Route 66 bias.

[arfy]

Anyone out there familiar with adjusting the bias on a Dr. Z Route 66? I've done blackface Fenders, measuring voltage at pin 3 and current from the plate at pin 3 to the red OT center tap on the circuit board, but can't ID the center tap in the 66. And, I'm not really sure if this method applies to ulralinear output stages. Perry, or anyone?

[gregc]

ZAP!
OUCH!
gregc

[PerryR]

Hey Arfy,

You can measure the bias the same way. And I can tell you where the OT center tap wire is. The center tap of the output transformer is a red wire with a white stripe, its the only red wire with white stripe in the amp. Follow it from the output tranny to the large filter cap. where the red/white whire is soldered to the cap is an easy place to attach your probe.

As always, high voltage, be carefull!

[arfy]

I emailed the Dr. and he gave me the same answer as your post, I adjusted it last night, it was pulling .042 amps so I adjusted it down to .036, guess the Groove Tube HP's bias a little different than the stock Chinese ones did.