[whirlwind]

Some real killer 421A pics guys....those are some great collections of those tubes

 

[JKDJedi]

Very nice tubes. Thanks for posting.

Here are some later WE421A from 1981, 1985, 1972

I was gonna post a pic of my one 76' but then this.. ^ wow...what a collection. Nice.

 

[tubebuyer2020]

Is it normal for a tube (6AS7G in this case) to get darker on the inside (smoky dark, like someone lit a match and the glass acquired a darkish, smoky but uniform color) and for the chromium to all of a sudden cover the top whereas before use it was just in the lower part of the tube?

It happened while using for 3-4 hours, did not pay attention during, just saw it after. It works and sounds fine... is this just the inner gas settling or something? It's the first time I use this particular tube.

A few photos would be interesting.

 

[JTbbb]

Any 421a collectors out there consider some form of exchange for a pair of Bendix Slotted Graphite Plate 6080WB’s, or a pair of Mullard Brown Base ecc32’s?

 

[CaptainFantastic]

A few photos would be interesting.

Right, so here is the change. It is even more dramatic in real life than the photos suggest.

Full disclosure, I always have same routine - turn on amp, no volume, plug in headphones, let tubes warm up 5-10 minutes, play music for however long - keep amp under some music load even if I walk away 5-10 minutes, then turn off sound from source, turn volume on amp to zero, unplug headphones, turn off amp. On this occasion I actually forgot the amp on after unplugging the headphones for some 20-30 minutes. Could this have caused it?


Before - clear as day at the top:




After - smoky glass and top you see mirror in picture, it looks like chromium in real life.

 

[tubebuyer2020]

Right, so here is the change. It is even more dramatic in real life than the photos suggest.

Full disclosure, I always have same routine - turn on amp, no volume, plug in headphones, let tubes warm up 5-10 minutes, play music for however long - keep amp under some music load even if I walk away 5-10 minutes, then turn off sound from source, turn volume on amp to zero, unplug headphones, turn off amp. On this occasion I actually forgot the amp on after unplugging the headphones for some 20-30 minutes. Could this have caused it?


Before - clear as day at the top:




After - smoky glass and top you see mirror in picture, it looks like chromium in real life.

Well, an ebay seller would have said "NOS/NIB rare chrome-dome bad boy GEC 6AS7G"!
On a serious note - no idea, perhaps the temperature was high enough to vaporise and migrate the getter flash deposit?

 

[tubebuyer2020]

https://www.diyaudio.com/forums/tubes-valves/189001-resurrecting-weak-tubes.html

https://www.diyaudio.com/forums/tubes-valves/316578-regenerating-tubes-experience.html

https://www.diyaudio.com/forums/tubes-valves/231203-baking-tubes-procedure-help.html

 

[JKDJedi]

Right, so here is the change. It is even more dramatic in real life than the photos suggest.

Full disclosure, I always have same routine - turn on amp, no volume, plug in headphones, let tubes warm up 5-10 minutes, play music for however long - keep amp under some music load even if I walk away 5-10 minutes, then turn off sound from source, turn volume on amp to zero, unplug headphones, turn off amp. On this occasion I actually forgot the amp on after unplugging the headphones for some 20-30 minutes. Could this have caused it?


Before - clear as day at the top:




After - smoky glass and top you see mirror in picture, it looks like chromium in real life.

That the same tube?wow.. looks like some getter material imploded to the very top..

 

[Dogmatrix]

Right, so here is the change. It is even more dramatic in real life than the photos suggest.

Full disclosure, I always have same routine - turn on amp, no volume, plug in headphones, let tubes warm up 5-10 minutes, play music for however long - keep amp under some music load even if I walk away 5-10 minutes, then turn off sound from source, turn volume on amp to zero, unplug headphones, turn off amp. On this occasion I actually forgot the amp on after unplugging the headphones for some 20-30 minutes. Could this have caused it?


Before - clear as day at the top:




After - smoky glass and top you see mirror in picture, it looks like chromium in real life.

I have seen some GEC tubes develop small silver spots directly over the filament tubes but nothing as dramatic as that . I always thought it was something that had developed over years of use and took it as a sign of age . Carbon deposit is normal , quite common in 5998 types but again I thought it developed over time .

 

[tintinsnowydog]

Right, so here is the change. It is even more dramatic in real life than the photos suggest.

Full disclosure, I always have same routine - turn on amp, no volume, plug in headphones, let tubes warm up 5-10 minutes, play music for however long - keep amp under some music load even if I walk away 5-10 minutes, then turn off sound from source, turn volume on amp to zero, unplug headphones, turn off amp. On this occasion I actually forgot the amp on after unplugging the headphones for some 20-30 minutes. Could this have caused it?


Before - clear as day at the top:




After - smoky glass and top you see mirror in picture, it looks like chromium in real life.

That's really fascinating, I wouldn't expect a getter-flash like appearance to develop so quickly especially under normal operating temperatures. Does the getter look any different? The rest of the tube also looks a bit darker in the second photo but that may just be the angle?

I have an A1834 which has a patch of chrome at the top but it came to me like this- it hasn't really changed much with extended use. The others I have seen are all clear tops.

 

[leftside]

I was gonna post a pic of my one 76' but then this.. ^ wow...what a collection. Nice.

You still should! Always good to see these vintage tubes.

 

[maxpudding]

Probably just another post about the importance of cleaning your tube pins. I've just managed to fix a 6080WB tube that didn't have sound coming from the right channel at all by using a 400 grit sandpaper and some contact cleaners.

@leftside, that's some hardcore tube porn

 

[HTSkywalker]

Probably just another post about the importance of cleaning your tube pins. I've just managed to fix a 6080WB tube that didn't have sound coming from the right channel at all by using a 400 grit sandpaper and some contact cleaners.

@leftside, that's some hardcore tube porn

Re-soldering also makes wonders

 

[tintinsnowydog]

To add to the tube parade- a brief history of the MOV A1834/CV2523

Earlier, pre 1954 black base A1834. The labels are painted on and can rub off! HK (1952) and JJ (1953) date codes.

Brown (curved) base design starting from 1954 (KE date code). Internals seem identical to the black base so far. Label is more resilient now (right)!

Brown (straight) base. Looks like the cup getter was introduced from 1955 onwards replacing the older rectangular getter. Some time after, the distinctive short bottle design was adopted. Straight and curved bases are both used and do not necessarily indicate vintage, probably depending more on the specific order and desired environment of use at the time.

CV2523 designation.

I don't have any tubes later than 1968, but I'm aware that they switch to the 4 digit codes after Z= 1968 (YYWW). They can then have halo getters (but never flying saucers!)

 

[leftside]

To add to the tube parade- a brief history of the MOV A1834/CV2523

Earlier, pre 1954 black base A1834. The labels are painted on and can rub off! HK (1952) and JJ (1953) date codes.


Brown (curved) base design starting from 1954 (KE date code). Internals seem identical to the black base so far. Label is more resilient now (right)!


Brown (straight) base. Looks like the cup getter was introduced from 1955 onwards replacing the older rectangular getter. Some time after, the distinctive short bottle design was adopted. Straight and curved bases are both used and do not necessarily indicate vintage, probably depending more on the specific order and desired environment of use at the time.

CV2523 designation.


I don't have any tubes later than 1968, but I'm aware that they switch to the 4 digit codes after Z= 1968 (YYWW). They can then have halo getters (but never flying saucers!)

Informative post. Thanks. Those first two pairs you posted are very rare. Very strange for MOV/GEC to do this with the getters. Usually the cup getters came before the D getters. I also have a GEC 6AS7G brown base from the 60's with a D getter, but I consider this to be an anomaly.

I know with the KT66 the very earliest versions used a flat solid saucer like getter, then inverted cup and then twin halos starting early 1960's.