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Old 22nd Mar 2021, 8:32 pm   #101
Timbucus
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Default Re: The Transam Triton Personal Computer

The recommended one was a George Risk keyboard model 756 - which used a custom version of the KR2376 (-012) so the Factory ROM on the controller is unique to that model KB. The Chip is a single 5v rail so not sure why it needed -12v - maybe so others of the time could do so.

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I can't seem to find any info on that obscure Keyboard controller / encoder IC. I wonder if it's equivalent to a more stand AY-x-xxxx one or whether it's a custom microcontroller etc.
And the keyboard itself is now rather uncommon - do you have any documentation that came with it? - All I can find is:
https://deskthority.net/wiki/Micro_Switch_SD_Series
No I don't have any doc's, the hall effect switches work they give a pulse when you hit the keys, they are powered with +5v, so I wonder why you need the -12v
I presume it must have originally come with some data, for knowing how to connect the keyboard you had to it. They don't seem to specify what Keyboard they originally used was - but I assume it needed -12V if they put iit on the connector
And yours also needs this too, if your're measuring -12V on data lines (luckily buffered on board, so might help prevent too much damage)

I assume that, like the 8080, many PMOS devices back then needed extra rails, besides +5V, and the 'Keyboard Encoder' IC on your keyboard needed this (Although -12V is a bit off, as most only needed +12V / -5V).
-12V was usually only required (along with +12V) for RS232 etc.
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Old 22nd Mar 2021, 8:36 pm   #102
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Default Re: The Transam Triton Personal Computer

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I'm wondering if Tim might be able to consider testing the VDU IC as he has a working system? Some component suppliers, including some quite well known ones, have a habit of advertising ICs they don't actually have and only try to find them when anyone takes an interest.
I suppose I could do that without too much risk as Gerald seems to find that they are all just low as long as it does not have a dead short Vcc 5v to Ground as obviously mine is a standard Triton PSU without any luxuries of protection against shorts...
I am going to order one from littlediode as I am sure its dead, but before I do I want to check which version they have. Tim you said its need to be the A version SFF96364A on their site they don't specify. I give them a call tomorrow, they are not too far from me so may be I could go and pick one up.
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Old 22nd Mar 2021, 9:12 pm   #103
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Default Re: The Transam Triton Personal Computer

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I'm wondering if Tim might be able to consider testing the VDU IC as he has a working system? Some component suppliers, including some quite well known ones, have a habit of advertising ICs they don't actually have and only try to find them when anyone takes an interest.
I suppose I could do that without too much risk as Gerald seems to find that they are all just low as long as it does not have a dead short Vcc 5v to Ground as obviously mine is a standard Triton PSU without any luxuries of protection against shorts...
I am going to order one from littlediode as I am sure its dead, but before I do I want to check which version they have. Tim you said its need to be the A version SFF96364A on their site they don't specify. I give them a call tomorrow, they are not too far from me so may be I could go and pick one up.
I had mine from them so it was certainly an A model for me but, things change.
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Old 22nd Mar 2021, 9:21 pm   #104
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Default Re: The Transam Triton Personal Computer

AY-5-2376 used +5v and -12v. Maybe there were later versions that were 5v only.

http://telcontar.net/KBK/General_Ins...ifications.pdf
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Old 22nd Mar 2021, 9:30 pm   #105
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Default Re: The Transam Triton Personal Computer

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AY-5-2376 used +5v and -12v. Maybe there were later versions that were 5v only.

http://telcontar.net/KBK/General_Ins...ifications.pdf
Thanks for the correction Mark - I looked at the data sheet too quickly - the KR variant has the -12v as well on Pin 18
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Old 22nd Mar 2021, 11:28 pm   #106
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Default Re: The Transam Triton Personal Computer

Done a bit more research on my Keyboard the Model number is 84SD12-2 did not find any reference to that.

Its not a matrix scan keyboard, https://telcontar.net/KBK/tech/Hall_effect its Two-of-N encoding each switch has two open open collector outputs, some pulse like the letter and number keys but the Shift and Caps Lock stay low as long as you hold the key down.

So it part or the Micro Switch SD range https://telcontar.net/KBK/Micro_Switch/SD_keyboards date code is 77/39.

I think the 40pin chip on it is a custom rom so that not getting fixed anytime soon.
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Old 23rd Mar 2021, 12:50 am   #107
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Default Re: The Transam Triton Personal Computer

I'd recently being looking for an alternative to the AY-3-4592 single +5V rail 128/112 key 16/15 x 8 matrix (needs external De-mux) Capacitive keyboard encoder, used by Acorn System, as it's now very expensive.

And found these (that also require -12V) standard non-capacitive possibilities to design keyboard PCB:

AY-5-2376 / KR2376 88-key 11x8 matrix


AY-5-3600 90-key 10x9 matrix (Were 5off for $13 on an online auction site, but I then discovered I had one already) / KR3600

AY-5-3600PRO PROM / EPROM version, that can be programmed in Factory / Field for custom output codes
(I found Aliexpress seller had the at 99p+delivery)

The number at the end of the part is the ROM-size in bits, and they were in the ROM-Memory section of the GI Databook. And the higher number ones generally support more keys.


Whilst they all tend to give out a standard ASCII code for each key, the matrix arrangement is custom to the particular IC.
So not easy to swap from one IC to another, if keyboard matrix X or Y values are different, and each one requires a particular keyboard layout circuit / PCB

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Old 23rd Mar 2021, 10:29 am   #108
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Default Re: The Transam Triton Personal Computer

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Done a bit more research on my Keyboard the Model number is 84SD12-2 did not find any reference to that.

Its not a matrix scan keyboard, https://telcontar.net/KBK/tech/Hall_effect its Two-of-N encoding each switch has two open open collector outputs, some pulse like the letter and number keys but the Shift and Caps Lock stay low as long as you hold the key down.

So it part or the Micro Switch SD range https://telcontar.net/KBK/Micro_Switch/SD_keyboards date code is 77/39.

I think the 40pin chip on it is a custom rom so that not getting fixed anytime soon.

That's useful further info on it - I had assumed it might be an SD-16132, that was on the PCB photo you'd posted.

I'd not looked into Hall-effect key switches and that because they used single-ended outputs, you couldn't use a standard matrix-scanning IC.
But with these, each key effectively gives it's position by ground the relevant Row & Column key 'scan' matrix lines. So it actually simplifies the controller IC slightly and mainly just needs to be a ROM code converter of what codes are being presented to it from the keyswitches (plus some debouncing? & shift key handling).

After reading your links, I did a quick Google for Hall-effect Keyboard encoders and co-incidentally it found another page on that site: https://telcontar.net/KBK/tech/encoder_ICs

Where it summarises many of the standard scanned-matrix ones and does mention substitution of custom-ROM types (giving link to Acorn Stardot forum discussion), plus lists two 2-of-N for Dual-Output Hall effect switches:

Model Manufacturer Keys Modes Bits/key Output Coding Notes

MM5745 National 78 4 10 Parallel Custom
MM5746 Semiconductor 78 4 9 Parallell Custom

2-of-13 input (non-matrix); listed as 2KRO/NKRO but no explanation is given regarding how NKRO works without matrix scanning


So their might be some possibility of using one of those, if available.

I saw from another previous post "The recommended one was a George Risk keyboard model 756 - which used a custom version of the KR2376 (-012) so the Factory ROM on the controller is unique to that model KB"

So I presume your Keyboard must have used the same output codes (/ ASCII is standard) for most keys, in order for it to work on the Triton's firmware (Unless you had a special version of the Triton firmware for your keyboard's ROM-codes).
And so can probably find out what the ROM codes were, from people who have a working system / look at Triton's O/S code (A commented disassembly may be useful, to save some work).
An AVR etc. microcontroller could then be used to replicate the original IC, and shouldn't have to do too much other than outputting the right codes (although may need to do some debouncing, as well as shift-key handling)
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Old 26th Mar 2021, 10:34 pm   #109
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Default Re: The Transam Triton Personal Computer

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MM5745 National 78 4 10 Parallel Custom
MM5746 Semiconductor 78 4 9 Parallell Custom
Been out of action a few day this week having had the Jab !

Hand a look at these controllers they are close, having done a bit more work on the keyboard the controller seams to work it terms of putting out the correct codes, apart from the fact some of the data lines go to -12v for 0 and other go to Zero for 0, all go to +5v for 1.

Not all the key switches are working some only give one output and others neither. looking on the web, there are no spares out there for the key switches that I can find. Having taken a key out and remove the sensor element the chip has just come away from the small circuit board picture on this site. Key switch and mine below

There other option might be just replace the Hall Effect module put there is no reference to its part number, unlike older SD hall effect switches.
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Old 26th Mar 2021, 11:05 pm   #110
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Default Re: The Transam Triton Personal Computer

Good to hear you've made it back - Luckily I only had a bit of a headache for about a day after mine (often similar with flu one), but it's a bit random how people I know have responded from nothing to a few days.


If the keyboard's data outputs go directly to the main custom IC, then it would seem that it's output circuitry has gone a bit faulty. Otherwise, there may be some external level-converters etc. that may be at fault, so would need to Rev.Eng that circuitry, to see what might be wrong.
But if the Main IC is responding to all key matrix line inputs, producing outputs, and just some switches not working, then it would seem the main IC is mostly working (presumably producing the right codes) and it should be possible to convert the -12V levels to 0V ones, while retaining the +5V high levels.

I presume that there was a small silicon chip / die etc. fitted on that ceramic substrate, and is completely missing - so couldn't be resoldered, if it was originally and not wire-bonded etc.
Might have to have a look inside a good one, to compare, with a close-up shot.
I wonder if Micro-switch bought these Hall-effect ceramic-substrate SIL-modules as an off the shelf product, or whether they are custom to them?

Last edited by ortek_service; 26th Mar 2021 at 11:12 pm.
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Old 26th Mar 2021, 11:23 pm   #111
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Default Re: The Transam Triton Personal Computer

Here is the Pic of a good one from this site Micro_Switch SD switch module .

Could not find the chip that came off but it is very small !
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Old 26th Mar 2021, 11:25 pm   #112
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Default Re: The Transam Triton Personal Computer

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Originally Posted by GeraldSommariva View Post
Quote:
Originally Posted by Timbucus View Post
Quote:
Originally Posted by SiriusHardware View Post
I'm wondering if Tim might be able to consider testing the VDU IC as he has a working system? Some component suppliers, including some quite well known ones, have a habit of advertising ICs they don't actually have and only try to find them when anyone takes an interest.
I suppose I could do that without too much risk as Gerald seems to find that they are all just low as long as it does not have a dead short Vcc 5v to Ground as obviously mine is a standard Triton PSU without any luxuries of protection against shorts...
I am going to order one from littlediode as I am sure its dead, but before I do I want to check which version they have. Tim you said its need to be the A version SFF96364A on their site they don't specify. I give them a call tomorrow, they are not too far from me so may be I could go and pick one up.
I have ordered the VDU chip now so waiting for it to turn up, if was cheeper to order via Ebay then from their own web site Littlediode
SFF96364


The binary counter chip IC63 SN74LS163 is definitely dead and the VDU port latch IC51 SN74LS374 is dead too. As I replace ICs I and using sockets for the new ones (good idea ?). I had forgot how difficult it is to get those 20 pin IC out with out messing up the PCB.
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Old 26th Mar 2021, 11:42 pm   #113
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Default Re: The Transam Triton Personal Computer

When you are reasonably sure an IC is dead we always recommend snipping all the pins off it high up next to the body of the IC, removing the body and then desoldering and removing each pin individually, as it is much easier to remove a one-pin device without causing damage than it is to remove a 20-pin device.

Of course this doesn't apply if you want to be able to swap between the new device and the older, possibly faulty device to observe the difference in their behaviour. If you do, then you have to get it out the hard way, intact.
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Old 27th Mar 2021, 12:00 am   #114
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Default Re: The Transam Triton Personal Computer

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When you are reasonably sure an IC is dead we always recommend snipping all the pins off it high up next to the body of the IC, removing the body and then desoldering and removing each pin individually, as it is much easier to remove a one-pin device without causing damage than it is to remove a 20-pin device.

Of course this doesn't apply if you want to be able to swap between the new device and the older, possibly faulty device to observe the difference in their behaviour. If you do, then you have to get it out the hard way, intact.
Yes the good old cut out, I did have one of those Weller desoldering stations with the foot switch to activate the vac pump.
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Old 27th Mar 2021, 2:30 pm   #115
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Default Re: The Transam Triton Personal Computer

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Here is the Pic of a good one from this site Micro_Switch SD switch module .

Could not find the chip that came off but it is very small !
Thanks, for this picture that I hadn't originally spotted amongst all the info on the linked webpage. It does look rather much that these originally had bare silicon-die IC's wire-bonded to the substrate then covered with the protected black 'glob-top' epoxy. So it is surprising that they fell off (and wouldn't really be practical to re-attach if you did still have the IC die), but maybe there's an ageing issue with their glob-top compound.

I do recall RS selling similar 3-pin single output substrates like this, that I had some of. and there are people selling small 4-pin PCB's like this with a leaded 3-terminal 'transistor package' on the end. So it may be possible to make a small replacement PCB, if a suitable SM / leaded dual o/p hall-effect device is found, if replacement keyswitches are no longer available.

Regarding the CRTC VDU IC purchasing, it's quite common when a seller has their own website shop as well as using an online auction one, that prices inc. delivery are a bit different. Sometime its cheaper direct, as they don't have someone else taking a cut, but I have also found it's cheaper via an online marketplace - may be because they offer free delivery or there's some more direct competition from other sellers (although not too much for these quite rare ones!).
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Old 28th Mar 2021, 9:20 am   #116
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Default Re: The Transam Triton Personal Computer

I noticed that there's also quite a few other 4pin (So Dual?) Hall-Effect devices pictured here: https://telcontar.net/KBK/tech/Hall_effect

And they mention that Tesla may have made similar copies of the Micro-Switch sensor modules.
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Old 28th Mar 2021, 12:10 pm   #117
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Default Re: The Transam Triton Personal Computer

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I noticed that there's also quite a few other 4pin (So Dual?) Hall-Effect devices pictured here: https://telcontar.net/KBK/tech/Hall_effect

And they mention that Tesla may have made similar copies of the Micro-Switch sensor modules.
Yes I found these there are some out there on ebay, but I don't think they gave out a pulse output.
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Old 28th Mar 2021, 10:43 pm   #118
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Default Re: The Transam Triton Personal Computer

I'd assumed they all just switch on or off, when magnet was close-enough.
And so would give an out as log as a key was held down.

But maybe there was some extra circuitry in these that did debouncing by providing a fixed length pulse, rather than the main keyboard IC having to do this.
Or maybe it was to overcome issues with multiple keys being held down and the 2 of N system - as I can see that if you hold 2 keys down in different row & columns at the same time and these are all pulled to ground, then it would appear to controller that 4 keys would be held down on these rows and columns. Whereas a scanned-matrix system wouldn't have this issue, by only making one row etc. active at a time.

So I guess it's a case of doing some test on a working existing keyswitch, to establish exactly what it does.
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Old 29th Mar 2021, 10:12 am   #119
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Default Re: The Transam Triton Personal Computer

Run some tests on my keyboard switches of which some are not working, most produce a pulse 20ish micro seconds low when you press the key, other stay low as long as you hold the key down.

The ones that produce a low level on holding the key down are CTL Shift and Shift Lock. so they work as per the included screen shoot.

Still can not find any information on the encoder chip on this keyboard.
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Old 29th Mar 2021, 11:44 am   #120
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Default Re: The Transam Triton Personal Computer

That's useful info and shows that two types are used, just to complicate matters.
And the narrow-pulse type are used to overcome the 2 of N matrix issue of multiple keys being activate at the same time during rollover from fast multi-finger typing.
I've also just realised that switch debouncing may not be required with hall-effect sensors, so that may simplify what their (custom?) keyboard encoder has to do - basically a triggered look-up table ROM, that also has shift & ctrl key inputs to alter output codes.
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