[Milsurplus] URC-35

[paul alexander]

Joseph--

First, I need to remind you that my experience with this radio was 25+
years ago; my memory is a bit foggy!

Yes, the DC-DC converter is repairable, even more so if you have a
complete manual.  My suggestion is to start looking around the burned
area of the board, checking parts with an Ohmmeter.  I would also
check the two power transistors on the bottom of the converter module.
 I seem to remember much of the burned area had to do with a +20 Volt
supply.

The converter module is difficult (not impossible) to work on without
the extender cables.  If my memory is correct, there are test points
for most of the supply voltages on top of the DC-DC converter module.
Check those and see which one(s) is/are bad.  When you find one that
is bad, remove the cover from the module and tack solder wires onto
components in that area and use normal troubleshooting tecniques to
find the bad component(s).  As I recall, the troubles with this module
were not difficult to find, but, time-consuming, due to the difficult
access to the innards of the module while operating.

About the only advice I can give about making the repairs is to simply
replace the parts.  You may consider replacing them with larger parts,
if practical.  When I was in the Navy, I never really looked into
modifying the converter to be more reliable, as unauthorized mods
would get you in big trouble.  You may also consider running the
AM-3007 partially pulled out of the cabinet with a fan on top.
Remember to pull out the plunger on the interlock switch, if you do
that.

As for Eugene's comment about the WRC-1 supply not being suitable for
the URC-35, it would seem the WRC-1 supply should be able to replace
the one in the URC-35, but, that is not the case.  The URC-35 had a
different power distribution than the WRC-1.  It seems to me that in
the WRC-1, the R-1051 receiver supplied all its own power, while the
URC-35 DC-DC converter must supply power to both the transmitter and
receive circuits in the transceiver.  I do not know why the designers
of the WRC-1 and URC-35 did not talk to each other about this.

I wish I could be of more help, but, my memory is just not as good as
it should be.  Feel free to ask more questions, on or off list; I will
try to help as best I can.

Paul
wb9ipa


Message: 1
Date: Mon, 18 May 2009 15:57:13 -0400
From: Joseph Pinner <kc5ijd at bellsouth.net>
Subject: Re: [Milsurplus] URC-35?
To: Military Radio Radio <milsurplus at mailman.qth.net>
Message-ID: <54FE7F73-2CC4-454F-A095-867C553F53A3 at bellsouth.net>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed

Paul,

I have a URC-35B that I purchased from Jim Karlow a number of years ago.

I like it but I do agree with other comments that it does not put out
100 Watts.

Some time ago it ceased working and I did not get around to working
on it until this weekend. Sure enough, it has a bad DC to DC
converter module and the appropriate burned area (around a fried 2W
resistor) and a couple of 1 mf 150v caps that have failed.

Could you give me suggestions from your experience on anything I need
to do to make appropriate repairs. I do have a complete manual but I
know that experience beats the manual any day.

Joseph Pinner +
KC5IJd / NNN0PHR