Hello…
I have a big problem to my K8010… R65 - R66 - R70 - R71 is burning all the time after 1-2 hour after I change it the is same fault.
And I have all new tubs to K88? Bias is 3.6 v
What is bad??? 
I is wery 
on this K8010 I think this is poor…
This can have different causes and is hard to troubleshoot from a distance.
Use original tubes that came with the kit.
Make sure negative bias is present.