22nd Mar 2021, 9:32 pm | #101 | |||
Octode
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,364
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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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22nd Mar 2021, 9:36 pm | #102 | ||
Pentode
Join Date: Mar 2021
Location: Liphook, Hampshire, UK
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Re: The Transam Triton Personal Computer
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22nd Mar 2021, 10:12 pm | #103 | |||
Octode
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Location: Barry, Vale of Glamorgan, Wales, UK.
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Re: The Transam Triton Personal Computer
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22nd Mar 2021, 10:21 pm | #104 |
Octode
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 1,298
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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 |
22nd Mar 2021, 10:30 pm | #105 | |
Octode
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Location: Barry, Vale of Glamorgan, Wales, UK.
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Re: The Transam Triton Personal Computer
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23rd Mar 2021, 12:28 am | #106 |
Pentode
Join Date: Mar 2021
Location: Liphook, Hampshire, UK
Posts: 125
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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. |
23rd Mar 2021, 1:50 am | #107 |
Octode
Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
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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 Last edited by ortek_service; 23rd Mar 2021 at 1:56 am. |
23rd Mar 2021, 11:29 am | #108 | |
Octode
Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
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Re: The Transam Triton Personal Computer
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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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26th Mar 2021, 11:34 pm | #109 | |
Pentode
Join Date: Mar 2021
Location: Liphook, Hampshire, UK
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Re: The Transam Triton Personal Computer
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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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27th Mar 2021, 12:05 am | #110 |
Octode
Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
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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; 27th Mar 2021 at 12:12 am. |
27th Mar 2021, 12:23 am | #111 |
Pentode
Join Date: Mar 2021
Location: Liphook, Hampshire, UK
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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 ! |
27th Mar 2021, 12:25 am | #112 | |||
Pentode
Join Date: Mar 2021
Location: Liphook, Hampshire, UK
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Re: The Transam Triton Personal Computer
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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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27th Mar 2021, 12:42 am | #113 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,586
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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. |
27th Mar 2021, 1:00 am | #114 | |
Pentode
Join Date: Mar 2021
Location: Liphook, Hampshire, UK
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Re: The Transam Triton Personal Computer
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27th Mar 2021, 3:30 pm | #115 | |
Octode
Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
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Re: The Transam Triton Personal Computer
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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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28th Mar 2021, 10:20 am | #116 |
Octode
Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
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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. |
28th Mar 2021, 1:10 pm | #117 | |
Pentode
Join Date: Mar 2021
Location: Liphook, Hampshire, UK
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Re: The Transam Triton Personal Computer
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28th Mar 2021, 11:43 pm | #118 |
Octode
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Location: Northampton, Northamptonshire, UK.
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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. |
29th Mar 2021, 11:12 am | #119 |
Pentode
Join Date: Mar 2021
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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. |
29th Mar 2021, 12:44 pm | #120 |
Octode
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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. . |