Help wanted with monitor

[sirseand]

I have a desperate need for help with regards to a piece of industrial equipment.
Those of you that get a buzz out of old-style computing will be glad to know that there is a lot of equipment around that rely on some really old school computers for control. In my case a Spark Eroder that is in daily use in a tool room.
My problem is the screen. The original industrial screen was changed before my time at this place with the one shown in the attached photos. Have had this unit repaired by someone is a wiz with modern electrical controls, but he admits that his knowledge base is lacking in this area.
So currently I am looking for a replacement Mono screen and or the help of someone who knows about these things as I am way out of my depth.

Thanks.

[SpidersWeb]

I'm guessing the software was written specifically for a 720x348 MGA display. (If that's not the case, I'd just use a VGA card and display).

For commercial purposes, my recommendation would be to get on ebay and order a brand new one. Because of old systems like this, they actually produce new LCD flat screens that are monochrome and connect to a mono card like yours.

See here http://www.ebay.com/itm/New-9Pin-Monoch ... 2ea4e1b0a7

For the enthusiast, it's too high in price and not authentic. If price was a big factor, then I'd recommend finding someone who has been repairing TV's for 30+ years. Most electronic repairers are becoming a bit beyond the CRT TV generation - but I managed to find one here in Wellington - a tiny shop in the suburbs - who was able to diagnose my IBM 5151 mono display before he'd even opened it. Took him 30 minutes to repair, but for some reason took 3 weeks to find those 30 minutes lol Worth the wait though.

Edit: that's just my 2 cents, someone else may have better ideas

[Gibsaw]

Yeah, I'd agree. If this isn't VGA, and it's green screen, then I'd almost certainly hang my hat on it being MDA/Hercules.

Also, I would definitely try out an ordinary VGA. (obviously you'll need to track down a 16bit VGA card) If the software isn't written for Hercules specifically, then that would be your simplest course of action.

[SpidersWeb]

Yeah it's definitely MDA - you can tell by the missing pins on the DE9.

1 Ground
2 Ground
3 Not connected
4 Not connected
5 Not connected
6 High intensity
7 Video
8 Horizontal sync
9 Vertical sync

Question becomes why did they pull out a VGA adaptor (ref: PC sticker shows 512K VGA card was originally in it) and throw in an old 8 bit MGA/Parallel.
Fingers crossed it was because they didn't want to buy a new screen.

Edit: apparently some VGA cards provided MGA emulation in hardware - I have some that I'm suspicious may be capable - I'll try and make time to play with them in the weekend.

[SpidersWeb]

Experimenting with alternatives now. I've got Western Digital's tool for setting card modes, just going through the cards. The MDA, MGA single page, and MGA full options are greyed out on the first two cards I tried. CGA hardware emulation worked well. Going to go dig up more cards now, see if I can find an MDA->VGA solution.

[sirseand]

Thanks Guys.
I am already feeling more confident. I see the one on E bay is running in at NZD542.34. Quite a bite but not unreachable. Just have to make sure it's going to work and find out how long it will take to get here.
I know that the screen shown was a replacement for the original industrial unit that it had, however I very much doubt that cards, and even more so software was changed to accommodate this.
It does use specifically designed software, (only one application) off a DOS platform. What version I don't know.
I have been looking at this article which I can source from a guy in Blenheim.

http://www.arcadomaniashop.com/epages/e ... ViewAction

Just not sure if it is a workable alternative. Have you guys any experience with this converter. Can't get much info from the vender apart from what you see there.

[SpidersWeb]

That adaptor is for RGB/CGA/EGA - not MDA/MGA/Hercules (whatever you want to call it) which is what that display is - 720x350 monochrome. You can tell because the 3 pins that are missing are what CGA and EGA units use for sending colour signals. Hercules Graphics were quite popular through the 80's because it provided high resolution and crisp text at a fairly low price. This one does support MDA - http://www.ebay.com/itm/Brand-NEW-MDA-R ... 3a67e41129 (and CGA, EGA etc) and is a bit cheaper than the LCD (but still pricey enough that I haven't tried one).

I was able to get my VGA cards (4 x Western Digital, 1 x Trident 8900CL) to emulate hardware CGA perfectly, but their was weird issues with MDA and MGA emulation so I can't recommend that until I work out what's going on.
Do you have any spare old PC gear lying about to do testing with? If you had a VGA card lying around it might be worth swapping out the mono card for it and just seeing what happens.

[sirseand]

Thanks for all your efforts. I am hesitant to try these things myself given that what I know about the system is dangerous. I don't have any old gear which perhaps fortunate as I know I would be tempted! The link you supplied looks like the way to go. Just have to convince those that pay the bills that it is.
I have an unopened original DOS 6.22. Pm me with your address and it's yours. Thanks again SpidersWeb.

[SpidersWeb]

Quick update for anyone who is curious.

sirseand kindly passed me a sealed copy of MS DOS 6.22 and the monitor itself once his replacement arrived, and over the last couple of weeks I finally pulled it out and tested it.

To start with I got this:


I discovered this monitor also goes by the names Hyundai HMM-1200, and Commodore 1402.. which led me to the hsync circuit


I went to an electronics forum and they pointed out that all of the horizontal deflection power goes through C505 and if that was faulty (or anything else in that bit), I'd get that problem.
I went through and checked continuity / behaviour of each component in circuit then started de soldering and testing caps.

Firstly if we look at C505 we see a problem I should have jumped on immediately:

If you compare it's size to the PCB circle - you'll see it's clearly not an original part and likely insufficient for the job at hand. I also matched it's photo to the jaycar website (although they sell a different model now) and various Alibaba/Aliexpress type sites - it's a no datasheet + made in china type deal.

I removed it, and tested it as being 1uF (10% of it's original value).
I replaced it with another NP electrolytic - and tada - perfect display!

Unfortunately I don't have a photo, because I shorted the board by accident afterwards (I'm special sometimes) and took out the fuse. I'll grab a new one on Saturday when I'm out.
Also my replacement cap, is also too small and is not going to last much more than a few minutes at a time - I'm waiting on a proper replacement designed for this application to come over from the US.

[SpidersWeb]

Got the new cap in:



and tada:


There is a bit of screen burn, and the picture displays on a slightly angle but in text mode DOS you barely notice. Good little spare Ran for an hour last night without any smoke, weird noises, or explosions.

[Carcenomy]

OH FOR CHRISTS SAKE THIS IS WHY I SHOULDN'T GO AWAY!

I have a bloody Commodore 1402 sitting on a shelf next to the PC10. It works 100%. Dude coulda had it.

[SpidersWeb]

LOL you should certainly stick around!

[Carcenomy]

Life's been a flaming abortion as of late, finally starting to settle down again so I can pay attention to things like my hobbies