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Hi, This is my first post and just looking for some quick advice please. I have searched but not sure of what I've read.
I have a Jadis DA30 Integrated Amp. Self Biasing. I have just received NOS EI KT90 tubes which are similar to those it was originally supplied with.
After about half an hours use. I saw one was glowing a lot. Bright Red and not what I had seen previously on the KT90s I used to have. Swapping the Tubes around the "problem" followed the tube.
Putting a thermocouple on all 4 tubes I get about 120°C on 3 of them and the rogue is at 150°C.
My old EL34s are back in but I just have to get the KT90s running as the sound is so much better and my wife spent a lot of money on them.
What would be the advice please? Nobody I know of has a tube tester in Ireland!
Andrew
Follow Ups:
If the problem followed the tube it is probable a bad tube. Should be able to get a replacement from where your wife purchased it.
Alan
Was the plate turning red? If so do not put it back. There are 3 or 4 versions EiKT90's. That was a common problem with I believe was late production type 3's. Hopefully Jim McShane will correct me if I'm wrong. I have both the type 2 and type 3 and have had no problems. Great tube and that's what I'm using now in my Octave V110.
You are correct, the suspect tube could be a type III which had red plating issues after the initial production (and the NATO war in the Balkans!).
Get a replacement tube! Don't use that one.
Hey Jim - How many versions of the Ei KT90 were there? I read somewhere they had a type IV.
The type III was made with two different getter patches (a.k.a. "pills") - one was round and the other was square. EveAnna Manley called them types III and IV, but since the shape of the getter was the only (and very minor) difference I regard them all as type IIIs.
Gotcha - Thanks for the update. One last question - was it the early or late production type III's that had the 'red plate' symptom?
Thanks
George
Later production. The problem began about the same time as the NATO intervention in the Balkans.
Thanks again Jim. You cleared up a lot for me
George
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