[Milsurplus] URM-25D / J

[WA5CAB at cs.com]

Peter,

The nameplate on top of the case isn't a supplementary ID plate.  It 
identifies the signal generator set or equipment model, and all models of the 
AN/URM-25* have it.  The nameplate inside on the front of the signal generator panel 
itself ID's the model of signal generator used in that model or AN/URM-25.  It 
should read "SG-85C/URM-25D".  

There is a third nameplate on the power supply which should read 
"PP-977?/URM-25D".  If "?" is "A" then it is the same power supply used in the URM-25G and 
H.  If it is blank, then it is the same as used in the URM-25D (and if it 
reads "PP-562?/URM-25" then that's a different can of worms).  Which would give 
some sort of clue as to whether the SG-85C started life new as a "C" or was a 
modification of the oldest, the SG-85.

The SG-85/URM-25D was a significantly different design from the SG-44C/URM-25 
and got new nomenclature.  Just as the cheaper SG-103/URM-25F was different 
from the SG-85.  The signal generators used with the AN/URM-25G, H, and J are 
all modifictions, not new designs, of the SG-85.  I note that the "B" or "b" 
serial number prefix was also used on the AN/URM-25H and SG-85B/URM-25D but I 
don't know whether that means the SG-85C is a modified "B" or not.

In a message dated 9/7/2004 7:29:46 AM Central Daylight Time, 
jupeter at datafast.net.au writes: 
> Listers.. i just got a URM-25 D /J from Easy   Street. (USA)..   not
> only does it appear to be  as new and  complete with all slots in lid
> filled, but also has a  supplementary ID plate of the appropriate size
> screwed to the case topside showing the Serial # as B-9 and naming as
> a  URM-25 J.
> The small ID plate on  front panel says URM-25 D  . serial B-9 and
> mnfr # is 26648.
> Contract # is N00039-68-C-3586.
> Internally. there is a  professionally engineered /installed insulated
> plate mounted on  standoffs and placed just to the  side of the
> attenuator and  with a  couple of diodes IN570, filter caps etc.. The
> seller said the   unit had been factory modified to have it   conform
> to the  G model with the   zener regulator for osc.
> heater.-- --correct ?
> I haven't checked the   volts on it yet but it must be somewhat
> different from the   model G layout as the  xfmr is still the same
> with only the 6,3 V  heater winding as  distinct from the additional
> 12.6V on the G model

Robert Downs - Houston
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