[ICOM] IC-765 question

[Gary Fiber]

Look here http://www.ab4oj.com/icom/ps35/main.html

Grab the PS-35 user manual  PDF. IC1 and R5 used to be problematic in those
supplies too. R5 might have changed value, it is a current limiting
resistor. IC1 would not fire off all the time as I remember. If you look
through this manual and see the voltage change on the PCB layout, that is my
hand writing hahaha. Funny to me to see my hand writing all over the net.

Others here are more familiar with this supply than I am anymore, left Icom
in 2001 so daily tech support is history.  When I was there 80 telephone
support calls a day on all of their products combined was normal. My ear was
tired at the days end ;)

Gary K8IZ




-----Original Message-----
From: Icom [mailto:icom-bounces at mailman.qth.net] On Behalf Of Marc & Tricia
Niebergall
Sent: Saturday, April 25, 2015 7:48 AM
To: ICOM Reflector
Subject: Re: [ICOM] IC-765 question

Gary and Rich,

Thank you both for your input.  The fuse is cleanly soldered and power
output is normal. At this point while I have the board out, I plan to change
all the electrolytics as they are around 25 years old.  The freeze idea
sounds like another good troubleshooting technique and will give it a try.
The rig works marvelously; the only exception being this rather long pause
on first start-up.  Sometimes the pause is rather short, a 1/2 second or so.
Other times it may be as long as 2-3 seconds.  While 2-3 seconds doesn't
sound like a long time, it seems like an eternity when it happens.
I'm sure I will eventually find the cause.

Marc

On Fri, Apr 24, 2015 at 4:42 PM, Gary Fiber <gfiber at comcast.net> wrote:

> Marc,
>
> If you are lifting the main board in the power supply, look at the 
> bottom for a flat bar about 1/4 inch wide by about 1.5 inches long. 
> That is a current shunt resistor. Check the solder joints at each end 
> closely for cracks. If they are cracked, de-solder that resistor clean 
> up the solder and reinstall it using some flux and  fresh solder. DO 
> NOY flow solder past the holes in each end of the bar as doing so will 
> change it's resistance. What happens is if there are cracks in the 
> solder the 765 will work fine up to about 50 watts but will not output 
> any more power when it is increased as the resistor would heat up a 
> bit, the solder cracks would open and develop a high resistance 
> connection. This was a fairly common fault in that and the other Icom 
> supplies of this type like the ones in the IC-761 and IC-751 series. I 
> wished I remembered other power supply issues but there were not that 
> many with those switchers. One good thing though the DC plug coming 
> from the internal supply that plugs into the 765 is the very same 
> wiring as an external DC power cord for Icom HF equipment, verify 
> this,  I remember the techs running those radios on the bench using a 
> PS-30 bench supply many times when I worked at Icom America.
>
> Gary K8IZ
>
>
>
> -----Original Message-----
> From: Icom [mailto:icom-bounces at mailman.qth.net] On Behalf Of Marc & 
> Tricia Niebergall
> Sent: Thursday, April 23, 2015 9:08 AM
> To: ICOM Reflector
> Subject: Re: [ICOM] IC-765 question
>
> Rich,
> Thanks for another great idea.
>
> Marc
> On Apr 23, 2015 9:01 AM, "Rich Dailey" <redailey1 at gmail.com> wrote:
>
> > In lieu of a meter, you might try the following: Let the rig run for 
> > several hours, or a day, and see if the power cycles on and off 
> > without the delay. If it is normal, lightly freeze spray areas of 
> > the power supply while cycling power until the delay reoccurs. Then 
> > localize the spraying to individual caps, until you find the 
> > culprit(s). Sometimes requires heating the area back up with a blow
> dryer.
> >
> > Use to be the 'poor-man's' troubleshooting procedure, but not so 
> > much today, considering the prices I'm seeing for freeze spray -hi.
> >
> > Rich, N8UX
> >
> > On Wed, Apr 22, 2015 at 2:08 PM, Marc & Tricia Niebergall < 
> > mtniebs at gmail.com
> > > wrote:
> >
> > > When pushing the AC on switch there is sometimes a pause of a 
> > > couple seconds before the rig powers up.  Other times it comes on 
> > > almost instantly.  This usually occurs on the first application of the
day.
> > Don't
> > > know if it is a relay or an electrolytic capacitor taking time to 
> > > charge
> > or
> > > what.  I changed two 33uf electrolytics in the power supply that 
> > > were swollen, but no change.  Any suggestions are welcome.
> > >
> > > Thanks,
> > > Marc-k7wxk
> > > ----
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