[Milsurplus] Tough cookie

[CL in NC]

My work on a B17F project leads me to seek out info not readily available online, so I use aviation museum archives, and look for books that may contain one scrap of esoteric data.  I bought a book from ABE Books on service and instructions for B24D radio equipment.  In it, it tells you how to calibrate or reset a BC375D to it's TU's after replacing the master oscillator tube.  On the D model is a control right above the name plate on the front.  You tune up the rig to CW power on the highest frequency of the highest frequency TU available, 'lock' the key down for 25 to 30 minutes, and then adjust this control to zero beat the transmitter using a freq. meter.  I guess when 
VT4-C's were a dime a dozen, keying your BC375 for 30 minutes at full power was not a concern.

Charlie, W4MEC in NC