K4040 v8 bias

can someone please give some advise on two problems on the k4040.
the first snag is why cant i set the bias on v8, the led does not respond to any setting, all other valve bias are settable. ive swopped over the valves ,but to no avail. all voltages seem ok. the rv8 voltage does vary at the junctions of r57 and r34.but the bias at pin 8and 1 can be seen,but no led’s light.when switch 4 is on.

the second concern is on v6, after about 1 min, the whole valve glows brightly. the bias was correct.???

We suspect some assembly problems.
Is the bias at the base of valve V8 correct when measured with a multimeter?
If this is the case, check the path to the readout for continuity problems.
V6: for some reason this valve is not receiving correct bias or the bias is intermittent.
Check with a multimeter.
CAUTION: The voltages in this amp can kill! The safest way to measure on a live amp is to keep one hand in your pocket at all times.
Please note that high voltages can remain present even when the amp is turned off.