Texas Instruments 928 Terminal with 931 Support ROM

[jbdigriz]

20 hours ago, brantcy said:

Thanks you two!

 

    I actually work with/around/for a guy here in NM that has a 7k sq ft facility (and quite a few storage locations as well I gather) that are absolutely jammed to the ceilings with, all sorts of vintage tech, hundreds of terminals, systems, you name it.  He started collecting in the 80's and he asked me to help him parse and sell stuff for him.  I have learned a ton, and it's been awesome.  Initially yes, I met him while looking to get an older keyboard.  The modern one I had discontinued a replacement wrist rest after a single year.  They wanted me to buy their new and "improved" shiny rgb keyboard for $250.  Sometimes I can be a bit, rash, I guess, but i took offense and decided to build my own, and after some self educating, learned about the keyboards of my youth being far and away better than anything modern, and well, here I am.  I currently have 60ish? keyboards, including actually @FarmerPotato, a TI 924 VDT keyboard, although it's missing the "1" key from the numpad.  I'm not really aiming to come here and start "hawking(is that even the right word?) my wares", but I really haven't got a good use for it, not as good as you have anyway.

 

This sounds like the place I've been meaning to visit before it gets picked over. I have to admit I'd be looking for deals on stuff I can't afford to buy on Ebay, and they do put some items there. It would be disappointing though to make an expensive trip and find a bunch of terms and computers missing their bespoke, non-PC keyboards.

 

20 hours ago, brantcy said:

    Heck, I'd probably have dragged a few terminals home by now as well, but digging them out is gonna be a, task, to put it mildly.  Also, @jbdigriz the S300 does use the same keyboard as the 931, I forget where I found those manuals, but bitsavers is as likely as anywhere - although I did a 5-day hyper-focusing event (it's, something that i struggle with, but it comes in useful sometimes...) , and i've scoured the net, obscure websites, and lots more.  I've turned up lots of good information, but not yet what I was searching for.

Yes, you should drag home a 931 or a 924 and get it going. I plan to make some 990 and/or Business System DX10 and DNOS simulations availble online soon, using Dave Pitts' simulator. There is also an effort to put a real 990/12 online. Maybe a /10A also. And an S1500.

 

20 hours ago, brantcy said:

    I actually ran into that SMU collection online, and it's awesome that you're able to access it!  I'd very much appreciate if you were to find anything useful!  We have a bit of a "library" of manuals and docs, but idk what's needed or isn't.  I can upload some pictures of the binders and manual spines, and you can perhaps tell me if anything might fill a gap in knowledge?  Aside from that, he's also got just boxes and boxes of manuals, but as with the terminals, it's kind of a scavenger hunt to find things in there.

That would be most welcome. I'm scanning in some manuals now that are not online at present. Also compiling lists of manuals for updating the manx-docs.org database and setting up a parts database.

 

Your source stock many NOS OE repair parts? Power switches, that sort of thing?

 

20 hours ago, brantcy said:

 

    I'm 42, 7 credits away from an IT degree, and honestly, I don't even care anymore.  I want to follow this path.  I'm also a very disabled war vet, so I have some latitude to follow my own, path I guess.  I'm not about to gut any of these board to make some of the ridiculous things I've seen.  I want to use this keyboard, because it's a damned fine piece of work, and it deserves to be used.  If I can do so without damaging or destroying anything in it, then I will.  If not, I won't.  Last thing I'll say on it is that I have found my passion with vintage computing.

 

    Here's a picture or two of that keyboard I mentioned, for the 924, or 8?  I forget as much as I discover, infuriating!
 

Yes, that's a 924 keyboard. 931 kbd is 2228995-0001 (US layout) The 928 kbd is HP PN C3344-20601. There is a TI PN I'm sure, but I haven't found it yet.

 

Thank you for your service.

Edited September 1, 2023 by jbdigriz

[jbdigriz]

@brantcy, if you can find a copy of any 940 manuals, period, and/or BS300 (or BS200) maintenance manuals that would indeed be helpful to several people here and elsewhere. The BS200 and BS300 each consist of an SBC installed in a modified 940 terminal, which serves as the system console. 931s were used as the user terminals. Here is link to a 940 description on bitsavers, https://bitsavers.org/pdf/datapro/alphanumeric_terminals/Datapro_C25_TI.pdf I cannot rule out that a 931 keyboard could be used as the console keyboard, and I have also heard something along those lines, but it is different from that pictured, at least. We can say for sure that 931 keyboards were used with the BS300, attached to 931 terminals, at any rate.

 

931 keyboard pics for reference: https://imgur.com/gallery/uzQ4Lee 2228995-0007 SWE/FIN layout.

 

I also note that the 924 can emulate the 931, VT220, and VT100. Keys and layouts different, however.

Edited September 1, 2023 by jbdigriz

[+FarmerPotato]

I have got the 928 disassembled, and removed the broken power switch. 

 

This is a DPDT switch made by Preh, type ME5A. (Not "Mesa"). The 928 has the PCB mount, pin style.  A panel mount or solder lug style is in the Commodore 1082 and other monitors.

 

This blog,  Fixing the HP 700/43 Terminal repairs the same ME5A switch.
 

 I'm searching for a replacement. 

 

Also, I can't figure how the two copper leafs fit back in... I'm sure they bridge the contacts, but how?

 

 

 

Preh is long gone from switch making.  
 

 C&K switches of this type have a dufferent,  rectangular grid. 

 

I'm going to have to match this, unless there is a way to make the ME5A work.

 

Here's a starting search on Digikey

Mouser search turned up C&K NE18 switches. 

 

 

Edited September 3, 2023 by FarmerPotato
Relevance

[Stuart]

@FarmerPotato Did you see the page [http://chain.3dgrafika.cz/preh/]? Right down the bottom of that page, the PREH ME5A 70060-017 might be a replacement if you swap over the metal bracket? And that switch appears to be available from Radwell.

 

Or if you used a panel mount / solder lug version, if you mounted it upside down, is there room to run wires from the lugs down to the PCB?

[+FarmerPotato]

I misread:  NE18 from C&K are 250 VAC rated and might work. 
 

NE182AEEP6AMP

 

Is the part with:
2A : DPST

EE : push-push on-off

P : pins for PCB (lower current! Adequate for 928.)

 

The pin spacing is 12 mm and I understand the ME5A has 15 mm. The footprint is different at least that way, but I'll try to adapt it.
 

 

 

[+FarmerPotato]

On 9/1/2023 at 3:25 PM, Stuart said:

@FarmerPotato Did you see the page [http://chain.3dgrafika.cz/preh]? Right down the bottom of that page, the PREH ME5A 70060-017 might be a replacement

Thanks, Stuart, but I can't find any ME5A that ship to US. I don't think Radwell really has all the stuff they  show. 
 

I'm going to order an NE18 by C&K for $10. Seems like the closest. 

 

Mounting ring removed.  (Amanda found a way.)

 

The tiny rectangle is where a tiny pin broke off. The piece  slides left and right.   On the white plunger, you can see the intricate path which the pin follows. First push, the pin goes up the right side and then rests. (It moves left/right.) You can see the second push forces it out to the left. Ingenious!
 

Need my PCB drill bits to try Gltcher's repair. But I cannot figure how the copper leaf blades fit back in!

 

 

Edited September 3, 2023 by FarmerPotato

[brantcy]

On 8/31/2023 at 7:03 PM, jbdigriz said:

This sounds like the place I've been meaning to visit before it gets picked over. I have to admit I'd be looking for deals on stuff I can't afford to buy on Ebay, and they do put some items there. It would be disappointing though to make an expensive trip and find a bunch of terms and computers missing their bespoke, non-PC keyboards.

 

    @jbdigriz, the place I'm referring to is in Southern NM, Las Cruces - Edgar Digital Electronics.  As to what you'd find, I think you'll find a lot of both.  Plenty of incomplete pieces in every direction, plenty of complete items as well.  If you truly have an interest in vintage computing - electronics period, you'll not be disappointed.  Plenty of folks have picked at things, but there's just entirely too much stuff, and it also never hurts to ask for what you're after, he has a handful of off-site locations that are certainly less seen.  As far as deals, he does consider ebay sold prices, but also considers whether the item in questions is 100% or not (usually untested is a lot cheaper)  also, he keeps in mind that a local sale is easier for him, eBay doesn't take 25-30% etc.  It's definitely not a firesale, but it's reasonable and he bargains with folks.  You'd certainly not consider it a waste of your time & money.

 

On 8/31/2023 at 7:03 PM, jbdigriz said:

Yes, you should drag home a 931 or a 924 and get it going. I plan to make some 990 and/or Business System DX10 and DNOS simulations availble online soon, using Dave Pitts' simulator. There is also an effort to put a real 990/12 online. Maybe a /10A also. And an S1500.

 

That would be most welcome. I'm scanning in some manuals now that are not online at present. Also compiling lists of manuals for updating the manx-docs.org database and setting up a parts database.

 

Your source stock many NOS OE repair parts? Power switches, that sort of thing?

I had a look around on Wednesday for a TI terminal, but I didn't have much spare time, or any luck.  So darn many Vax/Sun/Dec/HP/etc./etc. things, and it's all packed so dense.  I'll upload some preliminary pics if my phone hasn't deleted them already, and for repair parts, he has gobs and gobs of things from resistors to every size vacuum tube you might imagine, and loads in between.

 

 

On 8/31/2023 at 7:03 PM, jbdigriz said:

Yes, that's a 924 keyboard. 931 kbd is 2228995-0001 (US layout) The 928 kbd is HP PN C3344-20601. There is a TI PN I'm sure, but I haven't found it yet.

 

Thank you for your service.

The KBD pictures I uploaded are for p/n - 2229155-0001, and this one is Revision E.  Also, the 924 vdt manual ought to have a parts list in the early sections.  I know the 931 manual has got a list.

 

And you're welcome!  I'm excited to find other people that share this vintage hobby!

 

(I hadn't expected such quick responses, so sorry for the delayed reply.)
 

 

 

Edited September 3, 2023 by brantcy

[brantcy]

On 8/31/2023 at 7:47 PM, jbdigriz said:

@brantcy, if you can find a copy of any 940 manuals, period, and/or BS300 (or BS200) maintenance manuals that would indeed be helpful to several people here and elsewhere. The BS200 and BS300 each consist of an SBC installed in a modified 940 terminal, which serves as the system console. 931s were used as the user terminals. Here is link to a 940 description on bitsavers, https://bitsavers.org/pdf/datapro/alphanumeric_terminals/Datapro_C25_TI.pdf I cannot rule out that a 931 keyboard could be used as the console keyboard, and I have also heard something along those lines, but it is different from that pictured, at least. We can say for sure that 931 keyboards were used with the BS300, attached to 931 terminals, at any rate.

 

931 keyboard pics for reference: https://imgur.com/gallery/uzQ4Lee 2228995-0007 SWE/FIN layout.

 

I also note that the 924 can emulate the 931, VT220, and VT100. Keys and layouts different, however.

@jbdigriz I'll keep my eyes open for TI manuals.  I've seen a few, but they were for the Silent 700 & TI Pro PC.  There'll be more - somewhere.

[+FarmerPotato]

@brantcy OMG! Edgar Electronics!

 

He was at VCFSW in Dallas in June. His booth was incredible. I saw twin 8" floppy drives in the Altair blue case. I hoped to get some help with my 8" drive. I was able to buy a whole box of 8" floppies-- even floppydisk.com has fewer  left to sell. 
 

I asked about a serial  card for Altair. Got a  guided tour browsing through a box of S100. Ended up purchasing a floppy controller and a serial I/O card for like $80. Amazing. 
 

I didn't know yet what kind of keyboard I needed for the 928, or I'd have asked. 

 

Your description makes me smile. I would love to go there. 
 

 

[jbdigriz]

4 hours ago, brantcy said:

 

    @jbdigriz, the place I'm referring to is in Southern NM, Las Cruces - Edgar Digital Electronics.  As to what you'd find, I think you'll find a lot of both.  Plenty of incomplete pieces in every direction, plenty of complete items as well.  If you truly have an interest in vintage computing - electronics period, you'll not be disappointed.  Plenty of folks have picked at things, but there's just entirely too much stuff, and it also never hurts to ask for what you're after, he has a handful of off-site locations that are certainly less seen.  As far as deals, he does consider ebay sold prices, but also considers whether the item in questions is 100% or not (usually untested is a lot cheaper)  also, he keeps in mind that a local sale is easier for him, eBay doesn't take 25-30% etc.  It's definitely not a firesale, but it's reasonable and he bargains with folks.  You'd certainly not consider it a waste of your time & money.

Thought so. Yeah, I look forward to a trip there, sometime reasonably soon. Good luck finding a term, and thanks for posting.

[jbdigriz]

5 hours ago, FarmerPotato said:

Thanks, Stuart, but I can't find any ME5A that ship to US. I don't think Radwell really has all the stuff they  show. 
 

I'm going to order an NE18 by C&K for $10. Seems like the closest. 

 

Mounting ring off (Amanda found a way.)

 

The tiny rectangle is where a tiny pin broke off. The piece  slides left and right.   On the white plunger, you can see the intricate path which the pin follows as you push-on push-off. 
 

Need my PCB drill bits to try Gltcher's repair. But I cannot figure how the copper leaf blades fit back in!

 

 

That looks...iffy. I have repaired a switch or two in nearly as bad a shape, but it was a temporary fix. If the NE18 doesn't work out, I'd go with Stuart's suggestion and get an alternate action panel mount pushbutton and cut/grind/punch a bracket insert  to fit  the replacement switch barrel. It won't be original but it'll work fine.

[+FarmerPotato]

The NE182UEE6AMP was not a great fit.  For one, the switch body is shorter.  3 pins could be forced into the existing ME5A footprint, with the fourth pin necessarily jumpered. But then the actuator would be too short, and the mechanical support ring would not fit at all. 

 

We chose to put the NE18 switch on the existing retaining ring. That makes only a slight difference in actuator length.  All 4 pins would be wired to the PCB contacts.  But then Amanda asked why not turn the switch upside down? That is a much neater solution.  18AWG wire, crimped on the PCB end, plus shrink tubing.  There is still exposed copper on top. 

 

While in there, we desoldered and socketed the ROM.  Same for the HCS upgrade ROM.  Both are now dumped. 

 

Jobs to do next:

1. Replace the foam bumper protecting the cathode. Before the foam rotted, it was held on with double-sided tape. 

2. Replace two RIFA caps.

3. Replace the 2032 battery.  It's the standard 3-pin type, with permanent contacts.  But the PCB has another via, so it can accept either 2 pin or 3 pin.  20 mm distance between pins. 

 

 

[jbdigriz]

22 hours ago, FarmerPotato said:

But then Amanda asked why not turn the switch upside down?

Good call, Amanda.

Making progress, excellent!

Edited September 11, 2023 by jbdigriz

[+FarmerPotato]

FYI: the ROMs have been dumped successfully. 
 

I replaced the safety capacitors and the coin battery. The power switch toggles. The EPROM in its new machine pin socket kept popping out. So I flattened the legs. (They were in a bow shape, maybe an advantage in PCB thru holes.) 

 

Glued on a new foam protector for the electron gun. Reassembled the whole thing  today. 
 

Alas. It powers on silently with just one bright horizontal green line. 
 

I have to learn some more about CRTs. Ideas seem to be DC power to the deflection coil. Or a service switch activated. A vertical gain IC. Or any type of loose connection. 
 

RetroTech video & comments
 

 

[atrax27407]

Did anyone ever get the ROM from the "928 to 931 Conversion Kit" dumped?

[+FarmerPotato]

1 hour ago, atrax27407 said:

Did anyone ever get the ROM from the "928 to 931 Conversion Kit" dumped?

Yes, I have it. Was waiting for Jim to check if HCS minds. 

[atrax27407]

OK - wouldn't mind a copy if they give the OK.

[+FarmerPotato]

Do you have a 928 to upgrade? Or just interested in the code (x86)?

 

The internal ROM is 32K, about 24K used, in a OTP DIP32. The plug in module has a DIP28 8K, but in a DIP32 footprint. A PLD--I guess  GAL22V10, to map address lines.   I haven't  desoldered it. Guess: the PLD overrides just the top 8K, but the slot might accept a full 32K. 

 

The slot is too small for socketed chips. I realized  after I put a socket under the EPROM!

 

 

[jbdigriz]

13 hours ago, FarmerPotato said:

Yes, I have it. Was waiting for Jim to check if HCS minds. 

It's on the stack, right along with determining if it's okay to post the Microgate 931 emulator for MS-DOS. I think that company is still around, and in Austin, in fact. Are you familiar with them by any chance?

 

HCS appears to have shut down long ago, and the owner I think possibly deceased for some time. It looks like there may be a relative I may be able to reach out to, though. We'll see. Also, there are some competitors who also sold 3rd party upgrades for TI equipment who may have leads. Of course, if anyone from Houston or TI here in the forum remembers or had dealings with HCS (Houston Computer Services), any info or contacts would definitely be helpful and appreciated.

 

Thanks,

jbdigriz

 

Edited September 18, 2023 by jbdigriz