[Hallicrafters] Hallicrafters HT-45 MKII Amplifier

[Robert Davis]

I recently purchased an HT-45 MKII amplifier to match my HT-44 and SX-117.
   
  Upon close examination, I discovered that it has been modified for internal RF switiching, apparently so that it may be used with a transceiver.
   
  My attempts to "reverse engineer" the modification reveals that there is a 12-volt DPDT relay used for the RF switching to direct RF input into the amplifier circuit during transmit operation and to bypass it during receive operation.  
   
  Checking the continuity of the relay contact, it appears that there is no continuity between the input and output antenna connectors when the relay is de-energized. One would expect that there would be continuity when de-energized so that a transceiver can receive signals.
   
  My question is the following:  I suspect that this may have been a common modification to the HT-45. If so, there should be some articles, or technical data on the modification.
   
  1)  Does anyone have any information or source of information to learn more about this modification?
   
  2)  If the relay is defective, can anyone recommend a parts source?
  Any and all good information will be appreciated,.
   
  Thanks all.