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Old 10th Dec 2004, 6:19 pm   #1
Sam
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Default 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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Old 12th Dec 2004, 5:05 pm   #2
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Default 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.

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Old 12th Dec 2004, 6:42 pm   #3
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Default Re: Substituting the Evil Transistor

Don't forget ECL ( Emitter Coupled Logic (Motorola 1966))
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Old 12th Dec 2004, 8:02 pm   #4
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Default Re: Substituting the Evil Transistor

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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 " +.
AAAGGHHHH!!!! NORBITS! I remember them well - thumping great things (and typically British), they were carried in TV Centre stores until the mid-80s - some control system used them. I also recall some of the DTL stuff which was used in the BBC-designed comms. system. We had to keep boards back as these comms systems were scrapped to maintain a stock of the DTL - I also recall the 5V, 60A **LINEAR** PSU that powered it...

Wasn't the " device of choice " the E88CC in logic circuits?

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Old 12th Dec 2004, 8:54 pm   #5
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Default 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.
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Old 12th Dec 2004, 11:38 pm   #6
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Default 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.
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Old 13th Dec 2004, 9:51 am   #7
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Default Re: Substituting the Evil Transistor

I have a couple of Norbit devices. Imagine a DIL chip in your worst nighmares.
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Old 13th Dec 2004, 11:23 am   #8
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Default 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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Old 18th Dec 2004, 11:37 am   #9
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Default 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.

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Old 18th Dec 2004, 12:55 pm   #10
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Default Re: Substituting the Evil Transistor

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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
I thought that one of the big features of the Pegasus was that the cabinets were air conditioned which avoided the need for aircon in the room.
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Old 18th Dec 2004, 7:01 pm   #11
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Default 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.

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Old 26th Dec 2004, 4:33 pm   #12
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Default Re: Substituting the Evil Transistor

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Originally Posted by jim_beacon
ECL is still with iswith us - it is often used in the front end of high frequency counters and the like.
...and in an awful lot of digital video gear, where it's usually the interface between the serialiser/deserialisers and the rest of the circuit.
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Old 26th Dec 2004, 10:00 pm   #13
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Default Re: Substituting the Evil Transistor

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Originally Posted by mjizycky
...and in an awful lot of digital video gear, where it's usually the interface between the serialiser/deserialisers and the rest of the circuit.
Not any more Mike. The old Sony serialisers/deserialisers used ECL to interface to the rest of the system but they are obsolete.The final output to the co-ax is a sort of ECL and the interconnect between the newer (Gennum and National) equalisers and deserialisers is PECL (positive rail referenced ECL) but everything else is good old CMOS.

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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Old 21st Feb 2005, 2:03 am   #14
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Default 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.
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Old 22nd Feb 2005, 9:39 pm   #15
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Default Re: Substituting the Evil Transistor

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Originally Posted by adibrook
I think the old WWII decoding machine that used a few KW and filled a room could easily be replaced by a single chip.
That would be Colossus. It is the insparation behind my silly Thyratron Clock idea! I now have well over the 50-odd Thyratrons I need (bought another 38 2D21s from the states. They are pulls, and some of them say IBM on the side!), and a couple of Dekatrons for good measure. Now just to make the thing! (AND repair the 15 non-working radios I have, AND play with some of the logic circuits, AND finish my Triumph, AND service my R-to-R players, AND get a decent degree!)

Sam
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Old 22nd Feb 2005, 11:22 pm   #16
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Default 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.
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Old 22nd Feb 2005, 11:58 pm   #17
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Default Re: Substituting the Evil Transistor

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Originally Posted by SPCh
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 !
Don't worry, I know where my priorities lie. This is why I have 15 (or so) non-working radios, an assortment of components that may become a clock, and a classic Motorcycle that won't engage 1st gear!

Quote:
Originally Posted by SPCh
Go for the degree first, then play (for an employer) for 30 well-paid years or so, then retire
That was my plan: work until I don't have to any more, save up a nice load of cash, then spend it before any kids I have can inherit it!

Sam
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Old 23rd Feb 2005, 12:12 am   #18
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Default 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 !) ?
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