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I have been studying the Service Manual for my TL922 in connection with the bias arrangements. On Page 6 it says "In ssb mode the zener diode is shorted by S3 lowering distortion"

Looking at the circuit diagram S3 only appears to change the HT supply at the transformer, lowering the voltage to the rectifiers for CW and from what I can see the 7.5 volt zener diode is in circuit for both modes. Looking at my amp that does appear to be how it is.

I thought the 3-500Z was a zero bias triode so just wondering how this all figures out?

Mike
VK2AMF.

Mike Fleetwood
Canberra Australia and Sidcup UK.

Worldwide email address is: mfleetwood@...

3-500’s are zero bias at low B+ once you get above 2500v you add bias accordingly.