I've finished building an SE 807 circuit with 6SJ& as driver. Can someone please explain why on one of the 807s cathode I'm reading 64 volts while on the other it is spot on at 21v (with 400 ohms as cathode bias)? Anode and screen voltages are the same as for the other valve (around 310v).
In my fault-finding trials I (a) swopped both output and driver valves and (b) isolated the problematic 807 from its driver stage but I still get the same high voltage reading on the cathode.
One other bizarre feature is that if I touch the grid leak resistor (1K) with the DVM probe there is a hefty spark on the output transformer!
I hope I can get some feedback which will lead me to solve this problem.
Thanks and regards to all.
Joe A
In my fault-finding trials I (a) swopped both output and driver valves and (b) isolated the problematic 807 from its driver stage but I still get the same high voltage reading on the cathode.
One other bizarre feature is that if I touch the grid leak resistor (1K) with the DVM probe there is a hefty spark on the output transformer!
I hope I can get some feedback which will lead me to solve this problem.
Thanks and regards to all.
Joe A