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  , 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.

No need to clean then,you can leave the sticker on it (BTW HG means High Grade).

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.

[Rawk777]

Just to be sure... it's ok to swap tubes while the unit is on?

[vansinn]

Just to be sure... it's ok to swap tubes while the unit is on?

No!

[Iperfungus]

Just to be sure... it's ok to swap tubes while the unit is on?

Well...if you want to do a big damage and/or harm yourself, yes...  :waving-banana-smiley-emoticon
Otherwise, no.  :)) :)) :))

[MarshallJMP]

No not really.

[Rawk777]

I did a search on different forums, and a lot of people says it's ok to hotswap preamp tubes on a tube head if the amp is on standby.

i.e. http://www.ebay.com/gds/Want-a-better-amp-Change-your-preamp-tubes-/10000000001202478/g.html

I thought the stanby of a tube head was affecting only the power tubes.

[Iperfungus]

Well...generally speaking, I would not put hands and disconnect or swap ANY component inside something connected to a socket and powered on with some internal high voltage...unless I would try to kill myself.   

Usually, when I need to service my amp, I power it down and disconnect main cable from wall socket...
You never know...and it's also better to wait some minutes to let capacitors discharge.

By the way, you cannot put a MP-1 in standby...

[MarshallJMP]

The standby switch switches the high voltage of all the tubes off.

[Iperfungus]

The standby switch switches the high voltage of all the tubes off.

If you have a standby switch... 

[vansinn]

If anyone does a tube hotswap, then please have the device hooked to amp/speaker and record what it sounds like, preferably a video posted to Youtube
- not that I think anyone will die; it's purely cuz tis an experience I haven't tried, and I'd love to know what it might be like.. :banana-trip:

[Iperfungus]

If anyone does a tube hotswap, then please have the device hooked to amp/speaker and record what it sounds like, preferably a video posted to Youtube
- not that I think anyone will die; it's purely cuz tis an experience I haven't tried, and I'd love to know what it might be like.. :banana-trip: