I had a conversation with a tube "expert" last night...

[tedmich]

EMP is a real threat, but they can harden equipment against it.

One of my biggest gripes with some movies (latest Godzilla comes to mind) is the fallacy of the reversible EMP.
"Oh the monster made an EMP and all our electronics are offline...but now they're back!" (!?)


it almost makes me as mad as when someone holds a lighter to a sprinkler head and every one on the whole floor magically goes off, perhaps via WiFi/Bluetooth.

https://youtu.be/uawAmbWoms0?t=1m35s

[Leo_Gnardo]

Ever microwave a CD? It's like a little miniature lightning storm.

Fun to microwave gummi bears too. Stand 'em up on a paper plate. Even better if the micro has a turntable to rotate the food. Saw this at a studio many years ago, couldn't stop laughing. Ever since then I've wanted to film it then run the film backwards. Too much good clean fun.

yes, EMP is a real threat, but they can harden equipment against it.

Besides hardening, backup systems. Hardening & shielding & backup reduce payload. If your plane can stay aloft, navigate & communicate with vacuum tube systems, so much the better. Less worry about "hardening, will it work?"

Yes Enzo we (and they, whoever they are) have shielding & "hardening" methods. Gazillions of $$$$$$$ spent research & development. Hope they never need to be tested under actual combat conditions, and if they do, hope they work. Cross your fingers for good luck, might help. Best to avoid nuclear war. Just one atomic blast can ruin your day.

OTOH you don't even need nuclear to produce EMP conditions now. Police were offered a system that could stop another vehicle's ignition system, useful in a car chase. What ever happened to that? First, aim isn't all that good, it can stop the cop car's ignition system too. Of course unless the cop car is "hardened", don't worry the citizens will pay... And the perp's car? That just becomes an unsteerable missile going how many MPH after the ignition quits. Mission scrubbed due to predictions of ancillary damage & death. Not just the perp's car but every other one nearby suddenly quit. Mayyyyybeeee not such a good idea...... NEXT!

About a year ago Boeing announced their flying EMP microwave attack jet. Such a tight aim it can switch off one building at a time. All well and good, I'm sure our military has some by now. Might come in handy, some situations. But if the enemy isn't dependent on power & hi tech devices to work, like da'esh/isis then not so much.

Need I mention that isis/da'esh or any disgruntled type could put together a microwave blaster & cause problems whenever & wherever they want. Doesn't take much of a budget, & nearly undetectable. Lights out! The next Unabomber won't have to blow anything up, just push a button to cut power & start mayhem.

[gui_tarzan]

Ever microwave a CD? It's like a little miniature lightning storm.

Yes I have! It's cool for about 5 seconds but it smells really, really bad when you open the door.

[teemuk]

But I sometimes wonder if the danger of an EMP event is exaggerated. When they were testing nukes near Las Vegas close enough to feel the ground shake did any electronics fail on the strip?

You can read about old nuclear tests. They did include research on effects of EMP.

The effects people seem to associate with EMP are far from "exaggerated". Things don't just "flash" for a second in neat Hollywood fashion and then stop working. The energy of the pulse actually freaks a lot of havoc. Soviet Union’s Test 124 performed in Kazakhstan in 1962 actually scorched several radios and a radar station 600 – 100 km from the detonation site. Arcs puncturing through windings wrecked several generators and transformers in the power grid. A 570 km long telephone line was measured to conduct thousands of amperes of current, which wrecked all the amplifiers, over voltage protectors and fuses in each and every repeater station along the line. Similarly massive current in an underground power line set an entire power plant in fire in Karanga.

Due to infancy and poor availability of semiconductor technology most of the wrecked equipment was actually based on vacuum tubes so overall their reliability statistics weren’t impressive. The infamous Starfish Prime tests performed by USA reputedly destroyed a lot of vacuum tube –based equipment as well. Tests also revealed that EMP currents were so massive that they would fry practically all passive components (resistors, caps, diodes, inductors, etc.) one would found inside a generic electronic device as well. If you had a tube radio chance is that it would just fry completely. Everything inside it. Everything.

Exaggerated?

[loudthud]

I was speaking of the idea that a single nuke detonated over Kansas or Nebraska would fry everything in the US coast to coast. That sounds more like someone padding their budget.

[cyclone]

I still have a Sovtek 50 watt head that runs the russian "5881" at 580 volts. tubes last years in that amp.

I have a white Bassman head with original Tungsol 5881's One stopped working, no filament In a moment of desperation, I reflowed the filament pin solder joints on the tube. voila!! Back in the amp it went.

I heard somewhere ( internet bs) once that the 5881 was designed for big radios that filled the back of a jeep, had to be rugged, hence the short envelope and lots of mica. Another supposed use was as a switch for the bomb bay doors on a B29.
After the russians captured one, they duplicated it to create the russian Bear bomber. Supposedly, they copied the 5881 to create the 6p3x tube for the identical function on their bomber.

[Leo_Gnardo]

I heard somewhere ( internet bs) once that the 5881 was designed for big radios that filled the back of a jeep, had to be rugged, hence the short envelope and lots of mica.

More likely, more spare 5881's than 6L6GA could be fit into scarce storage space on military vehicles that had radio transmitters. Plus 5881's are more rugged. Win-win. Of course that might be another myth. It's all hit or myth anyway.

[ThermionicScott]

More likely, more spare 5881's than 6L6GA could be fit into scarce storage space on military vehicles that had radio transmitters. Plus 5881's are more rugged. Win-win. Of course that might be another myth. It's all hit or myth anyway.

It was a case of "all of the above" for the 5881. The "bantam" 6V6GT was already about 12 years old when Tung-Sol introduced the 5881 in 1950, so the current 6L6GA was begging to be miniaturized next. The shorter elements helped with not only compactness but durability and microphony. And if you're going to the effort to improve a tube, you might as well give it a little more margin for dissipation and voltage ratings, as well as countermeasures against gas.

I have no doubt that lessons learned from rough treatment during WWII and concerns for use in Korea and the Cold War went into its development. Here's a link to Tung-Sol's original press release (see pages 3 and 4): http://www.pearl-hifi.com/06_Lit_Arc..._5881_Info.pdf

[Leo_Gnardo]

the current 6L6GA was begging to be miniaturized next.

As the 6L6GB? certainly seen some of those that looked & acted 'zackly like TS 5881.

[ThermionicScott]

As the 6L6GB? certainly seen some of those that looked & acted 'zackly like TS 5881.

I did some quick digging while composing my post and couldn't find much data on when the 6L6GB was introduced, except for a mention of "the early 1950s" which means the 5881 may have beaten it to the punch. The GB iteration tends to get short shrift in 6L6 history since it was only a repackaging of the earlier guts and not as sexy as the later 6L6GC.

(Of course, it's very probable that makers of 5881s and 6L6GCs later stuck those guts into bottles marked "6L6GB" for the replacement market since it let them satisfy multiple needs with fewer production lines.)

[teemuk]

The "bantam" 6V6GT was already about 12 years old when Tung-Sol introduced the 5881 in 1950, so the current 6L6GA was begging to be miniaturized next

We need to remember that 6L6 -based designs also evolved substantially throughout their history. The very first metal-enveloped 6L6 could dissipate only 19 watts and required plenty of ventilation to operate reliably. After introducing various versions of the design with glass envelope (which significantly improved cooling by radiation), the designers started to focus also on other modifications that could improve voltage handling and power dissipation ratings: mica base plates, thicker grid wires, cooling fins and black surface textures of the internal elements. With select modifications power dissipation ratings of these 6L6 tube variations (e.g. 5881) were gradually increased. The 6L6GC, for example, was rated for 30 watts. I recall 5881 had a somewhat lower figure. Something between original 6L6 and the more efficient later versions that followed. Pretty sure that in "W" versions the designers also focused on making the design mechanically rigid and sturdy because those were aimed for critical applications like aviation or military.

[ThermionicScott]

We need to remember that 6L6 -based designs also evolved substantially throughout their history. The very first metal-enveloped 6L6 could dissipate only 19 watts and required plenty of ventilation to operate reliably. After introducing various versions of the design with glass envelope (which significantly improved cooling by radiation), the designers started to focus also on other modifications that could improve voltage handling and power dissipation ratings: mica base plates, thicker grid wires, cooling fins and black surface textures of the internal elements. With select modifications power dissipation ratings of these 6L6 tube variations (e.g. 5881) were gradually increased. The 6L6GC, for example, was rated for 30 watts. I recall 5881 had a somewhat lower figure. Something between original 6L6 and the more efficient later versions that followed. Pretty sure that in "W" versions the designers also focused on making the design mechanically rigid and sturdy because those were aimed for critical applications like aviation or military.

Yep, I certainly haven't forgotten -- the 5881 just represents an intermediate step in that evolution. If my understanding is correct, the "6L6WGB" moniker was just another name for the 5881, used to emphasize that it was a rugged and compact substitute for the 6L6.

[pdf64]

If my understanding is correct, the "6L6WGB" moniker was just another name for the 5881

I thought that too, but just noticed that the TS 6L6WGB info lists its limiting screen grid voltage at 300, whereas it's 400 for the TS and RCA 5881.
http://www.mif.pg.gda.pl/homepages/f...7/6/6L6WGB.pdf Oct 55
http://www.mif.pg.gda.pl/homepages/f...049/5/5881.pdf 2-57
http://www.mif.pg.gda.pl/homepages/f...127/5/5881.pdf Jun 62

[Leo_Gnardo]

If my understanding is correct, the "6L6WGB" moniker was just another name for the 5881, used to emphasize that it was a rugged and compact substitute for the 6L6.

The ones that I've seen - real 6L6GB or WGB correspond to that description.

Of course NOT the ones marked GB or WGB by Groove or other merchandisers of phoney baloney, those often 6P3 Russki's or their China copies.

[ThermionicScott]

I thought that too, but just noticed that the TS 6L6WGB info lists its limiting screen grid voltage at 300, whereas it's 400 for the TS and RCA 5881.
http://www.mif.pg.gda.pl/homepages/f...7/6/6L6WGB.pdf Oct 55
http://www.mif.pg.gda.pl/homepages/f...049/5/5881.pdf 2-57
http://www.mif.pg.gda.pl/homepages/f...127/5/5881.pdf Jun 62

You're right, and that is a little perplexing -- why would TS bother to make a partially-uprated tube alongside its superior 5881? Would it be a slightly cheaper option? Perhaps (and I'm going off of no direct evidence here) they were in fact the same tube, but the screens were derated to meet the altitude/acceleration specs that are unique to the 6L6WGB itself: when the screens are hot (and have the potential to temporarily get really hot thanks to high screen voltages) they are much more susceptible to damage from shock. Just a theory, and I'd welcome authoritative correction.

The ones that I've seen - real 6L6GB or WGB correspond to that description.

Of course NOT the ones marked GB or WGB by Groove or other merchandisers of phoney baloney, those often 6P3 Russki's or their China copies.

Right. I'd kinda forgotten that the OP was asking about Russian "who knows what's inside" tubes by this point.