[SignalOne] Driver Transistors

[EDWARD SCHUMACHER]

Hello and Happy New Year to All,

I have finally been able to get back on my CX-7 after many months and can report that the radio is actually in better shape than I first thought. Have also already found a couple of the problems and will be working on those today. It appears that possibly both of the driver transistors have given up the ghost also so I am looking for anyone who may have a couple of spares they would be willing to part with. Q4 is definitely gone as the bias resistors have been running hot tho still check ok for value. Q3 is also doubtful but I figure if I am replacing one I may do both unless an out of circuit check shows it still good.

During troubleshooting of the display which had gone out yet again, I found an intermittant which restored the display and suddenly realized the entire receiver had come back to life! I may be close to solving the low receive problem soon and then will only have the transmitter output to resolve. I think the driver transistor may have been going out all along and the NOS final may have finished it off. I have info that the 8072 was, among other faults, prone to going gassy on the shelf and would flash after warming up. We all know what that means in a CX-7.

I have not contacted RF Parts yet, one of my go to sources for old stuff, but am hoping to find either the TRW PT3657 or Mot 2N5641. Maybe with the drivers repaired the original final may have better output but I am still cooking the NOS tube and hoping to salvage it.

73 ... Ed, WA9GQK