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Microvitec Cub 653 Monitor (Type 1456 Li2) - Pinout

spiceminer

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Mar 8, 2014
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Hi everybody,

I have here a British made Microvitec Cub 653 Monitor (Type 1456 Li2) with a 7 pin DIN connector at the back and I have no idea what signal could be used as input or what the pinout might be.

Could anybody help?

I know that there are many different inputs are supported for the CUB 653 series (analogue RGB, TTL, BAS,...) which is reflected by the Type number.

Thanks a lot and best regards
Stephan
 
My immediate thought was 'BBC Micro', but apparently there were non-Beeb models sold by Microvitec. This advert suggests your model was for an IBM PC (see the selection chart on page two of the PDF). It has the same type code as the Apple II model but with a different colour ROM, which suggests 4-bit (RGBI) TTL input, i.e. CGA.

The service manual doesn't give the exact pinout for the DIN connector, but if you're comfortable opening up the case you can trace the wires to the main board where the manual lists the positions for TTL and analogue RGB and sync.
 
It's a TTL RGB connection as standard - designed really for the BBC range of computers. I don't have access to the pinout right now, but can probably find it - just look for a BBC Model B / Master 128 monitor connection.

However, you can convert them to analogue 15KHz RGB really quite easily - I did one years ago and used it as an arcade/NeoGeo monitor.

View attachment CUB Analogue RGB Conversion.pdf

IMG_1663.jpg

Hopefully that will help you out.
 
Thanks a lot. Analogue RGB is now working if composite sync is available. In this case, the signal was directly fed to the monitor's main board (not using the small interface PCB). Video source was an Amiga in this case, giving a crisp and clear image.

I tried then to adapt a Royal/TA Alphatronic PC with TTL video. I get a decent picture, but the colors are totally wrong. The intensity input of the monitor was put in GND, as the Alphatronic does not have an intensity output.

Using an IBM XT compatible with CGA output gives no picture at all.

Does anybody have an idea whats wrong here? Can anybody give an advice if the jumpers of the PL103 link block are set correctly for TTL operation? Whats the purpose of the analogue input board?

Best regards
Stephan
 

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I tried then to adapt a Royal/TA Alphatronic PC with TTL video. I get a decent picture, but the colors are totally wrong. The intensity input of the monitor was put in GND, as the Alphatronic does not have an intensity output.

Using an IBM XT compatible with CGA output gives no picture at all.

Does anybody have an idea whats wrong here? Can anybody give an advice if the jumpers of the PL103 link block are set correctly for TTL operation? Whats the purpose of the analogue input board?

Best regards
Stephan
It looks like you have the Microvitec variant which was intended for use with their Apple II video card. The colour palette you have looks very similar to the colours that can produce. See this post: https://stardot.org.uk/forums/viewtopic.php?p=412755

For CGA you need to program a different PROM to go on the interface board, which would map the CGA RGB+intensity coding to RGB values. The service manual also mentions that the blue channel resistors are different for the CGA version (100 Ohm vs 220 Ohm), so some tweaking may be needed there if you want 100% accuracy.

Otherwise if you want to keep your monitor original, you can make a clone of the PROM board (it's electrically very simple) and make your own PROM to do the colour mapping. The Python script I posted in that Stardot thread will probably be useful if you wanted to do that.

I'm looking for information on the Apple II side of this setup, as I have one of the cards but none of the documentation.
 
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