Bias to high and blue glow at V5/V6 - A15mk1

We've just built two A15mk1's. One works great but the other one gives too high BIAS voltage (90mV), the voltage does not change at all when trying to trim VR9. The tubes always glow blue.
We double checked the wiring and can't find anything obvious.
If it helps in troubleshooting: we also found that the voltage after the rectifier was less then specified in the manual (V1.4). We measured approx. 210V instead of the specified 292V. Voltage at pin 8 and 9 on TR1 seems fine. The amps both work and sound good, but we're a bit worried that the high voltage and blue glow will affect durability of the tubes.

Grateful if you could point us in the right direction.
(You can answer in German if you like, we understand German quite well but don't speak that well)

Re: Bias to high and blue glow at V5/V6 - A15mk1

Thanks for your answers.
I've switched the tubes with the other amp and i've still the same problem.
I only don't understand this:

Zitat von MAD

What is the bias voltage (negative voltage at the grid) at the power tubes?

What do you mean with the grid?

Re: Bias to high and blue glow at V5/V6 - A15mk1

I measure +- 20mV with peaks to a high value (V). These values I can't measure cause my meter is too slow.

This value is -19V on the other amp, which works great.

Re: Bias to high and blue glow at V5/V6 - A15mk1

Thanks for your Help MAD, the problem is fixed.
There was a missing wire (from "-" of C26 to ground at the underside of the print).
Now the voltages are right and the bias voltage 35mV.