[ICOM] IC-735 misbehaves above 21.9 Mhz

[keith.miller5 at comcast.net]

Spoke with Matt Adrian in MI. He says that since my TX and RX are good it is not the VCO trimmer capacitors. He suggested maybe a PLL realign would be the place to start (which he will not do on such an old rig). Know anyone who still works on these rigs? 
  
Thanks. 
  
Keith 
KB0EMP 

----- Original Message -----

From: "D C _Mac_ Macdonald" <k2gkk at hotmail.com> 
To: "Icom Forum" <icom at mailman.qth.net> 
Sent: Thursday, October 29, 2015 8:05:58 PM 
Subject: Re: [ICOM] IC-735 misbehaves above 21.9 Mhz 

If I recall correctly, these trimmer capacitors had polystyrene dielectrics.  As they aged, they "outgassed" the plasticizer (like your auto dashboard) and this film then made the capacitors intermittent at first and then totally inoperative.  At one time, Icom procured some ceramic dielectric replacements that were far more stable.  I'm reasonably sure that Scott Malcolm and other Icom repair facilities can still fix that problem once and for all.  I'm also certain that Gary Fiber, K8IZ can confirm, expound, or refute my above statements. 
  
I still have the IC-735 that I bought new sometime prior to 1993! 
  
* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* (Since 30 Nov 53) * 
* k2gkk hotmail com * 
* Oklahoma City, OK * 
* USAF & FAA (Ret.) * 
* Icom User -- 1972 * 
* * * * * * * * * * * 
  
  
> From: gfiber at comcast.net 
> Date: Thu, 29 Oct 2015 15:45:34 -0700 
> To: icom at mailman.qth.net 
> Subject: Re: [ICOM] IC-735 misbehaves above 21.9 Mhz 
> 
> There are 4 screwdriver or tuning tool adjustable variable capacitors in the 735 VCO system. Each one controls a range of frequencies. They are set so a test point shows a DC voltage, possibly 3 volts on a certain frequency, that voltage will vary as the radio is tuned through the frequency range the particular VCO covers. If that voltage is not present the radio will not operate in a range of frequencies that VCO is designed to control. Hope this helps. 
> 
> Gary P. Fiber K8IZ 
> 
> 
> 
> > On Oct 29, 2015, at 2:54 PM, Nathan Moreschi via Icom <icom at mailman.qth.net> wrote: 
> > 
> > Trimmer caps? 
> > 
> > Sent from Yahoo Mail on Android 
> > 
> > From:"keith.miller5 at comcast.net" <keith.miller5 at comcast.net> 
> > Date:Thu, Oct 29, 2015 at 5:11 PM 
> > Subject:[ICOM] IC-735 misbehaves above 21.9 Mhz 
> > 
> > 
> > Hi, 
> >   
> > I have an IC-735. 
> > When I turn on the power to the rig, nothing is heard if the last frequency I was listening to was 22 Mhz or greater. 
> > As soon as I tune down to 21.999 or below, normal signals are heard and then I can hear normally anywhere on the bands until I turn off the rig. 
> > I can hear an audible relay click when tuning from 21.999 over to 22.000. 
> >   
> > Any suggestions? 
> >   
> > Keith 
> > KB0EMP 
> > ---- 
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> > ---- 
> > Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net 
> > Icom Users Net: Sundays, 1700Z, 14.316 MHz 
> > Icom FAQ: http://www.qsl.net/icom/ 
> > To support QSL/QTH.net: http://www.qsl.net/donate.html 
> ---- 
> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net 
> Icom Users Net: Sundays, 1700Z, 14.316 MHz 
> Icom FAQ: http://www.qsl.net/icom/ 
> To support QSL/QTH.net: http://www.qsl.net/donate.html 
                                                
---- 
Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net 
Icom Users Net: Sundays, 1700Z, 14.316 MHz 
Icom FAQ: http://www.qsl.net/icom/ 
To support QSL/QTH.net: http://www.qsl.net/donate.html