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Stabilizing a Marshall Major?

4/25/2003 9:02 PM
Tim Gagan	Stabilizing a Marshall Major? I've ended up with a Marshall Major in my possession, and I was thinking of using it as a bass head. However, I've heard it mentioned a few times lately that they are unstable tube eaters. I'm wondering what the causes of their instability and hunger for tubes are, and if there's anyway to mitigate them. Nothing in the schematic jumps out at me. The voltage is high, sure, but it doesn't seem murderously high for a 6550/KT88 (646vdc in mine with no tubes in place, and the GE book lists 6550's max plate voltage at 660. SVT's are much higher than that anyway). Is it the screen voltage that's too much? Thanks to anyone with Major experience that can offer any insight.

4/25/2003 9:02 PM

Tim Gagan

Stabilizing a Marshall Major?

I've ended up with a Marshall Major in my possession, and I was thinking of using it as a bass head. However, I've heard it mentioned a few times lately that they are unstable tube eaters. I'm wondering what the causes of their instability and hunger for tubes are, and if there's anyway to mitigate them. Nothing in the schematic jumps out at me. The voltage is high, sure, but it doesn't seem murderously high for a 6550/KT88 (646vdc in mine with no tubes in place, and the GE book lists 6550's max plate voltage at 660. SVT's are much higher than that anyway). Is it the screen voltage that's too much?
Thanks to anyone with Major experience that can offer any insight.

Replies:

Ray Ivers Tim,I've heard the term 'un... -- 4/25/2003 11:03 PM
LFOscalator The Major was originally tubed with... -- 4/25/2003 11:37 PM
Tim Gagan Thanks for the info guys. Fortunat... -- 4/27/2003 5:10 AM