SAFETY FIRST! DANGEROUS VOLTAGES EXIST IN TRANSMITTER…REMOVE ALL POWER PRIOR TO REPAIRS AND USE GROUNDING ROD.

Question: Why does the screen overload light turn on with plate on?

Answer: Screen current overloads can be caused by shorts on the screen voltage line as well as a short on the plate voltage line.

Observe the screen current meter when plates are turned on and note if current goes full scale or goes negative.

If current goes full scale then there is a short on the screen circuit. Check for a shorted screen feedthrough capacitor or bent pins in the tube socket if recently replaced. Removing the tube for inspection may allow the pin to spring back in place so care should be taken during tube installation.

If the current goes negative then plate voltage is shorting to ground. In the 816R the screen grid is at ground, thus allowing the screen overload to activate first when plate voltage is shorting to ground. Possible causes of shorts are a shorted plate blocker, shorts at interlock assemblies, or a failed C52, a capacitor located in the exhaust tube near the top. Also, HV wire should be inspected for any worn areas such as worn grommets that HV wire passes through.