Jimhearne

Thank you very much for scanning those. It looks perfectly recreatable , no PAL's or GAL's that i spotted. I don't suppose there was a component layout as well, maybe possible to keep the component placement the same even if the tracking isn't. TI usually include the component layout with the schematics. I ordered a couple of TMS5220 chips, i believe these are compatible with the TMS5200 The TMS5200 seem to be in big demand for pinball and arcade machines so a bit pricy.

It's getting there, doing code for that board. The 990 needs a fair bit of code to initalise the VDT911 card and display any characters received on the screen. But, at the moment I need to type any code for the 990 into the programmers panel a bit at a time which is somewhat tedious. So, I'm looking at connecting another PIC processor to the buttons and LED's on the 990 programmers panel so i can download code from a PC via the PIC and effectively type it into the 990. It will be slow but at least it will be saved on the PC and i won't have to enter code a bit at a time !

Next stage of the TI 990 VDT911 interface card project. A VDT911 interface board for an original 911 keyboard or a PS/2 keyboard plus breakout for the video signal from the VDT911 card to send to a RGBtoHDMI and also 5V power on a USB port to power the RGBtoHDMI Jim

I've several VDT911 cards for my TI990 system but no monitors. I've one 911 keyboard but that's got a parallel output and there is normally circuitry in the monitor to convert that to balances line serial (like RS485) to send to the VDT card. The VDT911 card outputs a composite video signal and i've hooked it up to a RGBtoHDMI interface with the 6-12_BIT_YUV_Analog board. This is the output after fiddling around with the settings. The VDT911 outputs either 12 rows off 80 characters or 24 rows of 80 character, this is 24 rows at 50 hz Next stage is to make a Parallel to serial adaptor for the 911 keyboard and also a PS/2 to serial adaptor (or maybe both in one). Jim

The link https://dragonsweb.org/nextcloud. has an extra . on the end, i assume it should be https://dragonsweb.org/nextcloud I use Nextcloud for work, i hope it plays nicely with that. Jim

Where would i find Colin's Blog, sounds interesting. I must visit the Computer History museum this year, after checking if their 990 is on display and not just stuck in the stores which i suspect it is. But, i want to get my 990 doing something before i visit so i've a rough idea of what i'm doing just incase they ask me if i know about them. Jim

I don't supposed he has any TI-990 boards ? Any chance of scanning the TM990 manuals ?, I'm resisting collecting any TM990 boards as well as E-Bus and TI-990 but the TM990 manuals would be interesting if they contain schematics. Jim

I follow him, he has mentioned in the past that he wanted a TI-990 system

Looks like a hard drive. http://www.bitsavers.org/pdf/ti/990/disk/2272081-9701_CD1400_Feb81.pdf

This is the disk controller TFDC floppy controller from the TI990 series Schematics are available.

No problem, glad i could help.

If i was doing it i would use a PIC micro to scan the keyboard matrix and convert it to a USB keyboard protocol. But, i'm used to PIC micros, though i've only done one project with USB and that just emulated 2 keys for starting and stopping a CNC program from 2 big buttons. I just hacked up a example USB program from CCS whose C compiler i use on the PIC's You could do the same thing with an Arduino or one of the Raspberry PI varients as long as it has a USB interface and enough I/O pins to scan the matrix. A search for "keyboard matrix to usb" on Google revealed quite a few existing projects. Some are hard coded for specific keyboards, you would need one that was wither configurable or had the source code available so you could change the software yourself. I found a chip specifically for this purpose that looks interesting. https://www.sprintek.com/en/products/keyboard_ic/SK5120.aspx They seem to do boards as well, depends on what your budget is.

What is the connection from the keyboard to the old motherboard ? How many wires ? Are there any chips (probably 40 pin) on the keyboard pcb ? As jbdigriz says, it's probably ends up as a XT keyboard interface at some point and you can get XT to AT/PS2 keyboard adaptors ready made. But, it depends if the chip that converts the key matrix into XT codes is on the keyboard pcb or it was on the original 1400FD motherboard

An update for anybody following. After playing mix and match with the switch bodies (with seemingly different strength of magnets) and the new switch PCB's (with different sensitivity of sensors) i have manage to get the keyboard almost assembled again, just 10 switches short so i've left off the numeric keyboard switches until i get some more hall sensors. The switches all work in the FMT (Field maintenance test) keyboard test, once i can get it booting something i can type at normal speed i will find out if the switches are too slow for normal typing. The 715 terminal has now got a set of DS990/1 pcb's fitted and thanks to help from jbdigriz and especially piero it now boots from a Gotek emulating the TI FD800 8" drives. The screen looks like it has one of those anti reflective filters fitted on it (the ones that are like a stocking mesh ) and it's very dusty so that is blurring the picture. I will try cleaning it or maybe will have to remove it like most people seem to.

Thank you very much. Looks perfectly readable to me Jim

With large diameter solder it's hard to put the small amount you require into the joint. Also the tip size, lots of people on YouTube having trouble with soldering SMT and they are using huge tips, unless you are drag soldering you don't want a big tip (IMO)

I use 0.5mm solder for pretty much everything. I do have 0.3mm but as it's so small there is so little flux in it i find it's only usable with added flux and I only usually it on the really fine pitch SMT I use unleaded solder nowadays and actually prefer it to the old leaded but it has to be the stuff with 3% silver in it, the cheaper unleaded without silver is horrible to use. This is the stuff i used, it's silly expensive but a reel that size would last a hobbyist a lifetime. https://uk.farnell.com/multicore-loctite/631719/solder-wire-96-5-3-0-5-217-deg/dp/1257142?st=97sc Luckily work pay for mine. Despite soldering since I knew which end of the iron was hot, I've never mastered drag soldering. 😞

Good news. If you can I would really recommend assembling a new board in steps. Just assemble the bare minimum of parts until you can test that section. Them fit a few more parts and test that section. Much easier than trying to debug a complete board at once. I know it's much harder doing that with SMT parts than through hole. Probably easier for me as i still fit SMT parts with normal soldering iron (0.5mm tip) a pin at a time.

Well, that's a bit annoying. I couldn't remember what pin it was failing so i just tried it again. Everything i tried is now passing 😞 I suppose at least it gives me a spare programmer / tester.

Ok, my first full book scan with my new book scanner. Took about an hour to do 286 pages TM990 Microcomputer Catalog Microprocessor series May 81 What do you think ? Jim TM990 Microcomputer Catalog Microprocessor series May 81.pdf

Sending the interrupt over the E-bus was the last thing i was working on on these boards a few years ago before a house move and then since i've been distracted playing with the 990 stuff. As far as i can remember i had an i/o card sending the E-Bus INTEN signal, that being acknowledged , the interrupt code being sent across the E-bus and being latched into the CPLD, the processor was able to read the interrupt code but then i was having issues at that point. Can't remember for sure, unfortunately if i don't work on something for a while i forget a lot of stuff and i'm not very good at keeping notes so i have to sit down and go through it again.

My TL866-II died a few months ago as well, or rather it partly died , it started failing some logic chips (74244, 245 etc) on a specific pin but it will still read and program EPROMs I spent a few hours trying to fix it but couldn't find any difference in signals between the pins that were passing and the one that failed so maybe internal to the processor. So i bought a T56

Sorry, don't want to hijack your thread. Some quick pictures of my video card and a multi i/o Card, Floppy, IDE, serial , parallel, RTC card, and the proper backplane. Again one CPLD on each card is doing all the address decoding, E-Bus control etc. The I/O board has a space for a PIC which won't be on the next version, i was going to use it for PS2 keyboard and mouse but then realised i can implement the PS2 interface in the CPLD and i've moved the keyboard/mouse to the video card. Any caps and resistors needed are SMT on the rear of the boards which is why the boards look quite clean but i think still look retro. You can do the same back to back veroboard trick to make quick extender cards for DIN connectors.

Thank you, i thought you had seen my board before. I must get back to it, I've been distracted from it by all the TM990 stuff I've been playing with. The CPLD is doing all the stuff that would have been done with descreate logic controlling address decoding and the E-bus control. I'm not trying to do multi processor so it doesn't support that but it does do everything else on the E-Bus The CPLD start off as a Altera EPM7128 in a PLCC package but as i added extra features i maxed that out and then maxed out the biggest CPLD in that series. So i had to switch to a EPM7512 which is a 3.3V device but with 5V compatible I/O, the adaptor board has a 3.3V reg on the back. Unfortunately trying to emulate the 612 memory mapper in the CPLD takes up a lot of cells (CPLD Are not good for latches / memory as i've found) and i've maxed out so i will have to have a cut down version. The prototype backplane is 2 layers of veroboard stuck back to back, one set of pins is soldered on the top, the other set pass through the top layer and where they pins pass through the copper is chamfered with a drill bit to make clearance for the pins but not enough to cut the tracks.

Thank you, i thought you had seen my board before.