from normal to distorted going thru several TX/RX
>> cycles.
>>
>> These carriers seem to be "digital hash" and are indeed, binary 
>> multiples of eachother...
>>
>> Anyone in the group has had this problem?? any solutions, and possibly 
>> an  "at QTH" repair before I ship the whole shebang to ICOM for 
>> evaluation and service.....
>>
>> OPNOTE: This is NOT the CW sidetone, however, the CW sidetone is 
>> significantly diminished at these particular freqs.  I have chosen
>> the few I mentioned as a starting point, however, I have no doubt that 
>> other image freqs exist as well, and have to originate in the rig 
>> since it makes no difference if the antenna is terminated in a 75 ohm 
>> load or simply disconnected.  There is also static!! on the 2M band, 
>> which absolutely shouldn't exist...
>>
>> I have been driving myself nuts for a while with this problem,
>> the xcvr isn't that old, around 1993 vintage, and has apparently 
>> developed this problem only recently..
>>
>> 73 de Greg "GW" Moore WA3IVX/NNN0BVN
> 
> 
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