I found the schematic, actually the voltage across two series connected 12AX7 heaters wired for 12,6V operation must be 25,2V. I`d leave 15 Ohms resistor in place, but I`d change the series connected 5k6 resistor to about 2k2-2k7. This resistor with 15k resistor forms voltage divider, and "set" the bias voltage. I think that -24V is still on the "hot" side, you can measure the current through EL34s by installing 1 Ohm (or 10 Ohms) "sense" resistor between the cathode and ground on each EL34 (pin 8). By measuring the voltage drop you can calculate the current by Ohms Law (say, 60mV through 1-Ohm resistor is Ia+Ig2=60mA, and that`s about max. you can use with respect for max. Pa data).
Posting Rules
Members
Search
Help
Register
Login
Get a T-Shirt!
