CRfriend - Why the Pentode?

[jamie001]

I have been wondering why your posts display a pentode? I am an EE and was exposed to a small amount of vacuum tube theory in school, but the emphasis was primarily on transistors and op-amps. This was during the late 70's and early 80's. Do you have an affinity for vacuum tubes? Just curious...

Regards,

Jamie

[crfriend]

Jamie -- All my early dabblings in electronics were on tube gear, and I still have an affinity for the old technology. I keep hoping to find a small (ish) tube-based computer along the lines of a G-15 to merge the two passions.

[AMM]

IIRC (it's been a while), tube-based computers tended to use triodes (usually twin triodes), not pentodes. I seem to recall once seeing a board the size of a dining-room table with an array of miniature tubes, all twin triodes as far as I could tell.

Does that agree with your recollection?

[crfriend]

IIRC (it's been a while), tube-based computers tended to use triodes (usually twin triodes), not pentodes. [...] Does that agree with your recollection?

That squares completely with most of the documentation I've seen on tube computers, and in the later years specialised tubes were developed for computers that didn't suffer from some of the effects that "analogue" tubes (or. more precisely, those designed for such applications) suffered from.

However, as I mentioned, my earliest dabblings were in radio and television applications, so I'm familiar with the form. And, besides, it looks cool. (Beyond that, it warms my heart that "empty state" technology is still known to some.)

I'd not use firebottles in any new application, but in their setting they were the best tool for the job. That said, I happen to know a chap who just a few years ago did a modern 12-bit computer using tubes -- the MUNIAC. It's an interesting design.

[flarob]

Should you ever be in Philly, stop in to the Univ of Pennsylvania and visit the museum which houses the orig ENIAC puter. 100% tubes

[Brandy]

Try here also;
http://www.computerhistory.org/

-- Brandy

[crfriend]

Flarob -- Thanks for the tip. They don't have the entire machine (they can't, pieces of it are in several museums), but may have a larger chunk than anybody else. It might be worth a visit; I've never spent any time in Philadelphia save for passing through on the train.

Brandy -- The core of the collection at The Computer History Center came from the long-defunct Boston Computer Museum. That enterprise closed down in the mid 1990s having turned into more of a children's museum (which was right next door: location, location, location) than a preservation and stewardship institution. My group was quite possibly the last to actually see the historic collection before it was all shipped west. I remain bitter about that to this day, but the new folks seem to be working much harder at it than the original folks (I am not going to name names), and that bodes well; I really wish them luck.

[flarob]

You are right about pieces of it being in a few different places. It was developed there at the univ during the 2nd war. I dont remember if it was completed to actually be of any value during the war. I do know it took a ton of power to run it and they had a terrible time keeping all good tubes operating all the time. When I was going to Univ in philly for EE we took a tour of the puter ( 1960) LOL. Most of our theory at that time was tube, as transistor was very new at the time.