5963 computer grade dual triode production dates 3495

Yes, it does! I witnessed this happen one time which resulted in an supervisor earning a little unpaid vacation time.

Old multiplex equipment buttociated with Types J, K and L carrier systems used by AT&T's various companies built in the '40s and '50s used basically two tubes...the 311B triode, and the 310A sharp cutoff pentode, essentially a five prong, 5 V filament 6C6, for anything below the mastergroup MUX level. Above that, the 404A (basically a 5V 6AK5) and the 417A single triode were used for mastergroup gain and stacking. One day, a migration to IC-based equipment on another floor occurred in our office, the largest carrier office in the US, rendering an entire floor's worth of antique channel modems, group demods, supergroup demods and all buttociated equipment such as carrier supplies to be relegated to "spare" status. A transmission man working that floor, trying to earn a few "brownie" points, disconnected all the -24V filament battery at the BDFB to all this gear. Laziness and timidity precluded him from removing the +130 and +315 plate supplies. Thus, over 750 311B and 310A tubes were left in situ with their usual B+ on the plates and cold filaments.

About three months later, a surge in traffic demand prompted the circuit provision bureau to rebuttign new multiplex facilities to this equipment, and within a short lead time. When such work happens, the "circuit order" worker tests the gear both directions, sets levels as appropriate and checks for basic transmission impediments. In this case, the equipment didn't pbutt tone anywhere and wouldn't mod or demod anything at all, and a trip to the BDFB found boxes of 1 1-3 amp grbutthopper fuses all placed neatly on the floor in front of the fuse bay. After replacing all the filament supply fuses, the equipment still failed, but some of it would pbutt modulated-demodulated signal, but at bad levels and with not nearly enough gain to meet specifications. After some checking, they called me down to try to figure what happened.

Western Electric gear from that era used an "in service" tube test regimen that looked basically at plate and filament current and "filament activity" (an old term that really meant "cathode activity" in anything other than direct heated tubes.) The in service tests showed acceptable filament current, but the plate current was either gone or very weak. In cases where there was at least some plate current, dropping the filament current 10% wouldn't cause a dip in the plate current...odd. A trip to the Hickok Cardmatic (KS version, of course) showed all the tubes on the entire floor to be "dead" for Gm. That's when the "brownie" said, "Oh...well, I took all the filament fuses out of everything to save power. I reported it to my boss, and he put an attaboy in my folder." A little investigation proved this to be true, and the supervisor was given some time off for being an idiot. A look at the Bell System Practices relating to vacuum tubes specifically stated that at no time should any tube of any configuration, except for cold cathode tubes, be allowed to stand with B+ on any element without the filament being hot.

Some further investigation with the folks at the Littleton, CO WECO tube plant confirmed that running any tube with the plates energized and no filament will cause the same, or worse, symptoms as "sleeping sickness" generally attributed to having a tube run in cutoff for long periods of time. In short, what happens in either case of "sleeping sickness" is that the plate winds up acting as a getter, thus becoming unreceptive to electron reception from the cathode after being plated with contaminents within the envelope. That explained immediately why the tubes, while testing bad for Gm, tested good for cathode activity. This was further confirmed by the fact that newer tubes were still at least conducting something, while tubes that were some 30-40 years old were completely dead on test, although the records showed their last "in service" current test to be well within specs. Conversations with retiring engineers at the tube plant confirmed that no "real life" vacuum tube had a very good vacuum in it, and even if it had one, it would be partially destroyed during the initial aging process by gasification of the tungsten on the filament and thorium from the hot plates. That's why tubes have getters in them, after all. As the fellow told me, "You cut off electron flow, and that plate makes a really attractive getter...the higher the B+, the more it "gets!" Add to this that the cathode, grids and filaments are all at or near ground potential, and you see how this can happen to the plates.

In the final tally for this goof, over 350 310A tubes, at $150 a pop, and 200 some odd 311Bs, at $75 a pop, had to be replaced on an emergency basis. At the time, Western Electric was getting out of tube manufacturing altogether, and the buttembly and aging lines for the old ST envelope tubes were out of commission while the equipment was being sold to Richardson Electronics. As it turned out, a canvbutt of toll offices across the country had to be done to mine every available 310A and 311B, even old "pulls" from retired equipment, to get the MUX gear back into service. As it was, the due date for the facility additions was jeopardized by over two months, and the carrier group responsible for the gear (ours) had to buy all new Richardson tubes for the offices which gave up their spares. Total cost of the fiasco: over $130,000. There was little solace in the fact that the removal of the filament battery saved about $500 in power costs. To add insult to injury, the equipment only carried the service for another six months before being finally retired and scrapped.

"Audiophools" worrying about "cathode stripping" has nothing whatever to do with "sleeping sickness." I've yet to see any "audiophool" who actually knows how a tube works, anyway. You have to expect this from people who refer to audio phenomina as "air," "stage," "detail," "crispness" and other buttorted laughable terms.

dB

Sidebar: On that particular floor resided many old pieces of gear from the 1930s, including bays of voice order wire equipment buttociated with long gone J and K carrier systems. In them were rows of bayonet based 101D triodes and 201As, most dating from the 1930s, some from the '40s. All tested good when pulled after 45+ years of continuous service. I shudder to think what these old things would've brought today on fraudBay. The secret to long tube life at the phone company? Running filaments 10% below rated voltage and excellent quality elements. The Richardson replacements which came later were nowhere near the quality of any old WECO tube, and WECO tubes made in the early '80s were almost as bad.