Thermal event observed, need help

Peter W wrote:

Audio tubes produced today would be laughed right into the trash if foisted on the public 50 years ago.

A good reason to pay the freight and purchase such tubes as that GZ37 where possible, practical, and available.

Excuse me - but your blanket statement is incorrect IMHO and is insulting to people who use and enjoy current production tubes.

There is no current production tube directly comparable to the GZ37. But that doesn't mean all current tubes are "trash". And a good number are widely perceived to be sonicaly every bit as good or better than the old stock. The Genalex KT series power tubes come to mind as a good example.

There are also new production tubes that can really take a pounding - the EL84M Sovtek is just one example. The 6922 EH is another.

I believe you are doing a disservice to consumers of what is written here by making those statements.

Yes, the GZ37 is a hell of a tube. No, modern tubes are not all trash.

Jim McShane wrote:

Peter W wrote:

Audio tubes produced today would be laughed right into the trash if foisted on the public 50 years ago.

A good reason to pay the freight and purchase such tubes as that GZ37 where possible, practical, and available.

Excuse me - but your blanket statement is incorrect IMHO and is insulting to people who use and enjoy current production tubes.

There is no current production tube directly comparable to the GZ37. But that doesn't mean all current tubes are "trash". And a good number are widely perceived to be sonicaly every bit as good or better than the old stock. The Genalex KT series power tubes come to mind as a good example.

There are also new production tubes that can really take a pounding - the EL84M Sovtek is just one example. The 6922 EH is another.

I believe you are doing a disservice to consumers of what is written here by making those statements.

Yes, the GZ37 is a hell of a tube. No, modern tubes are not all trash.

Jim:

I gave myself some time to answer this.

Given my genuine respect for you as one of the few entirely ethical and legitimate tube purveyors on the planet today, and as an expert on the species, please understand my position. I will illustrate by two anecdotes first.

a) I have a Dynaco ST70 date-stamped 1963 that I have owned and used since the late 1990s. I purchased it from a private individual who retired from the record (as in vinyl) business. He purchased it as a kit, built it, and ran it 6 days per week in his store until he closed. Then, it sat in a closet for about 10 years before I purchased it at a house-sale. He was moving to points south. He claims it had the original tubes then (see below), and it has the same now. They test at 30+% over minimum on my Hickok 539B. They are within 6% for plate current as well. I would SWAG that those tubes have well over 30,000 hours on them. And still lots of getter-flash. Tubes are Siemens thin-man EL34s. Which suggest that they are replacements as they are not Dynaco-branded. So, I am splitting the difference between the 80,000+ hours that the pure math would support, and my use, and being conservative.

b) I have a Scott LK150 with all-GE 6550s. I traded for this device in 2004 from a collector in Michigan who lusted after a radio I had and had two of the above. He built it from-new, also in 1963, and replaced the OEM tubes in 1970 with the incumbents. He suggested about 20,000 hours, I have added about 10,000 hours. Those tube test about 20% over-minimum on the same tester, and are within 4% for plate current.

Now, there have been a LOT of complaints on recent-production Tung-Sol branded tubes.
Various other brands are getting mixed reviews.
Many here are experiencing short-life/multiple failures of various brands.

Those three actualities simply did not exist 'back in the day'. There was little to choose between branded tubes sold in branded boxes. Sure, IRC and off-brand tubes selling culls and seconds were a mixed bag, but when a box was marked RCA or GE or Tung-Sol or Mullard, or Telefunken, there was a near-certainty that it contained a good tube, well made, and with good longevity.

Not so much today. What is produced today would, very likely, turn up as seconds or culls by the majors. I was once in a Sylvania factory (no longer active, but the building it was in), that contained over 100,000 square feet on three floors in the main building, ran 24/7 at its peak and put out quite specifically millions of tubes in any given year, of hundreds of different types. That sort of broad and deep production simply does not happen today, nor does the level of quality control exist that would support such an endeavor. So, we get the bad Tung-Sols, and spotty quality elsewhere and so forth.

It is not that there are NO good tubes. But it is no longer possible to go down to the corner drug-store and be dead-certain that the tube purchased there would be a good one. As it once was.

If I might weigh in from the welterweight class ...
We as yet don't have the hours logged on the new-issue tubes to derive a meaningful comparison between their behaviours and the legendary longevity of post-war commercial tube production. How many people with a new VTA amp or Mottram pre-amp have actually logged 10k hours on the chassis tubes yet? My guess is it's a pretty small sample. I built my first VTAs in 2012 or '13 and i KNOW I haven't put that much time on them or their tube complements.
I doubt even Jim McShane would argue that QC is as consistent now in a modern tube factory as it was back in the New Jersey days. The tolerances were so good back then that hand tube-matching at the end-user end was hardly necessary. Not so, now, and this is where Jim rightfully makes his niche. However, does my inanimate amplifier give a rat's patootie where the output tubes were matched or by whom? No, it is not conscious of that -- only that they do match.
(And let us not forget that RCA made some real junk in its later tube production years as manufacturing was moved to South America to keep up with the diminishing demand for replacement tubes during the solid-state transition.)
Could you even make a decent Edison-grade Tung-Sol in the U.S. anymore? No, for two reasons. There's no labour pool, and the EPA would be on you like white on rice.
There is also the cost-benefit analysis. Let's say we "only" get 3k hours out of a modern Gold Lion KT-88 or equivalent TS-6550. From Jim in matched sets they go for ~$50 each. Or let's go with the original NOS GEC or New Jersey equivalents of those tubes which in this market cost upwards of $250 each but still be above failure readings at 10k hours. From that perspective, unless you're an purist or collector, the NOS tubes just ain't worth the money.
I was going to draw the line at signal tubes. Pretty damn hard to beat a good Sylvania, Mullard, Telefunken, Amperex or RCA at any price but then again, there are exceptions. I have had incredible delight using new Chinese CV-181s in 6SN7 holes. They're not cheap and how long they'll last, who knows? But when they're good, they're very, very good.

Nowadays just about everything is designed to fail. Back in the good old days most things were designed and built to last for as long as possible.

I imagine that the same goes for tubes. Now a days if a manufacturer wanted to build tubes to be as good as they used to be it would be very easy considering that virtually every facet of engineering and manufacturing is more advanced than it was 50 years ago. It has nothing to do with a reduced skill set of the assembly line person or inferior manufacturing techniques. Sure the components are made to be more fragile and when they suck the air out of the tube I bet they opened up the acceptable range for how many inches of mercury they need to pull...but that is all because of part of planned obsolescence.

And I'm sure there are exceptions to the rule. Automobiles being one exception.

Dogstar, I dunno about fragility in modern tubes.
I dropped one of McShane's GL KT-88s about 4 feet to a hardwood floor, striking the hi-fi cabinet (also hard wood) on its way down, and it went right back in the hole and still works.

I'm going to make this my final post in this thread, but there are some real misconceptions I want to just mention and see if I can clear a few things up.

First - anecdotal evidence is not of much value. There are lots of Russian tubes out there that have lasted a VERY long time as well. But a few cases does not mean that you can expect that behavior from all tubes of the type. Yes, I have customers who have seven years on their KT-88 Genalexes. But not all last that long - and some will last longer! A lot depends on the gear they are used in. BTW, my first set of KT-90 Ei tubes lasted 11 years, my 2nd set is going on 16 years. Real garbage, right?

Second- if tubes used to be so good in the old days why was it necessary for repairmen to carry so many with them as spares? People have this romanticized view of old stock tubes because the ones we see nowadays are survivors! The bad ones are all gone, used up or thrown away. Reliability has never been tubes' strong point. Yes, there is some abuse tubes just shrug off that would fry SS devices. But tubes DO wear out and sometimes do fail prematurely. They always have.

Third - I get very few complaints about Tung-Sol reissue tubes. Maybe someone else does - but not me. And I sell a lot of them.

Fourth - one poster wrote "Those three actualities simply did not exist 'back in the day'. There was little to choose between branded tubes sold in branded boxes. Sure, IRC and off-brand tubes selling culls and seconds were a mixed bag, but when a box was marked RCA or GE or Tung-Sol or Mullard, or Telefunken, there was a near-certainty that it contained a good tube, well made, and with good longevity." Hell, you couldn't even be sure the tube inside the box was even MADE by the company named on the box! LOTS of the old stock tubes were either rejected at the plant or sold off as seconds. A whole bunch of companies sprung up that specialized in selling rejects from the big tube factories.

Check out this picture:

Fifth - Tubes have been hand made devices for their entire existence - they were in the old days and they still are now. Tube manufacturing has NOT advanced much at all - it's still the skills of the line workers that means the most.

Sixth - I have sold well over 500 pieces of NOS GE JAN 6550A tubes over time (I don't have any now, sorry). The vast majority were sold in matched sets for audio or guitar amp service. When I ran the tubes to match them variances of as much as 100% in cathode current and 30% in transconductance were noted in significant numbers of tubes. GE 6550As were designed with input from Fender Amp R&D head Ed Jahns to be the power tube for the famous Fender 400-PS. That pedigree made it one of the most durable and highest quality power tubes of all time. But they varied significantly from sample to sample and matching was a must. There was even a special procedure developed for matching the tubes in the 400-PS! My experience with current production power tubes is that they exhibit about the same sample-to-sample variation as the old stock tubes did.

I once bought a lot of NOS RCA 12AX7s and had to return most of them - they had HUGE section-to section/triode-to-triode differences. I have some GE 7581As that vary over 200% in cathode current. I'll bet that of all the RCA 5V4GAs I've handled over 50% had badly tilted glass bottles. Yes, even old stock tubes had issues...

To close let me just say that without a doubt the old stock tubes had a number of wonderful attributes. And I would say at this point that current production tubes have not achieved the level of durability the good old stock stuff did (not all were so great - 50B5s used to cause fires(!), 7591s had an oscillation problem, 8417s were VERY hard to make right, etc.). But this worship of old stock is inappropriate and unfounded in MANY cases. In my opinion (and I'm far from alone in thinking this way!) the best of today's production work VERY well and compare favorably with the high quality tubes of the earlier days. Many here forget that I sold almost nothing but old stock for years - and many also know I won't sell what I wouldn't put in my own gear.

deepee99 wrote:Dogstar, I dunno about fragility in modern tubes.
I dropped one of McShane's GL KT-88s about 4 feet to a hardwood floor, striking the hi-fi cabinet (also hard wood) on its way down, and it went right back in the hole and still works.

The word 'fragile' was probably not the best word to describe the point I was trying to make. I bet if you dropped a similar tube 50 years ago it probably would have survived as well.

And I still can't think of a word to use to describe how tubes today are probably designed and manufactured to have a shorter life.

"And I still can't think of a word to use to describe how tubes today are probably designed and manufactured to have a shorter life."

The term you seek is "planned obsolescence". It describes the (nefarious, and supposedly conscious) practice of modern manufacturers to make shoddy merchandise which is predestined to fail within a certain period of time, so that the consumer is forced to re-buy. Hopefully in this scenario the heedless mark is stupid enough to buy the same unit again.
It is a controversial concept. And one which presupposes that stuff from the "Golden Age" of the fifties and sixties is truly superior.  It's an area of contention which has too many facets to argue here, but plainly one of the topics must be if  memory is selective and hazed over by nostalgia. "Let's Make Tubes Great Again". {insert orange-headed monster emoticon here}
Here's something to ponder: when I was young in that "Golden Era" the term "Made in Japan" was a term of derision. How things have changed!
Mr. McShane makes a very important point - in that Golden Age there were millions of tubes produced, and millions were sold. The major players could afford to overproduce, then cull. It didn't affect the bottom line significantly. What is the percentage of modern tube production to those peak years? 2 or 3% maybe, tops? The conclusions are obvious.

And here's a prediction: Chinese-made vacuum tubes will improve by leaps and bounds - it's already happening, it seems - and within five to ten years they will dominate the market. Karnac hath spoken.

Mr McShane is spot on!
Correct in facts, well formulated and leaves no doubts.

Dogstar wrote:

deepee99 wrote:Dogstar, I dunno about fragility in modern tubes.
I dropped one of McShane's GL KT-88s about 4 feet to a hardwood floor, striking the hi-fi cabinet (also hard wood) on its way down, and it went right back in the hole and still works.

The word 'fragile' was probably not the best word to describe the point I was trying to make. I bet if you dropped a similar tube 50 years ago it probably would have survived as well.

And I still can't think of a word to use to describe how tubes today are probably designed and manufactured to have a shorter life.

So I posted my reply before Jim McShane posted his reply. I based my response on the general state of engineering design and manufacturing for everything as a whole. To be honest I thought for sure automation is a part of tube manufacturing nowadays.

I was trying to avoid the term 'planned obsolescence' because it really does describe how the tube is different from tubes from 50 years ago.

As it seems we are finding out tube rolling may be the main reason tube life is relatively short. 50 years ago perhaps tube rolling wasn't a hobby. People had better things to do perhaps. like collecting and playing records.

The Tung Sol KT-120's I bought lasted perhaps 2000 hours which I though was a pretty long period of time. During that time I did move and I did remove and reinstall the tubes a few times. Maybe I was rough on the tubes.

In the time that I've had my first tube amp I've tried out only three different output tubes and to be honest even though there may be subtle differences I know the biggest differences in sound of course comes from the different speakers I have

Interesting discussion. I have been a product developer my entire  career working in R&D. Also in a disposable product area. So I know all too well that increasing the service life of a product is something that needs to be approached with caution given market realities. Simple math. If all of a sudden a product lasts longer your customer base wont need to buy as many. In turn manufacturing volume will decline at the factory, leading to higher unit mfg cost. (fixed overhead spread over less units) So not only putting pressure on the top line (gross volume) but at the same time on the bottom line (margins). Then wall street gets wind that volume and profitability is trending downwards and the stock price takes a beating!! Your Russian or Chinese tubes we may not always be talking publicly held companies but at least in the business world profit and loss drivers are basically a global constant.

Secondly the days of discarding product like shown in the picture Jim shared is a bygone era.  Although it is revealing of at least one of the factors responsible for the difference being debated, ie the intentional skewing of the product population. Old style thinking, funny how back then it was being touted as a positive. Nowadays advanced quality tools like 6 sigma and TQM dominate. In this respect the Chinese located mfg plants in the multinational I worked for were held to the exact same standard as our factories in the US or anywhere for that matter.  As a plant manager no matter where located better achieve and maintain excellent yields or you'll find yourself kicking stones down the road!

Finally is the question of raw materials. A lot of my time was spent either finding or developing replacements for things being added to the banned substances list that many countries are signatories to. No matter where made you cant legally import products it if it contains baddies like hexavalent chrome or asbestos and that list is getting longer all the time. But those old brake pads were oh so good!!! The substitutes for some reason never perform as well. I doubt tube manufactures are immune, in fact I'd bet quite the opposite.

So we are left with modern tubes for a modern world.

Off topic (or not) I find it odd that many medications and industrial compounds (refrigerants come to mind) become suddenly unhealthy the day after duPont's or Merck's patents expire . . .

deepee99 wrote:Off topic (or not) I find it odd that many medications and industrial compounds (refrigerants come to mind) become suddenly unhealthy the day after duPont's or Merck's patents expire . . .

You are such a rogue, never stop.

LeGrace makes some good points.

Back in the Golden Age of Vacuum Tubes, environmental controls hardly existed. It's difficult to imagine today that Sylvania would be allowed to discard mountains of unwanted tubes. And then there is the issue of banned substances and processes.

In my VTA-70, the four modern power tubes are from Sovtek, the three drivers and rectifier are NOS. Let's call it a tie, and move on to something else.

Note: The Russian tube factories are owned and/or controlled by New Sensor, an American corporation based in New York City.

Gregg R. wrote:LeGrace makes some good points.

Back in the Golden Age of Vacuum Tubes, environmental controls hardly existed. It's difficult to imagine today that Sylvania would be allowed to discard mountains of unwanted tubes. And then there is the issue of banned substances and processes.

In my VTA-70, the four modern power tubes are from Sovtek, the three drivers and rectifier are NOS. Let's call it a tie, and move on to something else.

Note: The Russian tube factories are owned and/or controlled by New Sensor, an American corporation based in New York City.

I'm with Greg R. Move along folks, nothing to see here. Exceptions might be rectifiers (the Mullard GZ-33) and certain small signal tubes; other NOS are more of value to collectors than they are to the end-user of these consumables. I mean, why collect something you can't use? Even with a stamp collection, you can always mail a letter with the buggers (unless they're cancelled, of course).

The EPA has driven a lot of useful activity such as tube construction overseas, mostly out of ignorance and without regard to the great strides in metallurgy, the handling of toxic metals, and economies of scale. But so long as we need good tubes for specific functions, someone will find a way to profitably build them. Even the Sovs and ChiComs have figured that one out, probably because there are more Bolsheviks in the EPA than in our former communist antagonists.

All that said, a genuine contribution to the art and science of tube gear would be finding a better way to connect the tubes to the circuit. It has always boggled me that this most critical connection in the circuit is the oldest, crudest and weakest. Maybe a small geared and serrated clamp on each pin that would cinch the buggers in place. . . the temptation has arisen more than once just to solder them in place, which is actually done in some micro-circuitry.

There is no dangerous materials in tubes, the manufacturing is also rather harmless. And tubes
are made in Europe, within EU .  Note that EU in some respects have the most stringent rules
for chemicals and environmental protection.

/*
Note that barium is poisonous , but the amounts in each tube is small, and
the handling at the factory can be done safe.

Directly heated tubes did contain thorium which is a rather weak alpha emitter,
but still classified as hazardous.
*/

Just closing the loop. The GZ37 that red plated soldiers on. tubes4ever knows his stuff. So right about not writing off the tube prematurely. My hope is the socket dressing addressed the issue. A red plate is not the end of the world after all. Will follow up in a couple months. Thanks for the assistance!

Well another month now of daily use and still no issues. The problem child M125 has been flawless ever since I reworked the rectifier socket and pounded down the one errant pin socket back into position. Not counting my chickens quite yet but confidence is increasing with each passing day.

LeGrace wrote:Well another month now of daily use and still no issues.  The problem child M125 has been flawless ever since I reworked the rectifier socket and pounded down the one errant pin socket back into position. Not counting my chickens quite yet but confidence is increasing with each passing day.

Not bad, matey. An errant B+ can drive one to drink, or marriage, or some other such nonsense.
Sounds like you've got 'er sussed. If you're that smart, you must really be from Quebec

This is an interesting thread, and hope this never happens to me. I chased a cold solder joint once in a dynavector P-75 phono stage, not fun.

Also interesting is the discussion about NOS tubes vs new production tubes.

I really don't have a comment on longevity, but I have been through signal tube rolling for sound, specifically 12AX7's, the 12AT7 family, and the 6922/7308/6DJ8 family. Mostly in a Manley Chinook phono stage and a McIntosh preamp C2200.

I would say that while new production tubes sounded OK, they're just OK, to me. I never found one in the above groups that sounded really good to me, in my system. Especially the 12AT7, I mean I tried a new production EH, shuguang, tung-sol, some other new prod tubes I don't remember, the newer nos mullard CV4024, an old triple mica black plate sylvania (was the best of the bunch), until I found some NOS Valvo blue label 6201's, maybe 1963 or so. Now there's a nice sounding tube, at least in the circuit I was using it in.

Anyway so while there may be nothing wrong with new production tubes as far as durability, etc., mostly for me the sound didn't quite cut it.

jfine wrote:This is an interesting thread, and hope this never happens to me. I chased a cold solder joint once in a dynavector P-75 phono stage, not fun.

Also interesting is the discussion about NOS tubes vs new production tubes.

I really don't have a comment on longevity, but I have been through signal tube rolling for sound, specifically 12AX7's, the 12AT7 family, and the 6922/7308/6DJ8 family. Mostly in a Manley Chinook phono stage and a McIntosh preamp C2200.

I would say that while new production tubes sounded OK, they're just OK, to me. I never found one in the above groups that sounded really good to me, in my system. Especially the 12AT7, I mean I tried a new production EH, shuguang, tung-sol, some other new prod tubes I don't remember, the newer nos mullard CV4024, an old triple mica black plate sylvania (was the best of the bunch), until I found some NOS Valvo blue label 6201's, maybe 1963 or so. Now there's a nice sounding tube, at least in the circuit I was using it in.

Anyway so while there may be nothing wrong with new production tubes as far as durability, etc., mostly for me the sound didn't quite cut it.

jfine, meant to get back to your comment earlier but couldn't find the thread. Also to whoever said that modern-day tube-rolling (whoever tube-rolled their old RCA round-screen CRT TVs?) was probably a new threat to tube longevity, short answer is, agreed with that.
I'm about to swap out a pair of relatively NOS Telefuken 12AT7s in my tube DAC for a new pair of PSVanes.The tubes in this Armani-priced DAC actually serve in a volt-amplifier, not the more common buffer role, so there should be (given burn-in, etc.) a change in audio performance. If I like 'em or can't tell the difference, I'll leave them in there and save the German tubes for a rainy day & report back.

deepee99 wrote:
I'm about to swap out a pair of relatively NOS Telefuken 12AT7s in my tube DAC for a new pair of PSVanes.The tubes in this Armani-priced DAC actually serve in a volt-amplifier, not the more common buffer role, so there should be (given burn-in, etc.) a change in audio performance. If I like 'em or can't tell the difference, I'll leave them in there and save the German tubes for a rainy day & report back.

Never liked the Telefunken 12AT7 much. Now the 12AX7 is a different story.

Gotta be ATs in this critter:
http://www.aquahifi.com/la_scala.html
Got any faves?

deepee99 wrote:Gotta be ATs in this critter:
http://www.aquahifi.com/la_scala.html
Got any faves?

Tubes - DAC
Tubes - DAC
Fish - Bicycle

Peter W. wrote:

deepee99 wrote:Gotta be ATs in this critter:
http://www.aquahifi.com/la_scala.html
Got any faves?

Tubes - DAC
Tubes - DAC
Fish - Bicycle

Peter, go burn a TV or something else worthwhile. Bicycles have feelings, too. A snowflake told me so . . . Ergo, so do DACs.