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