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Hi Leo, I swapped around the middle two tubes and the higher reading stayed with the tube so I think that one must just be a little out from the others. From what I've read 5-10mV between tubes is generally considered ok? Obviously the closer the better in terms of hum but generally speaking...

Update on this; I received a new matched quad of KT77s today and have just put them in and given the amp a good workout. So far there's no red plating in the troublesome tube position but I am a little perplexed by the bias readings; Starting from closest to the OT 1: 28.2 2: 30.9 3: 35.2 (the...

Yes I have been checking the readings with the master at 0 and no other jacks connected. To be honest at this point I feel like my only option is to buy more tubes and hope for the best, or at least rule them out. Both sets I have seem defective in some way so I can’t really reliably try and...

Hi Leo, I tried reducing the volume, when I turn the master down (to approx. 8 o'clock) the red plating tube actually got brighter, channel 2 level was at around 10 o'clock. I have checked those resistors, the 2k2 and 1R resistors checked out ok but the 220k was really hard to get a reading...

Thanks Leo, I have checked all the resistors around the faulty tube and all check out ok. I have also tried moving the tube and it is that position that is the problem as red plating occurs with any tube. I have also retensioned the pins in the troublesome socket but this unfortunately made no...

Hi Leo, it only red plates when playing. If I stop playing for a short while, the tube presumably cools down again as the red plating slowly fades

They're attached with flying leads

I'm really hoping that spending another £130 on a new quad isn't the only answer. I've read some other forums posts on one hot tube and most of the prevailing advice was that if it's done it once, it will do it again. What I can't make sense of is that the bias readings are all within normal, so...

Update on this, I replaced the 1k resistor but I am still seeing some noticeable red plating on the problem tube position when using channel 2 and only when I am actually playing, is this normal? Not quite sure why just this position would be affected if it was a bias issue so would seem to...

Ok awesome I'll give that a try, thanks for the response!

Hi, New forum user here, wondering if anyone may be able to help with some biasing strangeness that seems to be happening with my VH-2. My set up is amp -> Suhr Reactive Load IR. I noticed that one tube was red plating so did the usual checks such as swapping tube positions around but the...