[ARC5] PRC-77 Surprise

[Robert Eleazer]

I have a PRC-77 with a dead 5.6 MHZ IF module.  I took a look at it to see if I could figure out what is wrong and had a surprise.

It seems the earlier design of the module, used in the PRC-25 and presumably early model PRC-77's, used PNP transistors.  The later version used NPN transistors, 2N918's.  The two different module designs are interchangeable and the circuits are essentially identical, even to parts placement, except for how the two transistors are connected, emitters either to ground or to the B+ supply.

I have never thought of having two circuits that were the same but that used PNP versus NPN transistors.  And it led to some head scratching for me, too.  I thought my old Sylvania transistor substitute guide was wrong for while there.

Wayne
WB5WSB       
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