At Luke AFB 71-73 we had arc 3  as vhf tower backup... HA!  it backed up a  bc-640 at tx site and bc-639 at rx site vhf unites  one set for tower vhf the other  for vhf  guard.  although I already knew how  to work on the arc 3 stuff  it  was taken care of by avionocs sq.   all we did was pull the units out to swap them.
Ed Sharpe archivist for SMECC    former 30454  USAF
 
wish i had  the  640  tx  that was at  luke... Scot J  any idea who got that  drom DRMO?

In a message dated 10/10/2023 1:20:03 PM US Mountain Standard Time, milsurplus@mailman.qth.net writes:
 
Charlie
I was in the USAF from 67 to 72.  My training was in Ground Radio but if no other group on base had maintenance responsibility, Ground Radio got the task.  So we worked on the old ARC-3 and ARC-27 radios.  Both were in the MPN-13 RAPCON van when I was stationed at Mactan, AB, RPI.  There was also a GRC-32 at the control tower which is an ARC-27 and a big whopping power supply to produce the 27 VDC.
 
The MPN-13 was heavily air conditioned so both the ARC-3 and ARC-27 radios were pretty reliable.  The GRC-32 was run outside of it's case because of the heat.  IIRC it was used as a backup radio anyway and usually maintained by the Philippine Air Force.  There were also several TRC-68, aka GRA-53 or 54 type radios.  These are similar to the VRC-24 but have an AC line power supply in the same cabinet which also had a built in blower assembly.  
 
These radios really got hot during operation in the PI.  At times, they were so hot that one could not lift or carry the R/T unit back to the shop until they were out of the case for perhaps half an hour or so to cool down.
Fun times,
Jim
 
Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
 
 
On Tuesday, October 10, 2023 at 02:26:13 PM CDT, CL in NC via Milsurplus <milsurplus@mailman.qth.net> wrote:
 
 
I worked on the ARC 27 many years ago, and always wondered how well the plenum chamber cover transferred the heat from inside to outside.  They did get pretty warm inside that sealed box.  There was a little dinky fan inside the unit to circulate the hot air, with  a dual squirrel cage blower for the plenum on the outside.  There was one installation called the 'biscuit' because it was round and flat, that had a 27 out of its cabinet and installed in the open, along with several other pieces of gear, but the whole biscuit was in a pressurized compartment and designed to be a change out item to expedite air craft turnaround.  I have forgotten the aircraft it went in, perhaps an S2F.
 
Charlie, W4MEC in NC
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