[ICOM] Icom 751A Questions...

[Gary P. Fiber]

Eddy,

I would be more inclined to suspect a BFO trimmer cap, crystal padder 
cap etc  CW mode over the ram unit..
I don't have at hand which BFO controls CW but think its different than USB
Would not hurt to check the LPL and PLL alignment it only takes a 
voltmeter.
Just see if both are normal before you trim it up. Also the calibrator. 
I think you set that for 9:00 and adjust a coil for 3 volts but one had 
better check that in the service manual. If you have a freq counter to 
check after its all the better or trim the rig for zero beat with WWV or 
CHU though you may not be able to transmit on CHU's frequencies.
The memory board causes things like funny frequencies on the display 
when in trouble.
You can take out the ram unit, don't short out the battery, and look 
with a magnifier to see if there are any cracked solder joints 
especially on the ram unit connectors..
 If so touch them up nothing to loose except programming if you short 
out the battery. I no longer remember what the symptoms were when that 
happened but we did see that a few times. Icom Canada can reprogram the 
ram unit or grab an after market one from Piexx or Scott Malcom retails 
the one from Italy I think. Either are supposed to work fine.
I can say during my time at Icom America the most trouble we saw with 
the ram board was when an owner tried to renew the battery.

Here is something that may be related from Icom America's web page.


      Knowledge Base Article 5BA9554454

Issue
No TX output at all in RTTY or CW modes from my 751/751A. SSB and AM are OK.

Resolution
There is a bad carrier generator crystal on the main unit. Replace X1 
crystal.

Category
Amateur : HF : 751


Gary K8IZ






Edward Swynar wrote:
> Good Day All,
>
> I am the owner of an Icom 751A transceiver (serial #04386), which I
> purchased brand new in 1989. I have a question about the CW offset / memory
> board inside this rig, that I hope someone may be able to assist me with,
> from past experience...
>
> Specifically, all of a sudden---and on CW only---the transceiver's output
> signal is 2-KHz lower in frequency than the displayed frequency. I noticed
> this the other day when I called CQ: all of the stations responding were
> some 2.4-KHz below my displayed frequency, and I could work them only by
> activating my RIT.
>
> If I wish to answer another station's CQ, I must first set the station's
> frequency into BOTH of the rig's VFOs, then offset the transmitting VFO by
> some 2.4-KHz, and operate "split".
>
> This does not happen on either AM, or SSB---CW only (naturally, because it's
> my favourite mode!).
>
> The rig certainly IS useable this way, but I do NOT like it---I prefer to
> use just the one VFO for both receiving and transmitting, just as it
> "...used to be."
>
> I've been told by one seasoned veteran in such matters that the memory board
> inside the 751A (the circuit with the lithium memory battery) is the
> culprit, and should be replaced. Is this always the case...? Have others
> ever experienced this same condition, and if so, was the "fix" a replacement
> memory board...?
> Finally, are replacement after-market memory boards even available for so
> old a rig...?
>
> Any & all information is welcomed and appreciated. Thanks in advance, & my
> vy
>
> ~73~ de Eddy VE3CUI - VE3XZ
>
>
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