Orange AD200 MK3 Bias Ajust

[andbro]

Hi,

Do you how to adjust the bias on the Orange AD200 MK3?

See schematics


Thank

[pompeiisneaks]

That schematic shows a bias potentiometer. This would be used to adjust it. OTOH I don't see 1ohm cathode resistors, so you'd need to use the transformer shunt measurement method or get a set of bias probes for the power tubes...

~Phil

[jabguit]

/\ /\ /\

what Phil said. it is marked P1 (47K pot) on the PS schematic.


cheers,

[andbro]

Hi,

I have found the schematic from Orange. It's not very clear, but we can see the resistor 1 ohm.

The best tool is Probe Tester 8 Pin Socket Plate current or Tester 8 Pin Socket Cathode current ?

I have KT88 Vacuum Tube:
Power plate: 42 W

Ibias = (Power Plate * 0.7) / Vplate Is it Ok ?

But when you have only one potentiometer Bias ajust, how to proceed ?

Thank

[sluckey]

But when you have only one potentiometer Bias ajust, how to proceed ?

I adjust the bias pot to set the highest current tube to 70% and just accept the other tubes as they are.

[andbro]

Hi,

The best tool is Probe Tester 8 Pin Socket Plate current or Tester 8 Pin Socket Cathode current ?

Thank

[sluckey]

The best tool is Probe Tester 8 Pin Socket Plate current or Tester 8 Pin Socket Cathode current ?

You don't need any special testers. Simply measure the millivolts at TP8, TP9, TP10, and TP11. These voltages represent the cathode current for the four tubes. Then measure the plate voltage for each tube and do the math.

[pompeiisneaks]

Yeah that schematic is quite different than the one I saw, so it does look like you've got the 1 ohm cathode resistors you can use to measure current, per what sluckey just said.

~Phil