KT88 zero bias reading

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Here's an interesting one for you guys. My amp has had a few KT88s within the last several months that will go to zero bias. The problem has been on the same channel, but in two different tube sockets. The tube will start out reading a normal bias and then drop to zero after warm-up. There are no loud noises, blown fuses or other dramatics. The last one to act up made ticking noises every 2-3 seconds similar to the sound of the end groove of a record then read zero bias. The tube then worked again and read normal the next day and then the day after a single tick sound and zero bias again. If you switch the tube that reads zero to another socket you will get the same result, zero bias after warm-up. I've had several tube amps, but never experienced this exact situation. Any help or similar experiences appreciated. Thanks.

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Kimber Kable

Topic - KT88 zero bias reading - Buddah 22:21:16 03/29/06 (3)

Re: KT88 zero bias reading - tvr2500m 07:29:08 04/01/06 (0)

Re: KT88 zero bias reading - IdlerWheel 06:01:17 03/30/06 (1)

Sounds like a bad internal connection in the tube - Chris O 06:25:28 03/30/06 (0)

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