Connecting CPC 6128 to Samsung Syncmaster monitor

[Jonathan]

If I can't get the CTM-644 fixed, the second best option would be to attach the computer to a spare monitor.


It's a Samsung SyncMaster 920NW 19" 1440x900 Widescreen LCD Monitor


Currently it's in the garage but the manual online mentions it having a 15-pin D-sub port.


Would it be possible to connect it up?


I guess I would also need a 12V power source for the CPC itself.


Thanks again in anticipation!

[tjohnson]

I don't think VGA monitors will work, VGA uses seperate H and V sync while the Amstrad uses a composite signal.  I also think monitors rarely supports 15Hz refresh as VGA is 31Hz, some older monitors do but not many.  I could be getting the refresh thing mixed up though.  Your best bet is to find an old CRT with scart or an LCD with scart.

[pelrun]

Often RGBHV inputs will accept composite sync just by connecting it to the Hsync input. I have a Dell monitor that supports 15khz video, and has no problem accepting the CPC monitor output directly.

http://15khz.wikidot.com/ has a partial list of monitors and whether they work or not. Some SyncMaster models are listed as having partial 15khz support (the 920 doesn't have an entry unfortunately), so there is at least a chance it might work.

[Jonathan]

Thanks. This sounds (sort of) promising. What cable/converter would I need?

[tjohnson]

You'll need to make up a custom cable 6 pin (CPC) or 8 pin (Plus) cable to VGA to try it.  Look up the signals on the interweb and get the soldering iron out.  Probably best to buy a VGA cable, cut one end off, then solder respective wires to the din plug.

[Jonathan]

Thank you. I've not had a soldering iron for years so unfortunately this isn't something I'll be doing in the short term!


I wonder whether anyone on the forum would consider selling a cable...?

[eto]

If your monitor doesn't support 15kHZ, the cheapest way of doing it is a GBS 8200. Explained here: https://www.octoate.de/articles/connect-cpc-to-vga-display/
Just make sure to turn the RGB resistors to the minimal setting, otherwise the image will be too dark. You can get the GBS on Amazon or Ebay really cheap. For me it works well, however it doesn't work in some games/demos which are playing with the CRTC, e.g. Ghosts'n'Goblins is hard to play as the screen goes berserk when it scrolls.

If your monitor supports 15Khz you might be able to connect it directly. I ordered this little device, which splits csync into hsync and vsync and worked for me on a 15KHz capable TFT: https://www.arananet.net/pedidos/product/cpc2vga-sync-converter-for-cpc-6128/ Unfortunately out of stock right now.

However, I am not 100% sure if it's really required to split csync as at least according to the specs, pin 13 of the VGA connector should also accept csync. But I couldn't find anything about this on the net. if it works, you can basically build a cable for almost nothing. Just take an old VGA cable and solder it to a CPC monitor connector.

Another cheap option, which was mentioned somewhere, is a SCART to HDMI adapter/upscaler. But I haven't tried that yet and don't know if it's working well or not or if it would be compatibly with a HDMI to VGA adapter.

[Sid_]

I've got one if you want it.
I can't use it on my screens (they don't support the 15khz).

[Jonathan]

I've got one if you want it.
I can't use it on my screens (they don't support the 15khz).

Mega. Worth a try. How much would you like for it? Could we arrange this by private message? Thank you.

[Sid_]

half of the price  and shipping fees it's ok for me.

[Jonathan]

Sid has kindly send me a connector (the one from the Arananet website) - thank you very much.


It occurred to me that the CPC 6128 and its disc drive will still need a power source. I could keep using the old CTM-644 for that but is there a better alternative?

[tjohnson]

It's a bit of a pain as you need 5v and 12v and I think the 12v is centre negative from what I recall so it will be a bit of fiddling about to get a tidy solution for both voltages I had to make up a solution using a buck converter to provide both voltage from one psu.

[Jonathan]

Thanks. If I can't get the old monitor fixed then the long-term solution is probably a replacement. In the short term if Sid's connector works with the Samsung monitor then I'll likely just set them side by side.

[tjohnson]

Thanks. If I can't get the old monitor fixed then the long-term solution is probably a replacement. In the short term if Sid's connector works with the Samsung monitor then I'll likely just set them side by side.

Let us know if the cable works please.  Cheers Trevor

[Jonathan]

Let us know if the cable works please.  Cheers Trevor

It has arrived safely, but I've been advised that my wonky CTM-644 is a fire hazard. Before buying a separate power source for the CPC (which I hadn't originally thought about) I'm going to see if the CTM-644 can be fixed. So I'm a step closer but don't know yet. I'll update the http://15khz.wikidot.com/ page and this topic when I find out. If it doesn't work I'll pass the adapter on.

[pelrun]

but I've been advised that my wonky CTM-644 is a fire hazard.

If the only issue is the gun convergence being off and there's no obvious damage to the power cable, then that's a very suspect claim.
Edit: apparently the person giving the advice is an experienced CRT technician and had more information about the exact nature of the problem, which isn't something I knew when making that comment. Ignore me!

[Bryce]

If the only issue is the gun convergence being off and there's no obvious damage to the power cable, then that's a very suspect claim.

Not really, the repairer suspects that the deflection coils could have damaged insulation (entirely possible and a common fault) which would be a fire hazard.

Bryce.

[Jonathan]

If the only issue is the gun convergence being off and there's no obvious damage to the power cable, then that's a very suspect claim.

The fellow on Amibay (the forum that Bryce put me onto) suspects it's a short in the deflection yoke.


He reckons there is a slim chance of fixing it, but if he manages it then he'll charge £35-50. They call him the "CRT King" on that forum so I am happy to trust him!

[Bryce]

I know Roy a long time and he knows his stuff. He has saved many CRT's over the years.


Bryce.

[Jonathan]

I know Roy a long time and he knows his stuff. He has saved many CRT's over the years.


Bryce.

I'm going to carefully package and post him the monitor ASAP so it's good to hear this! :-)

[tjohnson]

Tried the cable yet? Did it work?

[Jonathan]

Not yet. I'll post here as soon as I get a chance. I need to send the old CTM-644 off for repair first. When I got the adapter I hadn't really thought through the fact that the broken monitor was the power source for the CPC...

[tjohnson]

You can plug the monitor into the cpc without using the din socket as a test

[Jonathan]

I would get in trouble if it went on fire :-)

[tjohnson]

Find a 5v power adapter knocking around,  centre positive, check it has 1a rating and test it.  Your drive won't work as this needs 12v centre negative but you'll get a picture.