[Milsurplus] URC-35

[John Kolb]

I've got a URC-35 also - receive works OK, but power shuts off when transmitter
is keyed, requiring power switch to be turned off, then back on.

Any hints for attacking this?

John
KK6IL

At 04:53 AM 5/20/2009, paul alexander wrote:
>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