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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment. |
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10th Dec 2004, 6:19 pm | #1 |
Hexode
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Substituting the Evil Transistor
As most of you are realising, I am developing unnatural interests for valves being used in circuitry they are not supposed to be! (my Thyratron Clock, for instance).
My latest musing is for logic circuits (I really should stick to one silly idea, rather than flit about between silly ideas!). I have found a lonely looking book tucked away in thr Uni Library on Counting and Transistor Logic. Now to the point. The diode logic I can easily work out how to use a thermionic diode, but the Transistor-Resistor Logic is not so easy, now I have thought about it. I did just think wherever it says 'transistor', read 'triode', but would a pentode be a better thing to use? The Ia/Va characteristic of a pentode having a similar shape to the Ic/Vce characteristic of the transistor. See what happens if I am given time to think about things! I should know better than to let myself muse over my idiotic notions! Sam
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12th Dec 2004, 5:05 pm | #2 |
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Re: Substituting the Evil Transistor
Hi Sam, most logic was used in a digital manner, i.e. either ON or Off, so the characteristic curve was not too important as long as the devices could be swithched on and off without too much power being used and reasonably quickly. We had DTL, RTL and TTL in the beginning (diode transistor, resistor transistor then transistor transistor logic). There were even a series of hybrid logic circuits produced by Mullard called NOR BIT, basically RTL but in a DIL package with a " leg " spacing of 1 " +. Let me know if you want some of the background info.
Ed |
12th Dec 2004, 6:42 pm | #3 |
Octode
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Re: Substituting the Evil Transistor
Don't forget ECL ( Emitter Coupled Logic (Motorola 1966))
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Chris |
12th Dec 2004, 8:02 pm | #4 | |
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Re: Substituting the Evil Transistor
Quote:
Wasn't the " device of choice " the E88CC in logic circuits? Last edited by Paul Stenning; 29th Dec 2004 at 11:22 am. |
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12th Dec 2004, 8:54 pm | #5 |
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Re: Substituting the Evil Transistor
ECL is still with iswith us - it is often used in the front end of high frequency counters and the like.
I have a few Philbrick analogue computer valve op-amps somewhere (two ECC83's on an octal plug-in unit). Jim. |
12th Dec 2004, 11:38 pm | #6 |
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Re: Substituting the Evil Transistor
Sam,
I'vefound a bit on flip-flops in an old Tektronix theory book I have. I'll try and post it somewhere later in the week. Jim. |
13th Dec 2004, 9:51 am | #7 |
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Re: Substituting the Evil Transistor
I have a couple of Norbit devices. Imagine a DIL chip in your worst nighmares.
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13th Dec 2004, 11:23 am | #8 |
Hexode
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Re: Substituting the Evil Transistor
Thanks for all of this! It was just an 'I'll see what other people think' sort of post!
I have copied down circuits for a Thyratron and Valve Flip-Flop, and there are some more in a book I have got out of the library. I think I will sit down after term has finished, and try and follow the circuits through when in its different states. If nothing else, it will keep me occupied until Dad can come and collect me! Wonder why logic couldn't interest me when had to do it last year? I think I will go with old metal-cased pentodes when/if I experiment with the logic circuits. Its only because I have a few of the same type in a box somewhere! Sam
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18th Dec 2004, 11:37 am | #9 |
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Re: Substituting the Evil Transistor
Hi Sam
Most of the old valve logic stuff used double triodes, typically E88CC which were rugged ECC88 (gold plated pins etc) & were basically two amplifiers, DC coupled so that if one was in " saturation " the other was cut off. DC design could be managed easily with Ohm's Law although AC performance, ie switching speed was a bit more difficult to predict. Its worth remembering two things; one is power consumption. When I was at college we had a Ferranti Pegasus. I think that the room was air conditioned - it had to be or it would have been pretty uncomfortable in there. The other thing is size. My first job was with a division of Elliott Automation and on several scrap heaps were bits of old Elliott valve computers. The boards were about A5 size and each contained two flip-flops! Elliotts also produced RTL logic " ICs " called Minilogs - about the size of Norbits but twice as thick. Joe |
18th Dec 2004, 12:55 pm | #10 | |
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Re: Substituting the Evil Transistor
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18th Dec 2004, 7:01 pm | #11 |
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Re: Substituting the Evil Transistor
Jeffery
You may well be right. It was so long ago that I even had a head of hair in those day! Joe. |
26th Dec 2004, 4:33 pm | #12 | |
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Re: Substituting the Evil Transistor
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26th Dec 2004, 10:00 pm | #13 | |
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Re: Substituting the Evil Transistor
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I think this is straying rather OT. If we want to continue in this direction I reckon it's worth a new topic. Something like "History of logic families"? |
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21st Feb 2005, 2:03 am | #14 |
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Re: Substituting the Evil Transistor
I suppsoe technically you could build any IC out of valves...i mean i think most ICs dont even use normal trannys, they use fets, which are actually closer in operation to valves. (?)
Size would be a problem tho ) I think the old WWII decoding machine that used a few KW and filled a room could easily be replaced by a single chip. |
22nd Feb 2005, 9:39 pm | #15 | |
Hexode
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Re: Substituting the Evil Transistor
Quote:
Sam
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22nd Feb 2005, 11:22 pm | #16 |
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Re: Substituting the Evil Transistor
Don't want to be a killjoy, Sam, but if you're after a degree you had really better shift it up the priority table just a bit ! Bad news, I know, but 45 years ago I was in the same position. Go for the degree first, then play (for an employer) for 30 well-paid years or so, then retire (you probably won't have the option by 2040) and play to your heart's content (like many of us, I suspect !) on a good pension. It's wonderfully liberating to be able to comfortably afford your indulgences. Good luck.
As Aeneas said to his troops "One day, even these things will be a pleasure to remember". No fool, Aeneas. |
22nd Feb 2005, 11:58 pm | #17 | ||
Hexode
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Re: Substituting the Evil Transistor
Quote:
Quote:
Sam
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23rd Feb 2005, 12:12 am | #18 |
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Re: Substituting the Evil Transistor
Okay, Sam.
Clearly you don't need any advice from me. Don't know what degree you're taking but, if it helps, E=2ZNPΦ/60C How's that after 40 years (but don't ask me what all the letters stand for !) ? |