[attmci]

The tube has no date code on the base or on the glass (maybe it was deleted?). All I can see is:

Besides that only TUNG SOL / Made in USA. It came in generic boxes, so no information on them either.

A similar construction I've found here, on a tube labeled as Tung Sol 421A:
https://www.ukaudiomart.com/details/649372022-tungsol-421a5998-power-tubevalve/images/1612914/

However, soundwise, the tube sounds to me similar to a 5998, and not as WE 421A (yep, I own both and I hear clearly differences between them). So it is a tube sounding as 5998, labeled sometimes as Tung Sol 421A and it has top and side O-getter. But regarding the sound I would need more time since I only had a few hours on them.

Because it is different than everything I've seen I try to find out its story.

All 421A has bottom getters, and clear-top. If you can find some 5998 like those, grab it.

For manufacture date, does the 322xxxx ring a bell?

 

[JKDJedi]

All 421A has bottom getters, and clear-top. If you can find some 5998 like those, grab it.

For manufacture date, does the 322xxxx ring a bell?

It's Tung Sol EIA code (322), my guess is the tube is 1968 34th week...

 

[OctavianH]

All 421A has bottom getters, and clear-top. If you can find some 5998 like those, grab it.

For manufacture date, does the 322xxxx ring a bell?

It does indeed ring a bell, but then I have the following question:

The third tube from left here has the code 3226731 which you said it means 1967 the 31th week. However above the 5998 logo we see the 5711 which I thought it means 1957 11th week. Well, which is the date code?

 

[attmci]

It does indeed ring a bell, but then I have the following question:

The third tube from left here has the code 3226731 which you said it means 1967 the 31th week. However above the 5998 logo we see the 5711 which I thought it means 1957 11th week. Well, which is the date code?

1967 sounds more likely to be the manufacture date for the green labeled tube.

 

[JKDJedi]

1967 sounds more likely to be the manufacture date for the green labeled tube.

I concur, the 5711 is nowhere near the 322, I know, wishful thinking to have a 50' 5998, you might have to grab a JAN 5998 for a 1950's, nice collection by the way.

 

[OctavianH]

I concur, the 5711 is nowhere near the 322, I know, wishful thinking to have a 50' 5998, you might have to grab a JAN 5998 for a 1950's, nice collection by the way.

Honestly I do not care in which year they are manufactured, I just wanted to understand which is the date code since 5711 was possible to be read as a date YYWW. Thanks for help, everyone!

 

[JKDJedi]

1985? Huh. Well for sure if there were 421a tubes being made in 1985, it wasn't Tung Sol making them, as Tung Sol was long gone by then. Cetron, who bought Tung Sol, continued to make some of Tung Sol's tubes like the 6336, sold under the Cetron name, for some time, maybe even as late as the 1980's. But not the 5998, I don't believe. So perhaps WE had to start making the 421a, and thus the slight design change.

There's discussion that it was Western Electric who initially sent a formal request (1950) to the RTMA (Radio-Television Manufacturers Association) for a special purpose code be assigned to the 421a, that code assigned by the RTMA was *5998. 421a began it's use in 1948 prior to the request, 421a was before the 5998, and it still continued after the 5998... so ...

What's also interesting is if you go to Radio Museum website... they list the Developer of the 5998 as who..you guessed it...Western Electric.

https://www.radiomuseum.org/tubes/tube_5998.html

 

[cddc]

Radiomuseum.org is nothing but a forum, most info on radiomuseum.org was uploaded by individual members, so mostly correct, but definitely not 100% correct, as far as I know.

That said, there is nothing wrong with WE being the developer of 5998/421A tubes. It's indeed WE who designed / developed 5998 and 421A, but as far as I know it was Tung Sol who manufactured these tubes.

 

[cddc]

I find an interesting trend, owners, especially tube vendors like to stress 421A sounds much better than the seemingly identical 5998. Vendors of course hope to reap more $$$ for any possible cause, even if the cause can be fake. Users on the other hand are often biased towards higher-price tubes or tubes they own - this can be straightened out by blind test.

But I trust opinions from senior members like @gibosi, @Skylab , @Dubstep Girl , etc.

Some people think WE 421A is different than Tung So 5998 because they have different transconductances (on paper WE 421A has 20,000 uMhos, and 5998 has 14,000 uMhos). But I also read that the higher transconductance of WE 421A was caused by using higher testing plate and grid voltage. I think whether WE 421A and 5998 have different transconductances or not can easily be verified by a tube tester, just use the same settings (i.e. same plate voltage and same grid voltage) to test both WE 421A and 5998. I noticed 2 cases recently, both tested WE 421A tubes using the 5998 settings, and the test results were around 14,000 uMhos (or 100% of NOS 5998) and 16,000 uMhos (or 114% of NOS 5998). From the 2 cases it seems WE 421A has similar measured transconductance as 5998's if it is tested under the same plate voltage and grid voltage as 5998's. We need more cases for certainty for sure.



Ref of two WE 421A measured under 5998 settings:
https://www.head-fi.org/threads/darkvoice-336i-336se-tuberolling-partii.348833/post-15809681
https://www.head-fi.org/threads/price-drop-western-electric-421as-nos-nib.907974/

 

[JKDJedi]

I find an interesting trend, owners, especially tube vendors like to stress 421A sounds much better than the seemingly identical 5998. Vendors of course hope to reap more $$$ for any possible cause, even if the cause can be fake. Users on the other hand are often biased towards higher-price tubes or tubes they own - this can be straightened out by blind test.

But I trust opinions from senior members like @gibosi, @Skylab , @Dubstep Girl , etc.

Some people think WE 421A is different than Tung So 5998 because they have different transconductances (on paper WE 421A has 20,000 uMhos, and 5998 has 14,000 uMhos). But I also read that the higher transconductance of WE 421A was caused by using higher testing plate and grid voltage. I think whether WE 421A and 5998 have different transconductances or not can easily be verified by a tube tester, just use the same settings (i.e. same plate voltage and same grid voltage) to test both WE 421A and 5998. I noticed 2 cases recently, both tested WE 421A tubes using the 5998 settings, and the test results were around 14,000 uMhos (or 100% of NOS 5998) and 16,000 uMhos (or 114% of NOS 5998). From the 2 cases it seems WE 421A has similar measured transconductance as 5998's if it is tested under the same plate voltage and grid voltage as 5998's. We need more cases for certainty for sure.



Ref of two WE 421A measured under 5998 settings:
https://www.head-fi.org/threads/darkvoice-336i-336se-tuberolling-partii.348833/post-15809681
https://www.head-fi.org/threads/price-drop-western-electric-421as-nos-nib.907974/

Most of my info came from one of those senior members you mentioned above. I compared both data sheets closely yesterday. Very close, what's interesting is that they have variable data depending on current as you mentioned. The 5998 could be pushed near 421a specs if needed, thinking up to 17000, the 421a appear to better built as far as I can tell. A highly sought after tube.

 

[leftside]

Radiomuseum.org is nothing but a forum, most info on radiomuseum.org was uploaded by individual members, so mostly correct, but definitely not 100% correct, as far as I know.

That said, there is nothing wrong with WE being the developer of 5998/421A tubes. It's indeed WE who designed / developed 5998 and 421A, but as far as I know it was Tung Sol who manufactured these tubes.

How could TungSol have manufactured these tubes in 1985? They no longer existed as a company. I have 421A tubes with a Western Electric 1985 date stamp.

 

[cddc]

How could TungSol have manufactured these tubes in 1985? They no longer existed as a company. I have 421A tubes with a Western Electric 1985 date stamp.

I have no idea. Few tube manufacturers made into the 80's, most of them were gone by the late 70's I think.

Two possibilities:
1. the date stamp could be wrong - WE was taken over by AT&T Technologies, Inc on January 1, 1984, not sure if WE branded tubes were still in production after that date;
2. WE started to manufacture its own 421A after Tung Sol ceased operations.

 

[leftside]

I have no idea. Few tube manufacturers made into the 80's, most of them were gone by the late 70's I think.

Two possibilities:
1. the date stamp could be wrong - WE was taken over by AT&T Technologies, Inc on January 1, 1984, not sure if WE branded tubes were still in production after that date;
2. WE started to manufacture its own 421A after Tung Sol ceased operations.

I think it's the latter. I have three pairs of WE 421A. From 1972, 1981 and 1985. Here is a photo of one from 1981 and another from 1985.

 

[JKDJedi]

I think it's the latter. I have three pairs of WE 421A. From 1972, 1981 and 1985. Here is a photo of one from 1981 and another from 1985.

I think it's the latter. I have three pairs of WE 421A. From 1972, 1981 and 1985. Here is a photo of one from 1981 and another from 1985.

Have one from 76' that looks a lot like the 85' there. Wondering what happened in 81' that had them going top getter vs bottom.

 

[leftside]

Have one from 76' that looks a lot like the 85' there. Wondering what happened in 81' that had them going top getter vs bottom.

Good spot. For that, I have no idea. The TungSol 5998 also has multiple different variations...