Testing old tubes to see if they've redplated?

[Shinozoku]

I recently helped my frined retube his Line 6 Spider Valve (he got Sovtek 5881WxTs for it, which I really wish were exactly what was in his amp before. Instead they're the 5881/6L6WGC) because two of his old power tubes were redplating, but he doesn't really remember which ones.

How can I test to see if they're still good without putting them in my amp? Or can I just pop the pair I think is good in and cross my fingers?

 

[Julia]

Why didn't he just get a quad if he needs 4. Chances are the other two are about to go bad as well.

There may be some telltale discoloration on the plate or darkening of the glass on the side of the tubes.

 

[Shinozoku]

Why didn't he just get a quad if he needs 4. Chances are the other two are about to go bad as well.

There may be some telltale discoloration on the plate or darkening of the glass on the side of the tubes.

He did get a quad. He replaced every tube in the amp (birthday present form his mum). He just gave me the old tubes as payment for helping him, and we couldn't really remember which were which (should have checked by turning it on first, maybe).

One one of the ones we think is one of the "bad" tubes, it seems that the top plate (which normally looks satiny or dusty) is smoother and glossier on part of it. Is that something I would look for?

 

[Julia]

I will post a couple photos or my dead redplated tubes once my other computer finishes defragging.

Now on that subject, HOW? Just how can a disk get 70% fragmented in two weeks when all I use that one for is the internet? Yes I have a firewall, and yes I'm behind a router, and yes I sweep it every week, and yes I have an antivirus prg.

 

[Julia]

Two E34Ls that redplated on my Lynch Box. Note the discoloration of the glass. I didn't get a good shot of the other side of the tube, but if you look on them you might find an outline that's kind of whitish on the plate as well.