[Kenwood] FYI FOR TS940 FET'S

[Clif Holland]

I did it to one radio. The difference was .1 Db SN. I had to realign the RX 
to get that. Just changing them caused a loss.

Clif Holland, KA5IPF
www.avvid.com


----- Original Message ----- 
From: "TIM MCGRAW" <w8btm at cinci.rr.com>
To: <Kenwood at mailman.qth.net>
Sent: Monday, October 04, 2004 5:43 AM
Subject: [Kenwood] FYI FOR TS940 FET'S


HAS ANY DONE THE FIX AND IS IT FOR REAL ???
> > > BEFORE I SEND MY 940 OFF I NEED TO KNOW
> > >  TNX W8BTM TIM
> > > http://www.guisard.com/
> > >
> > > recently, a Brazilian ham PY1NR found two factory assembly
> errors.
> > > Even the Service Manual, Revised Edition is wrong.
> > > There are two FET's soldered in the wrong position which affect
> > > directly the overall radio sensitivity and AGC performance.
> > > Probably, all TS-940 will have this problem.
> > > All details, description and pictures are available at
> >
> > I just tried it.  Well, as stated, I noted about a 10db gain in
> > receive sensitivity, and a lower noise floor.  However, I now have
> > some strange problem with mode control.  Radio sometimes has a mind
> > of it's own as far as what mode it's on.  I can be on LSB and then
> > for no reason it will switch to FM...Then I have to play with the
> > attenuator to get it to go back onto USB.  Or, I'll loose USB all
> > together until I turn it off, and turn it back on.  Other times the
> > VCO goes out of lock, and I get the infamous "dots" on the
> display.
> > So, I took it back apart, and resoldered pretty much every joint on
> > both boards.  Unfortunately, that hasn't cured the strangeness.
> > Next step I suppose is to go through the alignment procedures, and
> > cross my fingers.
> > I therefore suggest caution in doing the "correction", or mod. or
> > whatever you might call it.  These are 20 year old radios, and they
> > have a history of bad solder joints.  Seems as though any jostling
> of
> > the boards carries with it considerable risk of developing other
> > problems and intermittant conditions.  Bottom line is, if it ain't
> > broke, don't fix it. Or at least send it out to someone who's used
> to
> > tearing their hair out on a regular basis.
> >
> > Well, time to try that alignment.  It's Sunday, so I have the WHOLE
> > day, and may well need it!
> >
> > Kevin-  KC8GIA
>
> GOOD NEWS!! I came back, and for the heck of it, did a CPU reset-
> Now, all is fine!  I've been running it for the past couple of hours
> and no problems(yet~).
> As to the receive, it is certainly improved.  It may actually be
> better than my FT-1000MP!
>
> In any case, my notes above are still valid.  I don't think that I'll
> personally try another such improvement.  It's just too likely to be
> a major can of worms, and I can do without the headache.
>
> Good luck to those who go ahead with it!
>
> Kevin - KC8GIA
>
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