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Re: [Amps] GS35B Idle Current drifting up.

Subject: Re: [Amps] GS35B Idle Current drifting up.
From: Steve Thompson <>
Date: Sat, 21 Dec 2013 22:24:00 +0000
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The tube was one offered to me for the cost of postage, I don't know its history. It showed no signs of life and high hipot leakage so I opened it up.

I think the photos were taken with my first digital camera - Olympus C1400XL. Not so many pixels, but a large diameter lens and good optics.

I've seen similar looking damage in smaller tubes attributed to cathode overheating when airflow was inadequate. Other than keeping it cool, I'd suggest you run the lowest plate supply you can for the gain/power you need, avoid hot switching relays and look after the loading.


Nice clear photos. What would have made that happen? And how to best avoid it from happening to... lets say, my amp?


I opened and photographed a dead one a while ago. The pictures are

Would the drift happen if a tiny bit of cathode material evaporated and migrated to the grid?


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