Please assist me bias a new to me ST-70!

I just bought a used factory built VTA ST-70; finally, finally!
It is the version with ECC81 driver tubes.
Unfortunately it didn't come with any documentation.
Now I try to bias the amp for el34 and 6P3S-E tubes.

I installed all tubes, connected amp to preamp and connected speakers to amp,
turned on the whole system and made sure no signals go the the amp.
Then I measure the bias of the front left tube by placing the black probe
on the chassis and the red probe in the 'Biasset 1.56v' hole
and adjust the adjuster until the reading is about .4 V.
For the back left tube I placed the red probe in the hole on the opposite side of the socket.
Then I did the same thing on the right side.
I did go back and check all reading. they are all about 04 V now.
The system was on from the beginning until I was 'done'.

I am not sure if it was the right way to bias this amp.

Oh, And if someone has a copy of the user manual please email me.
I would appreciate your helps. Thank you

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Thank you, Bob

Someone told me to install and bias only 2 left tubes first turn off amp.
Install 2 right tubes, turn on amp and bias the right tubes.
I did put all tubes in the amp turn it on and bias.
I hope it works this way too.

I tried to modify my email but it did not work.
Still the same but now .com instead of .net.

Again thank you Bob

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Your way, doing both channels at the same time, is probably better. You may notice that the adjustments interact; when you adjust one, the other channel shifts, as the load on the bias circuitry is causing its voltage to shift slightly. So once you adjust one channel, then the other, you should go back to the first one and check it, then readjust if necessary. Re-check the two channels back and forth.

I am wondering if it would be better to bias an amp with out a preamp plugged in?
This way no signals will ever get through the amp.

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Bob,
Can I replace the center 12at7 center tube with a 12au7?
Gin