[ICOM] Icom 751A

[Jim Vohland]

From: Jim Vohland <n9vo at hotmail.com>
To: icom at mailman.qth.net
Subject: IC-751A
Sent: Tuesday, September 20, 2005 2:27 PM
All very interesting dialogue. I cant say a whole lot about the syntheiser 
noise comparasion as I havent noticed it being to bad. Partly I could 
attribute that to having mine gone over. After I originally purchased it, I 
sent it to Scott Malcolm and had the trimmer caps replaced and he repaired 
some bad joints on the pll board. It is working like new now. I also found a 
piexx ux14 board which solves the band stacking issue. The band stacking 
problem was my own personal dislike. With that board, the issue is gone. It 
also allows computer control of the rig if desired with a program like Ham 
radio deluxe. I probably will deal with the battery issue. Either a board or 
will install the dual battery mod. Either way that is a easy issue to fix.

It's a bit of an old rig, but I believe it's reputation as a great receiver 
is well earned. Glad to have it back in the shack.



Hi Jim,

Without entering into the "analogue vs. DSP debate":

I had an IC-751A from April 1990 until I sold it early in 1994 because it
was gathering dust on the shelf below an IC-781 which I was using
exclusively at that time. My 751A was fully-loaded, with FL-52A, PS-35,
CR-64 and speech board. It was even fitted with the RC-10 keypad. (The
IC-781 left my station in November 1998.) The 751A drove an IC-2KL/AT-500
pair for seamless, 500W auto-tune operation.

The SSB filtering and PBT operation on the 751A was far superior to that of
its predecessor in my shack, an IC-765 with the PBT mod. (I put that down to
FL-80/FL-44A vs. FL-30/FL-96). However, I did find that the 751A's PLL
synthesiser was somewhat noisy as compared to newer radios using a DDS
design (-104 dBc/Hz at 2 kHz offset, as compared to -111 for the IC-765 and
-125 for the IC-756Pro2). This led to relatively poor close-in reciprocal
noise mixing performance. I also found the lack of band-stacking (requiring
retuning in all cases when changing bands) rather cumberso



The RAM backup battery on the EX-314 RAM board never failed in my 751A, but
nowadays I would recommend replacement with an aftermarket ROM board such as
the Nardo or PIEXX product.

In the course of replacing the notorious HPL VCO trimmers, I found that the
paper-phenolic PCB material had a nasty tendency to de-laminate.
Fibreglass-epoxy board stock in more recent Icom models cured this problem.

http://www.qsl.net/ab4oj/icom/oldicom.html

I enjoyed my IC-751A in its time, but would not wish to acquire another one
at this point.

Cheers for now, 73,

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