[JTbbb]

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!)

Nice post and so knowledgeable! Are there enough pictures here to give me some information on these?

 

[gibosi]

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.

My experience is the same as yours. I have three pairs of GEC 6AS7G -- 1949, 1956 and 1960, and all have the inverted cup getters. In fact, 1949 has two small inverted cup getters. And it appears to me that GEC began to use D getters in 6AS7 sometime after 1960.

 

[gibosi]

Nice post and so knowledgeable! Are there enough pictures here to give me some information on these?

Z is the factory, MO Valve Company, Hammersmith.

The two letters, in your case, SJ, correspond to the date. AA is 1945, January so SJ is 1960, September. (assuming I have calcuated this correctly .

The following link will help you decipher these factory and date codes:

https://mullard.org/blogs/news/83886851-cv-numbers-and-uk-military-date-and-factory-codes

 

[exchez]

Z is the factory, MO Valve Company, Hammersmith.

The two letters, in your case, SJ, correspond to the date. AA is 1945, January so SJ is 1960, September. (assuming I have calcuated this correctly .

The following link will help you decipher these factory and date codes:

https://mullard.org/blogs/news/83886851-cv-numbers-and-uk-military-date-and-factory-codes

Part of the fun of tube rolling is employing some form of minor code breaking just to figure out what your spending all your money on

 

[leftside]

Part of the fun of tube rolling is employing some form of minor code breaking just to figure out what your spending all your money on

GEC are pretty easy. Philips and later Mullard are possible, but sometimes it’s like cracking a secret code. Good luck with early Mullard (before they adopted the Philips system). I’ve yet to meet someone who can crack those codes completely.

Edit: GEC pre Jan 1945 are also tough to decipher. I have a few early KT66 from then, and the best I can find is “wartime”.

 

[leftside]

My experience is the same as yours. I have three pairs of GEC 6AS7G -- 1949, 1956 and 1960, and all have the inverted cup getters. In fact, 1949 has two small inverted cup getters. And it appears to me that GEC began to use D getters in 6AS7 sometime after 1960.

Post up some photos of those 1949 GEC 6AS7G my friend. Would be interesting to see those getters.

 

[gibosi]

Post up some photos of those 1949 GEC 6AS7G my friend. Would be interesting to see those getters.

Here you go.

 

[leftside]

Here you go.

Nice. And with remnants of that early Marconi "shield" logo.

 

[tintinsnowydog]

Here you go.

Such a nice pre-1950 pair!

Regarding getters, MOV probably used whatever they had on hand at the time. Those small cup getters are typical of the MOV metal base 6J5 from similar vintage, so possibly that was what was readily available in 1949. The rectangular D getters and large inverted cup getters were probably used interchangeably until mid/late 60s. Then we see the halo getter making an appearance after that, but some 6J5 for instance even with the exact same date code and other internals can have halo or rectangular getters.

 

[rlawry]

Hi All: I am a relative newbie to this forum and have a question about T-S 5998/421A tubes. If the tube is marked as a 5998/421A tube, which one is it: 5998 or 421A? Or is it a unique version of this tube? It seems as though most, if not all, of these tubes are dual-bottom getter tubes with clear tops like all of the 421A and some of the older 5998s. I apologize if this has been answered in the past but haven't gotten through all 521 pages so far. Thank you.

 

[Odin412]

I picked up a couple of vintage Svetlana 6AS7G tubes from Russia via eBay. Very nice tubes - they are excellent in my Woo Audio WA3. Reasonable price too.

 

[exchez]

Hi All: I am a relative newbie to this forum and have a question about T-S 5998/421A tubes. If the tube is marked as a 5998/421A tube, which one is it: 5998 or 421A? Or is it a unique version of this tube? It seems as though most, if not all, of these tubes are dual-bottom getter tubes with clear tops like all of the 421A and some of the older 5998s. I apologize if this has been answered in the past but haven't gotten through all 521 pages so far. Thank you.

To distinguish a 421A from a 5998: "[The 421A] always have dual bottom halos or D getters with spiral wound "pigtails" filament wiring >>> 5998 have straight filament wiring and cleartop 5998s are very rare."

Apparently Tung Sol made some tubes labeled as 421A: "Basically it's a Tung Sol 5998 labelled "421A" and has the black 5998 plates. Do not have one myself but pretty sure it's either the same tube as the 5998 with different getters or a 5998 with 421A specifications without the WE 421A construction differences."

Info from: http://the-key.enix.org/~krystal/review-tube-bottlehead.html

 

[leftside]

To distinguish a 421A from a 5998: "[The 421A] always have dual bottom halos or D getters with spiral wound "pigtails" filament wiring >>> 5998 have straight filament wiring and cleartop 5998s are very rare."

I'll post up a pair of Chatham/TungSol 5998 with bottom getters and cleartop in a few days.

Apparently Tung Sol made some tubes labeled as 421A: "Basically it's a Tung Sol 5998 labelled "421A" and has the black 5998 plates. Do not have one myself but pretty sure it's either the same tube as the 5998 with different getters or a 5998 with 421A specifications without the WE 421A construction differences."

Here is a 421A labelled tube with top getters. Now, you say these must be TungSol? I'm not an expert on Western Electric date codes, but I always believed these tubes were from 1981 which means they would have to be manufactured by Western Electric as TungSol didn't exist then. Can anyone else comment on this "813" date code. Perhaps I got it wrong.

 

[mayurs]

Got a Chatham 6080WA thinking that it will be same as my Tungsol 6080 but it is quite different to the Tungsol. No extra mica supports and the top end looks quite different. Is it a Raytheon 6080 variant?

 

[rlawry]

@leftside, so if I am to understand correctly, the above tubes labeled as WE421A break both rules of distinguishing the 5998 from 421A, having top getters and what appears to be non-coiled cathode heater wiring. Therefore, it is most likely a 5998 labeled as a 421A? It seems as though there are almost always labelling or re-labelling differences that go against accepted convention.