MKIII Bias at 1.7v

Greetings. It's been ten years since I restored my MKIII's, and they have not seen much use since. I ordered sand installed some banana type plugs and did away with the old screw terminal strips. After wiring them in, one amp biases to .50v and the other is up around 1.7v on both output tubes.

The restore was done using "Roy's" boards; individual bias controls amongst other things. I'm not that experienced with these projects, and it's been some time since I did this as a hobby... so I am hoping someone can lend a hand. Thanks.

snip73 wrote:Greetings. It's been ten years since I restored my MKIII's, and they have not seen much use since. I ordered sand installed some banana type plugs and did away with the old screw terminal strips. After wiring them in, one amp biases to .50v and the other is up around 1.7v on both output tubes.

The restore was done using "Roy's" boards; individual bias controls amongst other things. I'm not that experienced with these projects, and it's been some time since I did this as a hobby... so I am hoping someone can lend a hand. Thanks.

As this are no dynaco MkIII ,schematics should be posted to have any accurate advices.

https://ibb.co/6tBHbnR
https://ibb.co/x2Cr8Zc


Thank you!

snip73 wrote:Greetings. It's been ten years since I restored my MKIII's, and they have not seen much use since. I ordered sand installed some banana type plugs and did away with the old screw terminal strips. After wiring them in, one amp biases to .50v and the other is up around 1.7v on both output tubes.

The restore was done using "Roy's" boards; individual bias controls amongst other things. I'm not that experienced with these projects, and it's been some time since I did this as a hobby... so I am hoping someone can lend a hand. Thanks.

looking at the published schematics :
measure the grid voltage ( bias) If it's normal ( compare with the other amp) then
there could be a problem with the cathode resistors or the ground connection(s)

The cathode resistors all measure @ 10K, so I will look into the ground issue. Thank you.

It was dirty potentiometers. Amateur mistake! Thank you for your help.