Subject:
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Re: Electronic brick (1968) schematics?
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Newsgroups:
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lugnet.trains
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Date:
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Tue, 13 Apr 2010 20:41:23 GMT
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Viewed:
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22990 times
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In lugnet.trains, Stefan Gustavson wrote:
> Several people here on Lugnet own copies of 139 (the 4.5V Electronic
> train control unit), and even though I am not quite eager enough
> to try to acquire a copy for myself, I'm still very much interested
> in this set, as it was a childhood dream of mine to own one.
> I still have the 1968 leaflet that advertised it to drool over.
>
> Has anyone ever tried to figure out its schematics? From the pictures
> of the electronic block, I can see that the circuit board is pretty
> clearly visible through the plastic casing, and even though the view
> is obstructed by studs, it should be possible to peek between them and
> make out all the components and their connections by looking through
> the plastic from several angles, without opening the brick (which I
> assume is glued together). There doesn't seem to be a whole lot of
> components in there, and it's 1960's technology with only discrete
> transistors, so the task is at least manageable.
>
> Does anyone have a schematic, or a set of close-up photos so that I
> can at least deduce the general amount and type of components?
> What images I have found on the net are of too low resolution.
> The exact circuit is probably difficult to reproduce without the
> antiquated germanium transistors from the era. (I do have a few in
> my scrap drawers, but probably not enough and of the right types.)
> However, a general grip on how many components there are, plus what
> types they are and their general placement, would make it easier
> for me to recreate a work-alike for the circuit and at least pretend
> I own one. I would of course also place the schematics on the net
> if I do manage to make a working replica.
>
> I could simply design a circuit from scratch, but it wouldn't be
> the same. I would very much like to copy the actual historic design,
> or at least borrow some contemporary design principles from it.
>
> Note that I would like to recreate the 139 with its "forward-stop-
> reverse-stop" logic, not the 138 ("go-stop") which would be pretty
> simple in comparison. I expect a lot fewer components were required
> for that first product.
>
> And last but not least, could someone record the sound of the whistle
> and post it somewhere or e-mail it to me, or just tell me what pitch it
> has (e.g by using a guitar tuner or similar), so that my re-make of
> the circuit can be compatible with the real thing? A suitable e-mail
> address for sending me a sound sample is "stefan.gustavson@gmail.com".
>
> Stefan Gustavson (#2407)
I've recently reverse-engineered the earlier unit from the 118 train set:
Circuit: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=4433934
Info:
http://www.brickshelf.com/gallery/mbellis/Trains/Electronics/set_118_vs_138_info.txt
Folder: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=161393
I would gladly do the same with a 139 unit if someone has one open.
If anyone has a 139 unit but does not want to open it, please could they post
the serial number from the top of the 14-pin IC? A torch may be useful to help
see it clearly.
I suspect it's TTL gates or flip-flops, which would yield a 4-digit number
beginning "74", or maybe a transistor array or an amplifier.
Most of the same electrolytic capacitors as the 118 unit are there, and at least
one of the others (the stripey ones).
Certainly there's an H-bridge of transistors in the 139 unit, to do the
bidirectional output, compared to the single larger transistor of the 118 unit.
It might be fun to interface this system with the Power Functions system. I
heard some people were finding IR interference from adjacent layouts at shows,
so maybe a revival of whistle-operation is a way round it ;-)
It should be easy enough to make a circuit to produce the whistle frequency.
Maybe a 555 timer circuit to make a 12-20kHz square wave, with a low-pass filter
to take the edges off the waveform. I'll have to try it sometime.
Then again, a whistle sound sample could now be downloaded to an NXT!
Mark
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Message is in Reply To:
 | | Electronic brick (1968) schematics?
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| Several people here on Lugnet own copies of 139 (the 4.5V Electronic train control unit), and even though I am not quite eager enough to try to acquire a copy for myself, I'm still very much interested in this set, as it was a childhood dream of (...) (17 years ago, 19-Jul-07, to lugnet.trains)
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