Vintage CRT Monitor Repair Thread

Discussion in 'Retro & Arcade Worklogs' started by sean0118, Nov 13, 2016.

  1. elvis

    elvis Old school old fool

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    Great tip. Never thought of that. :thumbup:
     
  2. callan

    callan Member

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    I recognise the Topcon monitor: I used to sell them back in the late 80's.
    You'll find it's an IBM MDA monitor. (DB9 TTL)
    From memory the invert /normal switch inverts the video signal, making it white on black, or black on white.

    These came in various flavours, so I can't be sure: but some were multisync insmuch as you could plug them into an MDA/Hercules card and get a nice monochrome output, or plug them into a CGA card and get a shitty pseudo-grey scale output from interpolation of the digital CGA input. (They autoswitch). They worked well with auto-switch MDA/CGA cards of the vintage - you could switch using "mode co80, or "mode mono" and the monitor would switch with it. Not all could manage it, though - some were MDA only.

    You got the runt of the litter - the paperwhite. The phospor of the paperwhite A: badly suffered REALLY BADLY from burn in and B: had differering persistence phospors that blend to make the paperwhite display, resulting in a screen that kinda turned pink when text scrolled (the reddish-phospors had longer persistance than other mixed colours) Looked freaky.

    I can't tell you much more about them other than that they were not terribly reliable.

    Callan
     
  3. OP
    OP
    sean0118

    sean0118 Member

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    Yep that sounds right, I've found the same model online (link) re-badged with the Intra brand. They are listed as IBM MDA 18.432 kHz and CGA 15.75kHz compatible.

    That's interesting with the INV switch, I thought it might flip the image upside down, but inverting the colours makes a lot more sense!

    How do you identify that it's paperwhite? I was hoping for green/amber... :upset: :p
     
  4. callan

    callan Member

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    Sorry - I thought you'd mentioned that it was paperwhite - I misread your post.
    I honestly don't know which phosphor it is, TBH - simplest is to power it up once you've wired in some sort of power cord (just turn up the brightness - it'll display some sort of a raster even without input)

    Judging from the internal reflection from your camera flash it doesn't look like there is as much burnin as I've see, so you might be lucky.

    Callan
     
    Last edited: Nov 18, 2016
  5. )(arg0n

    )(arg0n Member

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    Saved from the street, needs a new vga cable and something was rattling aorund inside so started pulling it apart to see what I was dealing with (never dismantled a CRT before).


    Click to view full size!



    Click to view full size!


    Lots of dust inside which was a little surprising given theres no fans moving dirty air around and the ventilation openings are pretty small. It looks like there has been a little bit of moisture in there too, enough to make the dust clump up but not cause any rust (could have been on the street for a few days dunno).


    Click to view full size!



    Click to view full size!


    I only have an anti-static brush to try and clean it but it did alright


    Click to view full size!


    I don't have anything to make a spare cable atm but really wanted to see if it was working. I already have one of these monitors and remembered it has an OSD come up if the VGA cable is not attached.


    Click to view full size!


    That message box changes between green, red and blue so the colours all looked fine. Although, compared to my previous one there is def a yellow tint to the image, the colours are not as rich. Something to look into further when I get a cable made up. Could just be internal monitor settings but I can't bring up the menu if the vga is disconnected. The rattle turned out to be two broken plastic clips so nothing to worry about there :).
     
  6. elvis

    elvis Old school old fool

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    Aww yiss CRT porn. Keep 'em coming.
     
  7. 0xC0FFEEADD1C7

    0xC0FFEEADD1C7 Member

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    That's not moisture damage that's causing the dust to clump up. That monitor belonged to a heavy smoker, I can guarantee it. It's tar.

    I see this quite a lot in my work.
     
  8. OP
    OP
    sean0118

    sean0118 Member

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    The replacement VGA cable arrived for the IBM 8513 so I got started repairing it:

    [​IMG]

    I reused the connector and other components from the original cable stub...

    [​IMG]

    Luckily the strain relief could also be removed from the old cable...

    [​IMG]

    Next, I cut out a section of insulation from the new cable, this is where the earthing lug goes. It's notable that the original IBM cable had both a foil shield and a thick metal braid, the new VGA cable is a different design and only has the foil and some copper wire.

    [​IMG]

    I padded out the cable with some foil so that the shield makes contact with the earthing lug (I later re-did this with a longer piece of foil).

    [​IMG]

    Next it was time to connect the wires of the new cable to the old stub. I've made a document that matches the pinout of both connectors (IBM 8513 Pinout Table).

    It's interesting to note that the original IBM cable uses proper coax for the RGB video, with each video cable having a separate return/ground. The replacement cable uses the foil shield and bare copper wire as a common return for all three video signals.I suspect this is cheaper to manufacture and that most modern VGA cables are made this way.

    The short lengths of wire and being in a tight bundle made them difficult to join/splice. I taped both wires in place so I didn't have to hold them, then I lashed them together with some very fine gauge wire (these were individual strands from some scrap cable I have). They were then held in place and could be easily soldered (you should put something heat proof under this :lol: ). Each splice was covered in heat shrink to stop them shorting out against each other.

    The green wire on the new VGA cable went to pin 15, AFAIK pin 15 should not be connected to anything so I trimmed the bare copper off it's end and left it disconnected.

    [​IMG]

    The end result:

    [​IMG]

    [​IMG]

    The cable was almost ready to reconnect to the main board...

    [​IMG]

    But first I added some cable ties to the foil shield I made, this was to prevent the foil from tearing etc. It should work well but it looks super ghetto... :p

    [​IMG]

    [​IMG]

    It was then time to reassemble and plug in! And....



    It works!!! (of course :p)

    [​IMG]

    [​IMG]

    (I plugged the old laptop I used for testing into an LCD first so I could set the required display settings of 640x480 resolution, 60Hz)

    [​IMG]


    So I think we can call this one a success. The only issue I've noticed is that the image stretches slightly in the vertical direction when images with a lot of white are shown. E.g. the top tabs of FireFox are cutoff when looking at the Google home page... Is this normal?


    ;)


    (I tried to power up the Topcon but it's dead, I'll have a closer look when I get a chance)
     
    Last edited: Dec 4, 2016
  9. badmofo

    badmofo Member

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    Fantastic work mate :thumbup:
     
  10. OP
    OP
    sean0118

    sean0118 Member

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    It's hard rubbish season again and I got 'a few' finds...

    [​IMG]
    http://imgur.com/a/IjKms

    I hope they have some collector value. I got a 60" plasma as well... half way through repairing that... :lol:

    (The desk and sound system in the background also came from an earlier hard rubbish day)


    Anyway, I should be busy for awhile. I'll have to do an update on the Topcon monitor, I bought some parts to repair it recently. ;)
     
  11. callan

    callan Member

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    Good God! - NEC APC III's !!.
    Incompatible, quirky shits of things, but the HDD si a good one, and those floppy drives are brilliant. ?Teac 558's? - head load solenoids, direct drive, cast chassis, mod-able - and reliable. If they're not water damaged they'll likely still work!.
    The NEC Powermate1 plus brings back a lot of fond memories, too: Just watch that the screws are non-magnetic!.

    And is that an HP Vectra/386???


    Nice finds. I don't think you'll get much out of the APC III's, but the Powermate and HP units may give you joy!

    Callan
     
  12. OP
    OP
    sean0118

    sean0118 Member

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    The APC IIIs are probably in the best condition of the bunch... I guess no one ever used them... :lol:

    Yeah it is a HP Vectra, not sure if 386 or not.

    There's also an Amstrad PC1512-SD there too, needs a lot of work though, hopefully I can get it running with the matching monitor I got earlier.

    Any infor on the NEC Astra? oh, and why the non-magnetic warning for the Powermate Plus? ;)
     
  13. mAJORD

    mAJORD Member

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    how the hell do you find that much gold in one hard rubbish tour!

    i think I need to move to sydney :/
     
  14. OP
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    sean0118

    sean0118 Member

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    I can't help it. :lol:

    I found the Ferguson and Commodore CRTs together with the Commodore keyboard. Then I went back to where I found the IBM/Topcon/Amstrad monitors last time, to find the place FULL of old computers. :p

    Thinking I had collected enough, I proceeded to avoid hard rubbish for a few days, however, the house across from us throw out the 60" plasma and I found the Pioneer CS-33A speakers walking home after dropping the car off for a service a couple of blocks away... also got a Q6600 system I forgot to mention... :leet: :leet: :leet:
     
  15. callan

    callan Member

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    The PSU is in the monitor I think - bit of an oddball design, that. Not quite as odd as Olivetti M24's, where the PSU was in the main chassis, the Motherboard was UNDERNEATH it, and the VDU monitor was powered off the video card, (in turn powered by honking-great thick low-voltage power cables from the pissy fragile-ass main PSU. )

    I've never, ever seen one (and I was an engineer at an NEC dealership for 7 years!) Before even my time there was an Astra line of minicomputers in the early 80's, but that doesn't look like it was part of that: some sort of synchronous controller?? Doesn't look workstation-ish. Can't really see.

    'Cause the fuckin' screws drop into the case when you're working around with the cards, and you can't pull the damn things out with a magnet. You don't forget these things after scrabbling around at the back of some some shithole truck depot with a torch, fixing a monolith comms card coated in tar and rubber dust, stinking of rats piss......

    Fun times.:sick:

    Callan
     
    Last edited: May 20, 2017
  16. OP
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    sean0118

    sean0118 Member

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    Interesting, thanks Callan.

    The Astra is in poor condition, no lid, there's even leaves in it. Uses an NEC D8086D-2, here's some pics:

    [​IMG]

    [​IMG]

    ^^^ What interface is that!? :wired:
     
  17. callan

    callan Member

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    I have no idea. Some ring-topology networking system, but nothing I've ever seen before.

    Callan
     
  18. pfrcom

    pfrcom Member

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    Looks like AS/400 twinax
     
  19. 0xC0FFEEADD1C7

    0xC0FFEEADD1C7 Member

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    I have that exact same Commodore CGA monitor, it belongs to my Colt. It's a rebranded AOC. It gives me a pretty bad headache when I use it.

    I had a nice rubbish find as well, for once. Came across this nice old Sony workstation monitor (rebranded as HP) the other day when I went to take another crap monitor to the dump. Was sitting face down on a pallette in the ewaste drop off area.

    Has 5 BNC inputs on the back, does sync on green. Nice trinitron. It had been sitting in the rain for a while. and it was filthy, so I took it apart and cleaned it up today and made a ghetto cable from a chopped up vga cable so that I could test it. It works brilliantly and it looks like brand new after spending ages cleaning it. Best find ever.

    I am going to make up a proper shielded adapter box thing to connect to it that has BNC inputs and a vga connector and various other connectors on it.

    Yuck dirty and wet:
    [​IMG]

    Ghetto ass adapter cable (the individual red/green/blue are separate shielded coaxes inside the VGA cable so it's not AS bad as it looks):
    [​IMG]

    Yay, it works:
    [​IMG]

    I need more space:
    [​IMG]
     
  20. OP
    OP
    sean0118

    sean0118 Member

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    Yes, good find, the NEC Astra range is even mentioned on the wikipedia page for twinax cabling (used for networking in this case).

    I wonder if this made it compatable with the larger IBM sysems? As Callan mentioned, its doesn't look like a work station, so maybe it's meant to be used with peripheral disk drives, printers etc of IBM System/36 or similar?

    Anyway, I might be starting to hijack my own thread with non-vintage CRT repair posts. :lol:

    https://en.wikipedia.org/wiki/Twinaxial_cabling#NEC
    https://en.wikipedia.org/wiki/IBM_System/36


    That's a very nice monitor, and it looks brand new now that it's cleaned. ;)
     

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