[mordy]

No doubt. As far as 6080 tubes go, I have found solace with tung sol/chatham 6080WA.

Hi S01,
I have pair of the Chatham 6080. What I noticed about them was that they have a very punchy bass, but in my setups I could not find the right synergy. Just goes to show that the tubes of choice have to be tailored to the amp you are using.
Part of the fun of tube rolling is finding the right combination that works for you and suits your taste. For me, I also enjoy finding the tubes without paying through the nose. Bought the Chathams from some housewife for very little. After I payed her, she sent an email calling me brave for buying an untested pair. I figured that if someone had been saving saving these tubes for over 50 years they probably are good, and they were.....

 

[attmci]

https://www.ebay.com/itm/Western-Electric-421A-5998-Pair-Vacuum-Tubes/184100629052

Used 421A/5998. New should be close to 20000 micromhos.

 

[cddc]

These are 6as7g unmark base with copper pin. Are these possibly Chantham/Tungsol type? If not who is the maker of the tube? Many thanks for the clarification

I think these are GE 6AS7G tubes.

I was checking on some GE 6AS7G tubes recently, and noticed some small differences they have against TungSol/Chatham 6AS7G tubes - mainly the 2 spikes on each plate are much shorter. The 2 spikes on GE only extend 1/4 of the plate height while on TungSol/Chatham they extend almost 1/2 of the plate height.

I understand a popular conclusion here is that only 2 manufacturers in the US made 6AS7G tubes, mainly RCA and TungSol/Chatham. But I suspect a possible 3rd US 6AS7G manufacturer due to the small difference mentioned above.

 

[mordy]

To the best of my knowledge the GE tubes were made by RCA.
Head fier gibosi would have the information.

 

[gibosi]

Well, to my eyes these look like Chatham / Tung-Sol. As to small differences visible to the eye, I think it is important to remember that the 6AS7G was manufactured beginning in the late 1940's through at least the late 1960's. And with the development of new processes and materials plus feedback from the field, the internal construction inevitably changed over the years.

GE was a major player in the vacuum tube industry after WWII. And I suspect that if they did in fact manufacture the 6AS7G we would see lots of them on eBay. Rather, it appears that GE decided to introduce the 6AS7GA in the early 1950's. And I have seen nothing to suggest that there was a third US manufacturer of the 6AS7G.

 

[cddc]

Thanks a lot @mordy and @gibosi

Indeed most GE 6AS7G’s I have seen are rebranded RCA 6AS7G’s - those with some black skirts under the bottom mica.

The ones I quoted look exactly the same as the few GE 6AS7G’s that come with TungSol/Chatham style innards. However, they are some small differences. TungSol 6AS7G’s normally have some small silver colour bands at the top and bottom of plates. Chatham 6AS7G sometimes do not have these sliver color bands on plates, but the 2 spikes on each plate extend much longer than the ones on GE 6AS7G’s (1/2 vs 1/4).

It’s very likely, as @gibosi suggested, GE sourced their 6AS7G tubes from RCA and TungSol/Chatham and put a GE label on them. Also GE might send some special requests/specs on 6AS7G to TungSol/Chatham, which can partially explain the difference in spike length. Or GE did indeed manufacture some 6AS7G tubes, but not in large quantities, then quickly turned their 6AS7G production lines into 6AS7GA lines (not very likely, but possible)

I think the ultimate test is to hear them in an amp and compare the sound signature. TungSol/Chatham 6AS7G’s are very good 6AS7G/6080 tubes, but not up to the top tier, IMHO. I have already got 2 TS/Chatham 6AS7G tubes, so not so eager to grab a GE 6AS7G to compare. Hopefully someone with both can chime in.

 

[cddc]

The 5998's never come out of my wa22, when I owned a wa7/tp the same held true with the mullard cv4003's simply the best sounding..

Really?...I remember you and Badas once favoured 6BL7 tubes over 6AS7G/5998 family tubes.

Have things changed since?

 

[raindownthunda]

I have a used WE 421a tube I tried for the first time that sounded great for 5 min, but then a bright white spot developed in the middle of one of the plates and would flash but stay persistent. At the same time LOUD popping noises were heard. I quickly ripped off my headphones and powered down the amp. Luckily the headphones still work, but my ears are not happy.

Is this a sign the power tube is going bad?? I'm afraid to try it again and have a bit of PTSD now trying out tubes...

Going forward I think I will warm up the tubes before plugging in headphones. What is the minimum time I should wait before listening in case this happens again?

 

[AlexDDD]

I have a used WE 421a tube I tried for the first time that sounded great for 5 min, but then a bright white spot developed in the middle of one of the plates and would flash but stay persistent. At the same time LOUD popping noises were heard. I quickly ripped off my headphones and powered down the amp. Luckily the headphones still work, but my ears are not happy.

Is this a sign the power tube is going bad?? I'm afraid to try it again and have a bit of PTSD now trying out tubes...
Going forward I think I will warm up the tubes before plugging in headphones. What is the minimum time I should wait before listening in case this happens again?

I am afraid the tube will need to be replaced, it happened with my previous rectifier(the bright glow witch dissapeared in a couple of seconds but the sound got distorted and that was it)

 

[Wes S]

I am afraid the tube will need to be replaced, it happened with my previous rectifier(the bright glow witch dissapeared in a couple of seconds but the sound got distorted and that was it)

I concur. I would not put that tube back in my amp. Bummer it had to be the famous and expensive 421a!

 

[mordy]

I have a used WE 421a tube I tried for the first time that sounded great for 5 min, but then a bright white spot developed in the middle of one of the plates and would flash but stay persistent. At the same time LOUD popping noises were heard. I quickly ripped off my headphones and powered down the amp. Luckily the headphones still work, but my ears are not happy.

Is this a sign the power tube is going bad?? I'm afraid to try it again and have a bit of PTSD now trying out tubes...

Going forward I think I will warm up the tubes before plugging in headphones. What is the minimum time I should wait before listening in case this happens again?

It is always a good idea with a tube amp to turn it on and let it warm up for a couple of minutes without headphones.
Then test that everything is OK with a pair of
cheap sacrificial headphones just in case there are popping or explosive noises.
If you follow this protocol it is much less likely that you will blow a driver in your expensive headphones.
A little tedious, but better than replacing drivers in your headphones.

 

[raindownthunda]

It is always a good idea with a tube amp to turn it on and let it warm up for a couple of minutes without headphones.
Then test that everything is OK with a pair of
cheap sacrificial headphones just in case there are popping or explosive noises.
If you follow this protocol it is much less likely that you will blow a driver in your expensive headphones.
A little tedious, but better than replacing drivers in your headphones.

Good suggestions - I will do this going forward! How long should I warm the tube up with the cheapies before it is generally "safe" to listen to?

I had the same white spark + popping issue happen with a different tube that was supposed to have been tested in excellent condition... So it got me wondering if it had something to do with my amp (a brand new BHC build) and not the tubes.

I inspected my wiring & soldering work and noticed that after the flex of adding/removing a few output tubes, it looked like there were two red wires soldered to output pins ALMOST touching wire to wire (Pins 2 & 3). I was wondering if perhaps under the flex of changing tubes, the wires came close enough to crossing at the socket that would cause the tubes to pop/show bright lights, perhaps due to too much voltage??

Here is a pic I captured when the loud popping started happening. FWIW I think the popping was only out of the right channel...


I re-wired the output socket pin wires to be further apart to be sure they wouldn't come close to touching and reflowed a few ground joints around the headphone output. I'm trying out the same tube out and am 25 mins in and have the cheap headphones plugged in without any issues at all.

To be sure I can rule the tubes out... Once a tube is arcing does it keep arcing and get worse? Or can it be random and intermittent. I'm wondering if the output wiring was actually the culprit and not the tubes arcing.

 

[mordy]

Good suggestions - I will do this going forward! How long should I warm the tube up with the cheapies before it is generally "safe" to listen to?

I had the same white spark + popping issue happen with a different tube that was supposed to have been tested in excellent condition... So it got me wondering if it had something to do with my amp (a brand new BHC build) and not the tubes.

I inspected my wiring & soldering work and noticed that after the flex of adding/removing a few output tubes, it looked like there were two red wires soldered to output pins ALMOST touching wire to wire (Pins 2 & 3). I was wondering if perhaps under the flex of changing tubes, the wires came close enough to crossing at the socket that would cause the tubes to pop/show bright lights, perhaps due to too much voltage??

Here is a pic I captured when the loud popping started happening. FWIW I think the popping was only out of the right channel...


I re-wired the output socket pin wires to be further apart to be sure they wouldn't come close to touching and reflowed a few ground joints around the headphone output. I'm trying out the same tube out and am 25 mins in and have the cheap headphones plugged in without any issues at all.

To be sure I can rule the tubes out... Once a tube is arcing does it keep arcing and get worse? Or can it be random and intermittent. I'm wondering if the output wiring was actually the culprit and not the tubes arcing.

Others would have to weigh in on how long to leave the amp on when starting it up in order to avoid problems. Personally, I turn the amp on without any headphones plugged in for a minute or two. Then I plug in the cheap headphones for a couple of minutes. If no problems, plug in your favorite headphones....
Regarding your arcing problem I do not have the experience or knowledge to diagnose the problem. It occurs to me that there are several tube amp designers and builders on Head-Fi that should be able to tell you what the problem is.

 

[raindownthunda]

I was able to resolve the issue with the loud popping + bright white glowing dot on the plate. I found a short in pins 2 & 3 on the octal socket. According to Glenn this would cause the tube to draw too much current. Yikes!

Now to get this thread back on track, I found this ad for Bendix from an Electronics magazine vintage 1957 while researching the pair of Bendix 6080wb I just picked up. I wonder how much they cost in 1957? The amount of abuse these tubes were built to handle is pretty crazy!

From the standpoint of design features (see above), these reliable hard glass tubes
offer the superior quality needed to survive today's severe environmental demands.
Specifically, Bendix HY-G-300's are designed to withstand the following
environmental conditions-bulb temperatures up to 300° C; vibration up to
20G's over the range of 5-2000 cycles; and shock of 200G's having 20 -millisecond
duration.
For full information about the HY-G-300 line ... the surest answer to electron
tube applications in jet aircraft, missiles and rockets ... write RED BANK DIVISION,
BENDIX AVIATION CORPORATION, EATONTOWN, NEW JERSEY.

Source: https://www.americanradiohistory.com/Archive-Electronics/50s/Electronics-1957-08.pdf

 

[mordy]

Some of the 6080 type tubes and others were developed for military use in missiles and rockets. Perhaps the last application of tubes for military use before transistors took over was subminiature vacuum tubes:

The flying leads make them somewhat difficult to adopt to octal sockets but it is doable - they come as triods and dual triodes compatible with the 6SN7 tubes. The glass envelope is about 3/4" long or less, and these tubes are the ultimate in shock proofing and vibration resistance; some of them can withstand 500G and higher!
There are plenty of them available at very low prices.
Here is an interesting article:
https://www.effectrode.com/knowledge-base/subminiature-tubes/