Let's Get Technical > Tubes (preamp/Input/Buffer)
Tube rolling questions & signs of dying tubes?
DesmoBob:
New tubes:
:whoohoo!:
JJ ECC83S (Ruby) & Mullard ECC83 long plate reissues. The OE tubes in the background are just for photographic efffect.
Currently in the MP-1 are Groove tubes (about 20 years old). After about 45 minutes of play, the total output of the preamp appears to drop by about 20%. It just gets more quiet overall, and I have to increase the output volume of the MP-1. Is this a sign of dying tubes? But wouldn't dying tubes be more quiet as soon as I turn it on, not just after a period of time after being warmed up?
Questions about tube rolling. Can I swap out tubes while they're still warm? Or do I wait until they're stone cold? I don't want to damage anything. But at the same time, I don't want to wait unnecessarily long because I have multiple combinations to try out.
edit:
More questions--the new tubes have marker pen numbers written on them, I assume from testing. Is it okay to leave these on, or should I clean them off? Also, the JJs have an "HG" sticker on them (high gain). Should this be removed?
rnolan:
Hey DB, nice array of tubes :thumb-up: , it does seem a bit strange that the old tubes are ok for 45 mins then you loose level. The easy test is put in a new pair, if the same thing happens, something else is degrading after heat/time.
I probably wouldn't worry about the pen markings (though you could rub it off, probably with alcohol or metho). I'd take off the sticker though, it would probably be ok but to be sure...
Rolling the tubes while their warm is ok to do (don't burn yourself obviously). I remember posting that I clean off the slight oil residue left from your finger prints (this comes from changing light filaments in PAR 64s etc but they run way hotter than tubes and the finger prints can cause them to fail (creates a hot spot)). IIRC MJMP advised back then that it wasn't necessary to be that pedantic with tubes.
MarshallJMP:
No need to clean then,you can leave the sticker on it (BTW HG means High Grade).
And yes tubes can loose gain after they are warmed up,one of my tubes did this in my 3TM,after about 35 min of playing the gain would drop slightly and progressive.Replaced them ,now no more problems.Tubes are still mechanical things and they can last 20 years or 2 seconds.Now the quality of current production is nowhere as good as in the old days.
DesmoBob:
Thanks for the tips. I think I'll wear socks on my hands.
--- Quote from: MarshallJMP on July 08, 2015, 11:47:59 AM ---No need to clean then,you can leave the sticker on it (BTW HG means High Grade).
--- End quote ---
Oh haha even better. I thought HG meant high gain because I requested it.
MarshallJMP:
My guess those JJ's are tested by Ruby?Usually they put HG stickers on them.
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