12V Safety and Control

My BIAS transformer was freshly replaced - in addition to the negative tube-bias voltage, this transformer also provides 12VAC for safety, and control. To ensure trouble-free operation in this 12V safety and control, I did not initally hook up the BIAS transformer's 12VAC secondary, but rather I selectively applied a current-limited bench-supply.

My test strategy:

• Use the bench-supply to inject 12V upwind of CR206, to verify wiring K203 through K101 Antenna Change-Over Relay, to the rear-panel T/R RCA-jack.
• Inject 12V downwind of CR209, and selectively bypass S205 Lower Door Safety Switch, and the 3-min timer K202, and see if pressing S203 "ON" switch will engage relay K203
• Inject 12V where the transformer will connect, bringing up all lights, allowing HV Relay to be enaged with front-panel "ON", and allowing the rear T/R jack to switch the antenna once the HV Relay has switched. The whole 12V enchilada :-)

• 

  Good! Injecting 12V onto CR206 anode allows K101 Antenna Change Over Relay to be controlled by the rear panel. Maximum current-draw is 0.31A with K101 and K205 engaged.

• 

  More Good! Injecting 12V onto C211b let me try the "ON" button, and watch K203 engage! Maximum current-draw with K203 engaged was 0.21A.