IBM 5155 with monitor (commmodore) 184S or Philips CM883

[maxtherabbit]

R, G, B on CGA is not TTL level

yes it is

 

[Benedikt]

I can confirm that my Commodore 1084 definitely works as a CGA screen.
It is connected to a Commodore PC20-III (a turbo XT) via the 8 pin DIN digital RGB input and is actually the CGA screen recommended in the PC's manual.
Technically, you can connect an RCA cable, too and then switch back and forth, but I get black and white composite, only, because I have the PAL variant.

All digital outputs on a CGA card have TTL levels, i.e. nominally 5V but actually closer to 3.6V because of how TTL works.
The simplest proper RGBI to SCART converter would consist of an EPROM with lookup tables, an 8 bit buffer and three 2 bit R2R resistor networks with load resistor, respectively.
It would be a refined version of the improvised adapter demonstrated in this video: https://youtu.be/vwKA1z8tg1g

 

[Eudimorphodon]

The simplest proper RGBI to SCART converter would consist of an EPROM with lookup tables, an 8 bit buffer and three 2 bit R2R resistor networks with load resistor, respectively.

A GAL probably makes more sense than an EPROM these days, unless you have tons of the latter lying about. It's also faster.

 

[Benedikt]

The big advantages of an EPROM is are that the logic behind it is so trivial that anyone can understand it and that it is typically large enough to hold several variants of the lookup table.
You could e.g. add a four bit encoder switch to the extra address lines to choose from 16 different variants of the four-color CGA palettes.

 

[Eudimorphodon]

The big advantages of an EPROM is are that the logic behind it is so trivial that anyone can understand it and that it is typically large enough to hold several variants of the lookup table.

A GAL really isn't rocket science either; a proper "brown-fixed" version of the RGBI palette can be expressed trivially and leave enough room for at least three or four alternate palettes. It's what the GGLABs CGA2RGBI does. Unless you "know a guy" a 15ns EPROM is a lot more expensive than a 15ns 16v8.

 

[Casey]

So what does all this mean if you have an old school 4:3 VGA monitor you want to plug into one of these converters? I have a 17" that's 1024x768 and a 19" 1280x1024.

 

[g4ugm]

Hi,
I wanted to know if I could connect IBM 5155 from CGA card to the commodore 1084S monitor or Philips CM8833, they are RGB (CGA) monitors, with the cable that is fine.

Thanks for your help.

The CM8833 should work just fine. It has TTL inputs. I used one many years ago with a Amstrad PPC1640.

 

[andromeda92]

I have received my MCE2VGA and it work like a charm with IBM 5155.

On the other hand it is indicated nowhere the position of the switch on or OFF,
we do not know in which direction it is ON or OFF,
suddenly I tested the switches at random, what matters is that it works.

 

[A-ko]

1) buy an IBM 5153 monitor, it's too expensive and you rarely find it.

You don't need an IBM monitor...literally any CGA or EGA compatible monitor will work.

 

[erikarn]

I actually run my 5170 PC/AT CGA off of a 1084S with separate analog/digital RGB. It's just .. more convenient to do that with my C128D underneath than to try and find more desk space for the 5153 monitor that I have here.