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iprefermuffins
August 21st, 2010, 07:27 PM
I recently got my hands on a VT102, but it doesn't seem to be quite working. All the characters seem to be corrupted:
43354336

Having had no prior experience with this kind of hardware, I'm wondering if anyone has seen this before and could tell me if it's something I could fix myself. Something wrong with the character generator ROM, maybe?

I also received a VT240 (powers up but displays some kind of error about the main board), a VR201 monitor, and an LA50-RA printer, none of which I'm as interested in. So they're available for anyone interested who can pick up from central Massachusetts.

NeXT
August 21st, 2010, 10:11 PM
Are you sure that you have all your communication settings correct?
Also, was the VR201 monitor compatible with the VAXstation 2000 or was it limited ot the DECmate/Rainbow systems? (which I assume use their own proprietary monochrome video signal)

iprefermuffins
August 22nd, 2010, 07:10 AM
The VT102 isn't connected to anything yet. Those two pictures are of the setup screens, and if I put it into offline mode and start typing, the characters are all messed up in the same way. So I don't think it's a communication settings issue unless it somehow has to be connected to display characters properly...

I have no idea about the compatibility of the VR201. Is there some identifying feature or label I should look for? If it helps, I think it's a VR201-A (it's white).

MikeS
August 22nd, 2010, 08:20 AM
I recently got my hands on a VT102, but it doesn't seem to be quite working. All the characters seem to be corrupted:
43354336

Having had no prior experience with this kind of hardware, I'm wondering if anyone has seen this before and could tell me if it's something I could fix myself. Something wrong with the character generator ROM, maybe?Possible, but without consulting the schematic it could probably also be the video RAM or buffers; interesting that spaces in text show as $$s (bit3 high?) but the rest of the screen is blank.

First thing to try: move any socketed chips back and forth a bit in their sockets if possible, or remove and (carefully) replace; assuming multiple socketed video RAM chips, try exchanging them to see if symptoms change.

Lou - N2MIY
August 22nd, 2010, 06:50 PM
Yes, the third bit from the least significant end is stuck. It could be the chargen rom or some other latch/buffer. I have not seen a VT102 FMPS (print set) on bitsavers or elsewhere. The VT102 is a cost-reduced VT100, but probably close enough to figure this out with only VT100 prints and the VT102 board. I have repaired a VT100 with a silimar problem once, but it took a few hours to get through.

ISTR that the VT102 had very few (if any) sockets. I have one, but it's deep in the back of a closet.

VR201 works with many machines. VT240, decmate II, decmate III, Pro series, Rainbow. The LA50 will make a nice local printer for either the VT102 or VT240.

Lou

Lorne
August 23rd, 2010, 07:28 AM
I believe the VT100 was a rebadged Televideo 925.

If so, I gave Bitsavers a Televideo 950 Maintenance Manual (59MB file) a while back, and it has troubleshooting info for the 910, 825 & 950 in it.
It might be worth pulling that down from Bitsavers.

I have a couple TV910 boards, and a TV950 board (some working parts and some not working), so if you need a part, I might have it.

Also see this post titled Wrapped Video - at the end is some info on who might have parts/knowledge for repairs.


http://www.vintage-computer.com/vcforum/showthread.php?17780-Wrapped-video&highlight=Wrapped+video


EDIT: Whoops - forget the comment above about a VT100 being a rebadged Televideo - I was thinking of a Stratus V101 which is a rebadged Televideo.
In any case, the guy with the parts/repair knowledge (in the link to the other thread) also has DEC stuff.

Lou - N2MIY
August 23rd, 2010, 02:50 PM
The VT100 technical manual is on bitsavers and is extremely detailed and well written. I am sure that most of the theory also applies to the VT102. I wish, however, that at least the print set for the VT102 would turn up.

Lou

iprefermuffins
August 27th, 2010, 06:55 AM
Thanks for the input, everyone. I studied the VT102 board and the VT100 FMPS, and the affected area (char gen rom and the latches and buffers) seems to be the same or very similar. I'm at a loss for how to actually identify what's going wrong though. I have a feeling that a logic analyzer or oscilloscope would be useful here, but I don't have access to one at the moment, unfortunately.

Lou, you mentioned you had repaired a VT100 with a similar problem before. Can you describe what you did to diagnose and fix it?

Here's an interesting symptom: When I try to switch to the alternate chargen set (which there isn't a rom for), typed characters mostly show up as white rectangles as expected. However, the first few characters on each line appear to be cycling rapidly over a sequence of assorted symbols. I wonder if this indicates a problem with latch timing or something similar.

saundby
August 27th, 2010, 09:36 PM
If the VT-102 ROMs are socketed I could potentially post the contents of mine. I won't have time to pop it open this weekend, besides, my workbench is already full. But I'll put this on the task list board and try to get to it soon.

If you've already reseated any socketed ICs, look at the pins on the board for a bad joint. Also make sure boards are seated well and the connectors look good.

Yes, an o-scope helps a lot with problems of this sort. A logic probe could see if a line is getting toggled, too.

Lou - N2MIY
August 28th, 2010, 05:52 AM
I pulled out my notebooks and can tell you about my VT100 repair. There was a stuck bit on the output of the DC011 video timing IC. Specifically LBA6.

You will see that on page 4-62 and 4-63 0f the VT100 rech manual (my hardcopy one here is ek-vt100-tm-003) there are timing diagrams for the line buffer outputs. I watched them with a scope, looking for transitions, not correctly timed transitions, but any transitions, and LBA6 was stuck. With my logic analyzer, I could have looked for properly timed transitions, but it didn't come to that.

From the timing diagrams, I was able to fabricate the LBA6 timing from LBA4 and LBA5 with a 7402 and a 7473A. The DC011 chip is unobtanium and the fun of this hobby for me is fixing everything (sound like Tony Duell?) See this photo of the "repair": http://www.vintage-computer.com/vcforum/album.php?albumid=56&attachmentid=2421

Your problem is slightly different. My problem produced screens of garbage, where yours the problem is further "downstream". If you have the VT100 print set, your problem is on sheet 5 (BV5). You need to look at the data lines on the line buffer ram outputs, tri state buffer, char gen latch, and if they're all good, I might suspect a bad input on the chargen itself. Remember, not only must the signal coming to an input be good, the input itself must be functioning. If I did not have my scope, I would build a crude logic probe with an LED and maybe a 74LS00 as an input buffer. If the LED flickers, you've got transitions. If not, it's stuck.

Kind of off topic, but if anyone is intersted in examining the "raw" contents of the VT100
chargen rom, I desoldered one, dumped it, and manipulated it in excel to draw the characters by turning cells red or white. Send a PM with a proper e-mail address and I'll send the spreadsheet.

Lou

MikeS
August 28th, 2010, 06:05 AM
I could be wrong of course (often am) but if it were the CG wouldn't the rest of the screen also be $$s and not just the spaces in the text? Kind of looks like the video memory isn't being loaded properly in the first place...

Lou - N2MIY
August 28th, 2010, 06:21 AM
Mike,

If one input on the chargen rom was broken and stuck, then the current problem would be exhibited. Usually I too find that outputs are broken, not inputs, but I thought it was worth leaving all possibilities out on the table.

For anyone interested,

The way this character generator works is that there are 11 address lines. Four (A0 to A3) select one of the 16 dot rows (although only 10 are displayed) and the other 7 (A4 to A10) select the character of interest (by ascii code). The output of the rom is the dot row data, that goes into a serial shift register (because the CRT draws the lines one row at a time).

Lou

MikeS
August 28th, 2010, 06:45 AM
Mike,

If one input on the chargen rom was broken and stuck, then the current problem would be exhibited. Usually I too find that outputs are broken, not inputs, but I thought it was worth leaving all possibilities out on the table.

LouNo, I wouldn't exclude the CG ROM either (it is the first thing that comes to mind with symptoms like this), but I was just thinking that if the CG incorrectly translates the space character then they would all be wrong wherever they are. But when I have another look I see that the incorrect ones are all also underlined and so are quite probably a different character.

Might be worth while to compare some other characters to what they should be; can't quite make out some of the odd characters, but it looks like it might not just be bit3.

Anyway, I'll leave it to you guys with VT100 experience and schematics ;-)

Lou - N2MIY
August 28th, 2010, 06:54 AM
Mike,

There is more than one ascii code in this rom that produces an empty space. They are 0, 32, and 127 (decimal). I agree that checking some other characters is worthwhile also. I tossed my scrap paper already, but I think I checked enough other characters to see the other bits all toggle. If I can't find those scraps, it should be rechecked.

Lou

MikeS
August 28th, 2010, 07:33 AM
Mike,

There is more than one ascii code in this rom that produces an empty space. They are 0, 32, and 127 (decimal). I agree that checking some other characters is worthwhile also. I tossed my scrap paper already, but I think I checked enough other characters to see the other bits all toggle. If I can't find those scraps, it should be rechecked.

LouWhen I read that only seven bits are used (and underline is thus presumably done separately) I was back to "so why aren't *all* spaces wrong," but looking at the character set you kindly sent me off-list (thanks again) I see that it could be a 'different' space after all.

Are those even all valid characters? If not, it'd sure point the finger of suspicion at the CG ROM...

Assuming that it's a socketed standard 27xx, it'd be simple enough to try replacing it.

I'm not 'into' VT100s, but curious: are there any alternate character set images out there for that empty socket?

Chuck(G)
August 28th, 2010, 08:09 AM
My eyes aren't what they used to be, but are those AVO characters displayed for the "P" (looks like a paragraph mark) and the "I" (hard to say what it is)? If so, I wonder if de-installing AVO might be a good initial test.

MikeS
August 28th, 2010, 09:05 AM
My eyes aren't what they used to be, but are those AVO characters displayed for the "P" (looks like a paragraph mark) and the "I" (hard to say what it is)? If so, I wonder if de-installing AVO might be a good initial test.Ah, that sounds like what they are; they don't look like any standard characters, but they don't look like random junk either (and the alternate CG is not installed)...

Leave it to Chuck, as usual...

Lou - N2MIY
August 28th, 2010, 12:12 PM
Ok, so this all was really killing me, so I got the VT102 out of the closet and took the cover off.

As I remembered, there is no separate AVO board in a VT102. The VT102 is a cost reduced VT100, BUT I seem to remember that the basic AVO functionality is built in. Unless extra roms are plugged into the VT100 AVO, it only provides extra character attribute ram (underline, bold, blink, reverse video...) I have also repaired a broken VT100 AVO, so I have been all through its logic once before.

As I again look at the OP's screen shots, they don't all look like valid characters. There's got to be something else wrong too.

In the VT102, only the processor roms are socketed. The character generator rom is soldered to the board. It is ALSO 23-018E2, this is the same chargen rom as a VT100. (I didn't know this before, but it's not surprising.)

This rom is not directly plug compatible with a 2716. Dec used the 8316E rom. The chip selects are not the same sense as 2716 (I'm not sure if they're always that way, or were mask programmed that way). I seem to have in my notes that pin 21 needs to be low (not the usual high on a 2716) for the chip to be selected. I had to do something funky like this to dump the rom in my eprom programmer (telling the programmer it was reading a 2716, folding pin 21 out and tieing it to ground.)

It's useful to note though that the VT100 alternate character gen rom socket can be jumpered to accept a real 2716 (jumpers W4 out, W5 in). I have not tried this.

I can take photos of the VT102 main board and upload to an album here if anyone is interested.

Lou

MikeS
August 28th, 2010, 01:56 PM
If I didn't already have too many terminals I'd pick up a VT102 just to really join in the conversation ;-)

Maybe the OP can type the whole character set (at least >31) in local mode and show us what it looks like on screen?

iprefermuffins
August 29th, 2010, 12:17 PM
Maybe the OP can type the whole character set (at least >31) in local mode and show us what it looks like on screen?

I'll see if I can do this and take a picture sometime soon. I did notice that, instead of the third-bit-high character replacing the correct one, it overlays it (so space is overlaid with $, ! is overlaid with %, etc.) Also, lowercase characters seem to be overlaid with their uppercase versions, so there may be something funky going on with the 6th bit too. I think this is what's happening for all cases where it's displaying a character that doesn't look valid - it's actually displaying 2 or more valid characters at once.

I saw in the user guide that the VT102 can take an alternate chargen rom, and if I cut a jumper it'll replace instead of supplement the original one. If it is a bad rom, would I be able to fix it this way?

iprefermuffins
September 2nd, 2010, 09:30 PM
I'm starting to suspect it's a bad ROM. I hooked up an LED as a "logic probe" as Lou suggested, to pin 2 (which I believe is the 3rd bit of the character address). When I type a screen full of dollar sign characters, the LED is fairly bright as expected since that bit should be high for '$'. When I type a screen full of space characters, the LED is considerably dimmer, as I would expect since that bit should be low for ' ', yet the characters still show up as '$'. Given that the input looks correct, and the same output is appearing for two different sets of input, I'm concluding the chargen rom is where things are going bad.

I don't own a rom programmer, so I'm wondering if anyone would be willing to program a suitable IC for me? I would be happy to pay the cost of the part and the postage/shipping.

Another thing I didn't mention before: the keyboard is missing 3 keys. Does anyone know where I might be able to obtain replacement ones?

Lou - N2MIY
September 3rd, 2010, 02:36 AM
I can program a 2716 for you. A good trick would be if we can disable the existing rom that's soldered to the board, put the replacement rom in the alternate chargen rom socket, and use that instead. It may save you the trouble of desoldering the old rom. I would need to mess with this over the weekend. I will report back. If this is successful, I can mail the rom to you.

As for the keys, I am in a similar position. I have one perfectly good VT100 keyboard that is missing three keys. I have no clue where to scavenge keys, but many dec terminals used this style of key. I've always figured that whatever was printed on whatever junk keys I got, I could paint overwhat was there, or stick a label on.

I will say this though - the reason VT100 keys seems to get lost, is that the plungers that the keys sit in get cracks on their outside corners. The keys get loose, and then fall out. I can take and post a photo of this problem if anyone is interested. Not only do the cracks make the keys loose, but the travel doesn't feel right when one pushes down. This seems to me to happen most often on the top row (number keys) and on the keypad. These keys must take an extra beating with more lateral force then the others. Fortunately, these plungers can be replaced! I was at a scrap yard and bought three raw, bare keyboards (sans keys, and not even soldered to a PCB) but with all the plungers. So I have a supply of plungers.

Lou

MikeS
September 3rd, 2010, 08:11 AM
I've got a few boxes full of miscellaneous old keyboards; any chance of a good closeup of the plunger and back of the key in case I've got something suitable? Sounds like the kind with square stems that fit into flimsy square 'boxes'?

Lou - N2MIY
September 3rd, 2010, 05:02 PM
Mike,

Yup, square stem and flimsy square boxes. The boxes crack at the corners. Here's the key: http://www.vintage-computer.com/vcforum/album.php?albumid=51&attachmentid=4405 and the "plunger" or "box": http://www.vintage-computer.com/vcforum/album.php?albumid=51&attachmentid=4404 .

Sorry the pictures are so blurry (consumer camera that can't do good macro shots). That's supposed to be a steel rule in the photos for scale with 1/32 graduations. Anyway, the outside of the plunger is 0.315" square and 3/4" long. The square part on the key that fits in the plunger is 0.275" square.

The tops of the keys on these keyboards have slightly different curvature depending on the row.

Lou

Lou - N2MIY
September 4th, 2010, 08:41 AM
Folks,

Well, here's how to replace the character generator rom in the VT102 with a 2716: http://www.vintage-computer.com/vcforum/album.php?albumid=58&attachmentid=4409

Cut the two shorting jumpers shown. The one on the upper right disables the existing rom. Cut the one on the lower left to allow use of the 2716. Fold out pin 21 on the 2716 and wire wrap it to pin 24. This ties the Vpp pin high. Fold out pin 18 and tie it to pin 12. This ties the chip select low (selected). Plug the 2716 into the alternate chargen socket.

This works and that's it. No soldering required. The VT100 will be similar. If anyone is ever interested, I can photograph that mod also.

Lou

iprefermuffins
September 7th, 2010, 09:41 AM
Lou, nice job getting that working. The modifications look pretty straightforward, so hopefully the ROM is the cause of my problems and this is all that I'll need to do to fix it. How do you disconnect the jumpers? Did you just cut one lead, or did you desolder it?

It would be great if you could mail me a programmed rom. Should I PM you with my address, and we can discuss the details?

And Mike, I would be very interested in getting some keys from you, if you have the right ones and are willing to part with them. It sounds like Lou would be too. I should check if the plungers on my missing keys are cracked, but I think they looked fine at a glance.

Kevin

MikeS
September 7th, 2010, 11:16 AM
Well, you (Lou) said that they're all the same; these plungers are from an LA36 but they don't quite look like yours as far as I can tell. There's a little extension on the side with a slot, and a wire "hook" rides in this slot to retain the plunger. Length=19mm.

Not much chance of the legend being anything you could use, but you did say you were prepared to paint; check the angle of the stem.

44204421

Lou - N2MIY
September 7th, 2010, 03:15 PM
Mike,

I looked at your picture of the plunger and thought "what the heck is that box on the side???" So, I went out to the garage and pulled a key on my LA36. I happened to pull one from the small keypad on the left. I pulled the one for 110 baud, and it had a little box on the side like yours! But, I spotted right away that the side box and wire hook are the mechanism that holds the key down (like caps lock). So, I pulled a key with a normal spring back action (I picked control), and it looks like a "normal" plunger like the one in my blurry photo.

So, for keys, it looks like you have a winner!!! Your plunger at 19mm long is 3/4" long like mine. How many of these keys do you have? The keyboard I have is missing five top row keys and one key from the next to the top row. I think Kevin needs the keys worse than I do though. But why do you have an LA36 keyboard to scavenge this from? (Where is the rest of the LA36?!)

Kevin,

Do send me a PM with a mailing address and I will put the eprom in the mail. I will send the very one in the photos. I don't need it and have plenty of 2716s. There are no details to discuss, just send your address.

I desoldered one side of the jumpers in my terminal, because I intended to return it to original condition (because the terminal worked fine before.) You could just cut yours, if you wanted, or you could desolder one end and fold up like I did.

Lou

MikeS
September 7th, 2010, 05:28 PM
Mike,

I looked at your picture of the plunger and thought "what the heck is that box on the side???" So, I went out to the garage and pulled a key on my LA36. I happened to pull one from the small keypad on the left. I pulled the one for 110 baud, and it had a little box on the side like yours! But, I spotted right away that the side box and wire hook are the mechanism that holds the key down (like caps lock). So, I pulled a key with a normal spring back action (I picked control), and it looks like a "normal" plunger like the one in my blurry photo. Not really, Lou. That plunger is from the "HERE IS" key, which is a momentary key, and the slot for the wire hook is straight up and down and only serves to keep the key from flying off. The latching key stems have the same little box but it has a V-shaped slot like most latching buttons use, where the wire alternately goes in one groove or the other. I don't have the actual keyboards, just the 8-key control pads on the left.

I've got a few LA-100s that I'll be scrapping but they're also RO models and probably the same type of keys.

I think I may have some other keyboards that use that mechanism though; with a little luck I'll find something compatible. ISTR that some AIM-65 keyboards used those; I don't suppose it matters if they're white?

m

Lou - N2MIY
September 7th, 2010, 05:43 PM
Mike,

Interesting. The design of keyboard you have may then be older than the one in my LA36 (or at least the main keyboard part of it.) I would bet that even though the plungers are different, the keycaps still fit the same.

Sorry to hear about scrapping out LA100s. I have one of those without the keyboard (printer only). When I got it, I tore it down, cleaned it, and restored it. Of course, it never gets used and is in a closet. If and when you come to that sad event, there are some parts I could use to restore my LA34 (namely the clear plastic shield that goes on the hinged front cover and parts of the tractor feed option, if you have them). I don't have any of the LA100 font rom cartridges either, that could be amusing for an hour. The LA100 keycaps are definitely the same vintage as the VT100 keyboard.

As for keycap color off any of your other keyboards, that doesn't matter. It's nothing spray paint can't fix.

Lou

MikeS
September 7th, 2010, 06:09 PM
I think you misunderstood: I don't have any main keyboards for the LA36 or the LA100, just the control keypads.

But I think you're in luck. I found 4 different keyboards using those plungers (and another bunch using different ones; amazing how many different types there are).

Same length, but no box on the side; just slots and a couple of little barbs.

Also a few matching keys with no legend at all, roughly the same colour as the LA36 keys.

I assume you have the springs? (They're all different too ;-) )

4422

Let me know what else you can use off the LA-100s; yes, they all have tractor feeds.

Want a service manual and/or documentation package?
Tips on how to use it with a hardware-handshaking PC? Remind me to tell you a funny DEC story about that...

PM me and we'll work out the details.

m

Lou - N2MIY
September 7th, 2010, 06:30 PM
Mike,

You are correct, I did misunderstand about the keyboards. I'm glad though that you saved what you did.

The boxes with the slots and barbs are exactly what I see in the VT100 keyboards.

The springs don't get lost unless the plunger is removed, so we're good on springs.

Lou

MikeS
September 7th, 2010, 06:56 PM
Mike,

You are correct, I did misunderstand about the keyboards. I'm glad though that you saved what you did.

The boxes with the slots and barbs are exactly what I see in the VT100 keyboards.

The springs don't get lost unless the plunger is removed, so we're good on springs.

LouJust checking JIC.

So, after all that you don't need any plungers, just 3 keys and whatever else off the LA-100?

MikeS
September 7th, 2010, 07:52 PM
Way back before half the kids on here were born I was replacing some systems that used XON/XOFF serial protocol to talk to DEC LA-100 printers with those new-fangled IBM PCs. Of course as we all know (don't we?) PCs don't natively talk XON/XOFF but use hardware handshaking on the serial ports; alas, LA-100s only speak XON/XOFF. There was a vague mention in the tech manual suggesting that it might be possible to enable HW handshaking, but absolutely no clue how, and no jumpers anywhere.

Seemed simple enough; phoned all the local DEC folks and third-party service outfits, but after spending the better part of the day laboriously explaining again what I wanted, no one had an answer.

Finally decided to call DEC in Maynard and a charming young lady answered the phone (some of us old-timers still remember those days long ago when real people answered "switchboards"). I asked to speak to someone about an obscure LA100 tech issue, but instead of transferring my call she asked me to explain what I wanted to know. Great, I gotta waste another half hour explaining before she transfers me and I get to explain it all for the twentieth time... No, before I got half way through she had the answer for me; "no problem, just cut the trace between a and b and run a jumper to pin x on IC z."

I was speechless; after getting nowhere with half the DEC experts in Canada, the DEC switchboard operator knew the answer???

(Turns out one of the printer engineers happened to be standing beside her and had overheard the question)

OK, so it wasn't very funny; ya had to be there ;-)

iprefermuffins
September 8th, 2010, 06:44 AM
Hmm, I'm still a little unsure about the shape of the keys themselves. The VT1XX keys have a semicircular cutout on the longest edge of the "stem" (you can kind of see it in Lou's pic here (http://www.vintage-computer.com/vcforum/album.php?albumid=51&attachmentid=4405)) which I don't really see in Mike's picture. The overall shape of the key and the stem look a little different too.

For what it's worth, the keys on mine seem to have a white base/underside with a black cap on top covering the normally-visible part of the key.

Mike, I'm one of "the kids" - this VT102 was assembled a few years before I was born. I picked it up intending to mess around with it, maybe try connecting it to a Linux box as a serial terminal (which I still plan to try if I can resolve the scrambled characters). It's really interesting to see the amount of technical documentation available on equipment from a few decades ago, and how much of it was designed to be user-serviceable.

EDIT: Also wanted to mention again that I also got a VT240 (needs work), VR201 monitor, and LA50-RA printer, all of which I want to give away. I'll be moving in about a month, so unfortunately I'll have to throw them out if I don't find any takers by then (I'll also try listing them on Craigslist soon). I'm in Marlborough, MA.

Kevin

MikeS
September 8th, 2010, 03:16 PM
Hmm, I'm still a little unsure about the shape of the keys themselves. The VT1XX keys have a semicircular cutout on the longest edge of the "stem" (you can kind of see it in Lou's pic here (http://www.vintage-computer.com/vcforum/album.php?albumid=51&attachmentid=4405)) which I don't really see in Mike's picture. The overall shape of the key and the stem look a little different too.I don't know if the shape of the stem actually matters unless there's something at the very bottom of the switch assembly that needs clearance; the keys just go into the plunger until the top of the plunger bottoms under the key. Maybe Lou can compare the VT keys to those on the LA36 control panel, so I have a reference.
For what it's worth, the keys on mine seem to have a white base/underside with a black cap on top covering the normally-visible part of the key.Those are called "double-shot" keys; the legend is actually molded into the key so that it doesn't wear off as the key top wears down.
Mike, I'm one of "the kids" - this VT102 was assembled a few years before I was born. I picked it up intending to mess around with it, maybe try connecting it to a Linux box as a serial terminal (which I still plan to try if I can resolve the scrambled characters). It's really interesting to see the amount of technical documentation available on equipment from a few decades ago, and how much of it was designed to be user-serviceable.Hey, once you pass 65 you can call everybody a "kid" ;-)
Yeah, thanks to a lot of generous (time & $$s) individuals, there is an amazing amount of old documentation still around; unfortunately a lot also seems to have been lost...


EDIT: Also wanted to mention again that I also got a VT240 (needs work), VR201 monitor, and LA50-RA printer, all of which I want to give away. I'll be moving in about a month, so unfortunately I'll have to throw them out if I don't find any takers by then (I'll also try listing them on Craigslist soon). I'm in Marlborough, MA.

KevinHope you find a taker; I've also got printers and terminals that will probably go to the dump for lack of interest...

Lou - N2MIY
September 8th, 2010, 05:47 PM
Ok, the LA36 keypad keys are not as tall as VT100 keys. I have the LA36 "here is" key in my hand at the moment. They also fit slightly loose in the VT100 keyboard, but the loose part can be fixed with one layer of scotch tape. I would still be happy to use them as a replacement. Let's face it, these keyboards see occasional use anymore, so little things like wrong key height are a trivial nuisance. The semicircular cutout in the VT100 keys are unimportant.

Double shot keys. That was when stuff was made to last FOREVER.

I, for one, am quite grateful that the dec documentation is as fine as it is. This is one of the key reasons why dec hardware still has the following that it does. We who care can keep it running. The restoration story of the pdp-1 at the Computer History Museum is an awesome testament. (and yes, I went to see it in person.)

Lou

iprefermuffins
September 10th, 2010, 04:05 PM
Got the chargen rom in the mail from Lou today...and it works! Thanks Lou!

Now to find a cable/adapter and see if I can connect to a computer with the terminal...

Lou - N2MIY
September 10th, 2010, 04:48 PM
Gentlemen,

We can all feel good today. We have done our part to keep vintage gear running! Have an extra beer this evening!

Kevin,

Please post a picture of your VT102 so we can bask in the glow of the CRT.

Lou

iprefermuffins
September 12th, 2010, 10:08 PM
Here we go:
448144834482

Much better than before!

Kevin

RickNel
September 24th, 2010, 08:12 PM
Lou -

I just caught up with your post of Sept 4 about chargen replacement cuts and jumps. Can I take you up on the offer of photographing the chargen replacement mod for the VT100? I still have the chargen from the code you sent me months ago, but have not got it running properly yet.

As to my VT100 power supply - no progress since our last exchange. I have just in the last two days finally got my S-100 machine running, so am turning my mind back to the terminal.

Probably I will have to build a replacement PS from a modified AT power supply unless/until I find some local assistance (Canberra, Australia) with that stubborn PS fault. Producing that weird -23v rail is the only obstacle.

Rick

Lou - N2MIY
September 25th, 2010, 04:29 AM
Rick,

Sure thing, I will work on it (VT100 mod) some evening next week. I haven't actually done it yet, but I know I can. I will need to make another rom, since I mailed Kevin the one I made last time.

Sorry to hear about your power supply. Oddly enough I was having e-mail correspondance with one of your fellow countrymen for a few months about a VT100 power supply. We could never get his working either. I seem to have much better chances when the supply is on my own bench vs. diagnosing remotely. Hopefully you find some help down under. I know there are fellows who read alt.sys.pdp11 that might be close enough to you to be of help.

Lou

Lou - N2MIY
October 7th, 2010, 05:44 PM
Ok, and now as Rick has requested, here is the mod to replace the chargen rom in the VT100 with a 2716 in the alternate rom socket.

http://www.vintage-computer.com/vcforum/album.php?albumid=58&attachmentid=4647

See that this mod is simpler. Cut jumper W1. Prepare the rom the same way as for a VT102 and plug it in. Then you are done.

Lou

RickNel
October 23rd, 2010, 03:14 PM
Thanks Lou - I'll do this as soon as I get power supply fixed.