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  #16  
Old 08-01-2022, 03:46 AM
Bob Womack's Avatar
Bob Womack Bob Womack is offline
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As far as replacing power and preamp tubes is concerned, preamp tubes typically last a lot longer than power tubes. I've got a set of 12AX7 preamp tubes in a Marshall that have been there for twenty-seven years and are going strong. They have survived a burned out pair of EL-34 power tubes.

Bob
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  #17  
Old 08-01-2022, 07:31 AM
Paleolith54 Paleolith54 is offline
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Originally Posted by ChrisN View Post
Someone has to mention the potential life-threatening voltages (400+) that dwell within the amp, in its capacitors that store juice. Touching the wrong thing (and there are several of them under the hood, not easily recognizable) can kill you. Folks opening the amp should learn about discharging capacitors as a first step to any investigation, verify discharge with a multimeter, and even then, the underinitiated should consider working via plastic/wooden stick when poking/prodding, working with one hand behind their back, etc. Safety first, and amps can be dangerous.
All absolutely true, but since we're talking about this: that doesn't mean folks shouldn't change tubes, use DeOxit like Bob described above, or even remove the amp from the chassis if it needs to be shipped for repair or if (like my Mesas) it's the only practical way to change pre-amp tubes. Just be sure the amp is unplugged and keep your fingers away from anything that looks like a circuit.
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  #18  
Old 08-01-2022, 10:55 AM
rmp rmp is offline
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Originally Posted by Paleolith54 View Post
All absolutely true, but since we're talking about this: that doesn't mean folks shouldn't change tubes, use DeOxit like Bob described above, or even remove the amp from the chassis if it needs to be shipped for repair or if (like my Mesas) it's the only practical way to change pre-amp tubes. Just be sure the amp is unplugged and keep your fingers away from anything that looks like a circuit.
I've never seen a tube amp where it's physically possible to hurth yourself by seating tubes in their sockets? and if you don't unplug it first, you're probably better off with a modeling amp anyway.


Of course, taking the amp chassis out of the cab to work on BIASing, yea.. not something you do unless you know what you're about.
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  #19  
Old 08-06-2022, 09:41 PM
RickRS RickRS is offline
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Originally Posted by clintj View Post
Regarding blue glow in power tubes, a light blue glow on the gas is normal and was considered a sign of excellent vacuum by the likes of Sylvania and other tube makers.
Beat me to it.
Agreed. There is nothing wrong with a blue glow in your power tubes. Same with getting fingerprints on the glass. The tube isn't going to get hot enough for the oil to cause them to break.
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