[R-390] R392 SS Audio

[Bill Cotter]

Another alternative attached.

73 Bill N4LG




At 01:10 PM 12/10/2016, Drew P. via R-390 wrote:
>Charles wrote:
>
>"Finally, for reference purposes [only -- do NOT build one of 
>these...],
>here is documentation on the factory "transistorized amplifier module"
>
>The modification using 2 bipolar transistors to replace the 26A7 
>audio output tube is GUARANTEED not to work correctly. It would 
>have large amounts of crossover distortion due to no forward 
>bias.  It may appear that the two 10k resistors to the 
>transistors' bases would supply such bias, but the center tap of 
>the transformer which feeds the bases is grounded and so would 
>shunt the bias to ground.  One could unground the center tap and 
>feed in the bias there (along with adding a bypass cap), 
>eliminating the two 10k base resistors, or better yet, just build 
>the MOSFET version which Charles recommends.
>
>Drew
>
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