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RE: IIRC

Posted by unclestu (D) on June 13, 2015 at 16:46:44

In Reply to: RE: IIRC posted by DAK on June 12, 2015 at 21:20:54:

Don't think the military would use so expensive tubes in a missile which is an expendable device. The addressing of cathode poisoning was key for the early ENIAC and Colossus computers , which although they were powered on 24/7, not all of the 1500 to 2500 tubes would be used. Many would be powered up but simply idling. There are many other 6SN7's which have the extra mica and support rods.

Early versions had tremendous difficulty in both troubleshooting and tube failures.

Remember during WWII the military conducted many studies on tube life. They found that the more common the tube, the lower the failure rate, which is why the Red Base uses common types, not anything exotic. Cathode poisoning was not an issue as the tubes were limited in number and readily accessible.

True, long life tubes were important in Radar assemblies and stations which were also on 24/7.

100G capability was not really for missiles but more for US Navy ships which had to be able to endure shelling. You see this in 9 pin JAN tubes with their extra support rods, double thickness of mica, and extra "fingers" on the mica sheets.

The use of tubes drifted towards miniaturization, though. IIRC, 12AX7 gets introduced in 1954/1955. The 60's are dominated by the 9 pin miniatures. Even later, we get the nuvistors and then the truly miniature glass types which were directly soldered to the boards (VTV has an article about them too). IIRC they are still used on the Patriot anti missile missiles.

The current B 52's still use, IIRC, the 5R4WGB's, and their robust construction indicates the abuse they were intended to endure ( plus the high altitudes). The Russian 6C33 was found in that MG 21 which defected to Japan several decades ago. Highly immune to EMF, the US answer was better shielding.

Incidentally the HiPo 6S78 6SN7 that VTV tested came from my stocks

Edits: 06/13/15

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