[Boatanchors] [Milsurplus] URM25

[Paul Kraemer]

No it is not a KISS refurb
I don't believe she did anything that would qualify as a mod in these unless 
you call replacing parts a mod.
I have been in a fair number of these myself and this is factory, one of two 
I have like it. The voltage across the zener  measures 5.9v suggesting to me 
it is some filament power
Paul K0UYA

-----Original Message----- 
From: rbethman
Sent: Sunday, October 12, 2014 2:22 PM
To: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] [Milsurplus] URM25

It sounds like the KISS Electronics refurbish of the AN/URM-25.

Just someone figured it out earlier.  KISS replaced the 6X4 with a
rectifier assembly and added the requisite capacitors.

They also did a fair bit of other mods while they still were
refurbishing them.

Bob - N0DGN


On 10/12/2014 3:10 PM, WA5CAB--- via Boatanchors wrote:
> Paul,
>
> AN/URM-25D was the first in a line that included AN/URM-25G, H, J & K.  J
> and K are rare.  The signal generator used is the SG-85, which went 
> through
> four modifications, basic through D.  If you look on the signal generator
> nameplate you should see a suffix letter after the 85, at least a "B".
> NAVSHIPS 0967-187-5010 with 7 changes and 2 temporary changes covers 
> AN/URM-25D, G
> and H.  I have never found anything on J or K except a short calibration
> instruction.  The power supply in AN/URM-25D is PP-977/URM-25D.  This 
> changes
> to PP-977A/URM-25G.  PP-977A has a 12 VAC winding and a regulator circuit 
> for
> the oscillator filament.  SG-85B is used in AN/URM-25H, and has the
> outboard circuit board you found.  The circuit is a voltage 
> double/regulator.  The
> manual and changes do not make it clear whether the power supply went back
> to PP-977, remained PP-977A either modified to remove the regulator or 
> with
> the regulator there but unused, or changed to PP-977B.  You might check 
> that
> out and report and I will add it to Change 7.  The added regulator circuit
> and some rewiring associated with it were added with Change 7, but they 
> did
> not add a modified complete schematic.
>
> One other comment - if the nameplate on your case still says AN/URM-25D 
> but
> the one on the signal generator says SG-85B/URM-25D or later, someone
> swapped case or generator.
>
> Robert Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
>
> n a message dated 10/12/2014 12:20:04 PM Central Daylight Time,
> elespe at lisco.com writes:
>> Got into a couple URM25D with an extra board mounted below the audio
>> section behind the rf attenuator.
>> Board has two power resistors, two electrolytics, two top hat diodes and 
>> a
>> stud mount diode.
>> I have not encountered this option before
>> Can anyone enlighten me what it is?  Guessing maybe dc filament supply
>> from size of components?
>> I don’t find it documented anyplace I have looked
>> Thanks
>> Paul K0UYA

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