04-03-2024, 12:44 PM
Hi Ralph,
I'm looking at the Riders schematic and when the voltages seem out of whack as you describe, I look at the power supply wiring. First thing to check is the negative side of filter cap 56. It should not be connected to ground. If it is, then the negative bias voltages set up by candohm resistor 54 don't exist and unbiased tubes will produce funny voltages. So the point where 54, 56 and pwr transformer CT connect should be measuring around -12 to -20 volts to gnd.
BTW 6K6 should have 265v on the plate, not 175v, so the reading you have is normal.
I'm looking at the Riders schematic and when the voltages seem out of whack as you describe, I look at the power supply wiring. First thing to check is the negative side of filter cap 56. It should not be connected to ground. If it is, then the negative bias voltages set up by candohm resistor 54 don't exist and unbiased tubes will produce funny voltages. So the point where 54, 56 and pwr transformer CT connect should be measuring around -12 to -20 volts to gnd.
BTW 6K6 should have 265v on the plate, not 175v, so the reading you have is normal.
