[Milsurplus] ARR-41

[Mike Morrow]

Bill wrote:

>I described the ARR-41 I owned in 1984/5. Mine had a
>production/factory AC supply. The stuff stamped on the chassis
>corresponded to the components mounted on the chassis. It literally
>looked like all the other modules. Sorry, no photos...

Hi Bill,

That's interesting and not too surprising.  There's always some exceptions.  However, the standard R-648/ARR-41 does NOT support the substitution of an internal AC supply without chassis wiring modification and additions that aren't present in any AN/ARR-41 document that I've ever seen.

(1)  The front panel power connector J301 has three unused pins, two of which *could* be used to supply AC to an internal supply.  But none of them connect to internal power supply chassis connector J202.  They don't connect to anything.  There are only two connections through the chassis wiring harness from the front panel to the connector for the power supply module:  (a) Ground, and (b) Switched 28 vdc.

(2)  The 28 vdc input power lead going from power connector J301 through power switch S304 to power supply connector J202 also connects 28vdc to every other module that needs 28 vdc, so all that would have to be separated.  The 28vdc filter cap at J301 would have to be removed (working voltage rating too low, and DC rated).  The AC line, if switched by S304, would only switch one side of the AC line.

It would be easy to backfit an AC power supply into a modified AN/ARR-41, but one can NOT take a standard R-648, pull the dynamotor power supply, plug in an AC replacement, and make it work from AC connected to J301.  The existing chassis wiring just does not support that.

I'm comfortable with my NO to the question of an AC-powered version of the R-648.  If any of the internal wiring had to be altered, and such modifications aren't documented in the military technical manuals or engineering change notices for the standard equipment bearing the R-648/ARR-41 nomenclature, then it really is no longer an R-648.

I would wonder what might motivate such a modification of the R-648 by the military.  I can't think of anything.  The only military applications I've ever come across for the R-648/ARR-41 was the primary purpose as the auxilary receiver to the AN/ARC-38 and -38A, and occasionally as a companion to the later AN/ARC-94 (Collins 618S-2) in aircraft that earlier had the AN/ARC-38/38A and AN/ARR-41 installation.  

My money ($0.02) still says the unit you had was likely AC-modified after its release from military service, or on the outside, was a specially-configured unit that didn't (and couldn't) serve in a standard R-648 application.  I believe that the R-105/ARR-15 had a Collins commercial version known as the 51H.  Maybe there was a commercial version of the R-648/ARR-41.  Any Collins commercial aviation products experts on board?

73,
Mike / KK5F