Vintage CRT Monitor Repair Thread

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

  1. sean0118

    sean0118 Member

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    As some of you already know, I recently picked up a couple of vintage CRTs from hard rubbish/council clean up. There were at least 20+ other vintage monitors, but they had all been smashed for the collection of scrap copper...

    It's important to mention that CRT monitors use dangerously high voltages (~25000V) and can store charge even when unplugged from mains power. ;)


    First up is the IBM 8513003 from 1990:

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    It looks in good condition except someone has cut the display cable off the back! Now I have to work out what type it is and replace it. :mad:

    I *think* it's probably just a standard VGA?


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    I removed the power supply and inspected it before powering the monitor up. The epoxy used to protect some components against vibration was starting to corrode the legs of the larger power resistors, luckily it chipped off easily.

    I also measured the voltages on the power supply outputs, I couldn't find any documentation on what they should be, but they seemed resonable. Interestingly they were low voltage AC (~7.5V from memory) and mains. I would have expected DC from working on modern power supplies. When I have some time I'll have a closer look at this power supply and try to work out it's operation.

    I couldn't see any issues, so I put it back together and powered it up and.... it verks!!! Well it displays a white screen which is a good start... :D


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    Next is the Topcon 14HP34T from 1989:

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    It's quite an interesting looking monitor, but I couldn't find much information about it online, all I found was:

    "CRT : Paper White, Amber, Green 14" Monochrome Monitor Model 14HP33T/14HP34T"


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    It uses a CPT branded monitor,as far as I can tell CPT still produce (LCD) displays.


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    It also had its cables cut off! The mains cable is easy for me to replace, but the display cable will be tricky unless someone on here knows what type it was.... Also what's the function of the INV / NOR switch? I might be showing my (lack of) age here... :confused:


    Still to come is the Amstrad PC-MM, I'll update the thread with details soon. It has quite an ***interesting*** electrical design... :Paranoid:

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    Last edited: Nov 13, 2016
  2. JidaiGeki

    JidaiGeki Member

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    Such a shame, these really old CRTs (12"/14"/15") are getting very rare - especially the PC ones which were junked mainly in the 90s/00s. In my recent experience 108x Commodore/Amiga monitors are now much easier to get hold of.

    As you've probably discovered it holds the power supply for an Amstrad PC1512/1640 computer. I've got a PC1512 with the PC-CM CGA version of this monitor.


    Click to view full size!
     
  3. elvis

    elvis Old school old fool

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    I don't understand why people cut cables off. Is there some sort of rule about electronic waste that folks have to do this? Or is it just one of those stupid things that someone started, and now everyone copies without thinking?
     
  4. Kafoopsy

    Kafoopsy Member

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    It's done by people collecting copper. I've never understood why as the money they would make from it would barely cover the cost of fuel driving around collecting it. Data cables especially would have diddly squat copper in them anyway.
     
  5. elvis

    elvis Old school old fool

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    Nah, this is different. Copper vultures usually go for the yoke on the back of the tube, as there's tonnes more copper in that. That makes me even more mad, because then then the lead-lined tube generally ends up in landfill as folks don't bother to re-use the CRT at all.

    I'm talking about people who snip the cables before they thrown them out. I see it a lot around my neighbourhood on kerbside collection day - folks putting them out like that. I've never been able to chat to someone and ask them why.

    Googling about, people claim the council tells you to in order to stop people plugging in bad appliances and burning their houses down. But there's absolutely nowhere on any council website that I've come across that says this. Seems to be an old wive's tail.
     
  6. shane41

    shane41 Member

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    They'll snip the cables if " they can get away with it "
    ie. Quick snip, gather some copper & off they go.

    I've seen it first hand. They don't want to be seen doing it & will easily fade away from view.

    That professional " take it all " rear cover comes off, does his vandalism & cover goes back on. Wee Ben remember his video's he was so proud of :thumbdn:

    edit. There's also the owner who may take the lead for another use. Add a female plug & make a complete lead.
     
    Last edited: Nov 13, 2016
  7. )(arg0n

    )(arg0n Member

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    I have seen many guys pull up in old beaten vans or station wagons, snip the cables then drive off all in about 15-20 seconds. I'm with the comments above, surely it couldn't be worth the effort or time and fuel but it happens a lot unfortunately.
     
  8. elvis

    elvis Old school old fool

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    Well anyways, I'm pretty sure everyone in this forum agrees copper vultures are terrible. Let's get back to the much more interesting topics of repair and reuse.
     
  9. OP
    OP
    sean0118

    sean0118 Member

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    I'll have to keep an eye out for more then. Although I only have limited storage space... hint... hint... ;)

    Interesting! I didn't notice that, although I haven't looked closely at it yet. I did see that the metal of the case isn't earthed which I find very unusual.

    PC-CM is the colour version of the PC-MM right?

    It's both, council 'rules' and people collecting copper. It's a shame, I can replace cables but repairing broken tubes is a bit beyond my capabilities. :p

    I always thought it would be impossible to repair a tube once the neck is broken, but after watching the following video I'm not so sure:

    https://youtu.be/W3G7b-DcOO4?list=FLmn5D17KMm9R3XhfXFDGmnA
     
    Last edited: Nov 13, 2016
  10. partybear

    partybear Member

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    I used to help a guy I worked with collect copper sometimes. He would go nuts for cables, but honestly I don't remember him going into any monitors I don't think he knew copper was easily gotten from them so he would just collect the cables. He had a sweet rig in his shed to peel all the insulation off them.
     
  11. JidaiGeki

    JidaiGeki Member

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    That's right, the CM is CGA, the MM is mono. The monitor will likely have a proprietary video connector so you won't be able to hook up a conventional PC. The CGA version has three cords coming out of it (8 pin video signal, power in, power out 10 pin to the computer, based on my setup) so if you're missing any of those cables it might be game over ...
     
  12. OP
    OP
    sean0118

    sean0118 Member

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    Yes, that might be a major problem then, I don't like the sound of these proprietary connectors. :(
     
  13. elvis

    elvis Old school old fool

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    Connection cables are the easiest bit to make. No high voltage dramas, and signals usually conform to a particular standard.

    I regularly make cables and converters that change signals between RGB/SCART for TVs, computer VGA signals, or the higher power signals required for arcade monitors. There are tonnes of specs online, and generally simple circuits with the correct caps or resistors in place will give you the voltages and loads needed to be within spec.
     
  14. )(arg0n

    )(arg0n Member

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    Yeah I couldn't agree more. I have a nice LG Flatron T910B here thats starting to squeal occasionally. Real pity because its a really nice monitor. I'm guessing flyback transformer? I looked around for repair advice a few weeks ago and looks like I just have to find a spare one from a working monitor, that sux, not really a servicable part. Still got lots of life left in it though, I'll just have to keep adjusting the refresh rate when it starts to annoy me :rolleyes:
     
  15. JidaiGeki

    JidaiGeki Member

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    Fair point, and hopefully Sean can get this one up and running again.

    The pinouts for video and power are on the bottom of this page:

    http://www.seasip.info/AmstradXT/1512tech/section1.html

    Worth noting that Amstrad in that era did have a few non-standard quirks with its hardware eg non standard keyboards.
     
    Last edited: Nov 14, 2016
  16. elvis

    elvis Old school old fool

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  17. )(arg0n

    )(arg0n Member

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    saved a LG Flatron T910B off the street today. Exact same model/colour as the one I have. Beyond the cord being snipped and a rattle inside of it seems to be in reasonable condition, will open it up when I get a chance and inspect :)
     
  18. OP
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    sean0118

    sean0118 Member

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    These are the first CRTs I've ever repaired, but I think any magnetics can squeal, so the deflection yoke and other transformers/inductors could be the culprit too.

    I suspect a failed capacitor could also be the cause of squealing (in the magnetics) due to a loss of filtering etc.

    Also, be very careful with the flyback, don't assume it's discharged when off. ;)
     
  19. )(arg0n

    )(arg0n Member

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    ok cheers. I did a lot of reading a few weeks ago in the hopes it would be an easy fix. I'll put it in the 'if it ain't broke don't fix it' basket for now (nothing wrong with it bar the noise). As above though I found an identical one on the street today minus the vga cable - could be good for spare parts? I'll try and sort a new cable for it and test it first anyway just for fun :)
     
  20. DonutKing

    DonutKing Member

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    With squealing, I find the best way is to get a cardboard tube from a roll of paper towels, take the cover off, turn the CRT on and listen through the tube to pinpoint the noise... being careful not to touch anything on the live chassis of course :) This way you can identify any individual components making the noise.
     

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