Microvitec Cub 653 Monitor (Type 1456 Li2)

[toshi]

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.

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.

Could anybody help?

Thanks a lot and best regards
Stephan

[AndyF]

pdf listing the variances on the 653 models (as there's a few) seems your's might be for the Apple range originally maybe. Not that it matters.

Microvitec.pdf

(551.08 KiB) Downloaded 46 times

Attaching an owners manual and a service manual as well

Microvitec_CubOM.pdf

(262.24 KiB) Downloaded 37 times

Microvitec-Service-Manual-Series-3-Colour-Display-Monitors-pdf.pdf

(1.24 MiB) Downloaded 40 times

Finally, what you probably wanted

[toshi]

Thanks a lot Andy!

I assume that the small BCB directly at the DIN plug makes the conversion to the Apple RGB colours? Now I have cut the the wires between the main board and the small adapter board and have hooked up my Amiga 500 directly to the main PCB of the monitor and I get a brilliant picture. Sadly, the picture is not stable but rolls horizontally. I have connected VSYNC, Red analogue, Green analogue, Blue analogue and Ground to the monitor.

According to the service manual, I have to adjust the field freq pot but this does not work. The picture goes either up or down, but I cannot find a stable setting.

May I ask for any recommendations?



Best regards
Stephan

[toshi]

By the way, I tried to hook to device (small PCB) up to CGA, but it does not work.....No picture at all.

[AndyF]

I can't (myself) help you with the specific details as its not really my area as such, sorry. Well its more a case of not being confident enough in anything I did say would be accurate that's all.

Others are quite likely to be along to help/assist though with a bit of luck.

[1024MAK]

“Sync.” on it’s own normally means composite sync., which is a combined vertical and horizontal sync.
If the vertical sync. signal is not detected, the picture will roll vertically.
If the horizontal sync. signal is not detected, the picture will roll horizontally.

So if the computer you are using does not produce a composite sync. signal, but does provide a separate vertical sync. signal and a separate horizontal sync. signal, you will need a sync. combiner circuit.

There is a sync. combiner circuit in this post

Mark

[toshi]

Thanks all for your posts!

Using Composite Sync, i get a crisp and clean 15kHz linear RGB picture with an Amiga 500 as video source.

Now I tried to hook up an "Alphatronic PC", a japanese made plain CP/M computer sold under "Royal" and "TA" brand names in the UK and Germany, which has a TTL video output. I used the small "converter board" between Alphatronic PC and the monitor mainboard, which makes the HSYNC/VSYNC to CSYNC conversion.

The video output is crisp as well, but the colours are wrong (e.g. not corresponding to the original colour table).

Has anybody a hint? On a Commodore 1084, the Alphatronic colours are correct, so the unit is working properly.

Could anybody please confirm the correct jumper settings on link block PL103 for TTL operation?

Best regards
Stephan

[IanS]

The video output is crisp as well, but the colours are wrong (e.g. not corresponding to the original colour table).

Looks like you are missing the red connection, re-check all your wiring. Try swapping Red with Blue or Green.

[toshi]

Looks like you are missing the red connection, re-check all your wiring. Try swapping Red with Blue or Green.

Thanks for the hint!
Unfortunately, all wiring is done correctly as far as I have checked. If I remove the connection to the RED signal, the intensity of the colours change. Swapping red with blue/green has only minor impact. still no yellow or red on the screen.

[tricky]

Is it RGB or component or CMYK - not that I know what I am talking about - just hoping to trigger a thought in someone else.

[1024MAK]

Simple way to test.

Command the computer to display a picture using only black and white [it has to be white, no other colour].

If the video signals are RGB, all three RGB channels should now have exactly the same signal. So on the Cub monitor side, disconnect all three RGB signals. Now connect the red and blue channels to the monitor to 0V/GND. Then in turn, one at a time, connect each of the R, G and B signals from the computer to the green channel going to the monitor. Be careful that nothing gets shorted out. If all three channels from the computer are the same (which they should be if it is an RGB output), each time you should see the same image (in green only) on the monitor for each channel from the computer.

If you get different results, either the output from the computer is not TTL RGB, or there is a fault with it.

Mark

[toshi]

Dear Mark!
Thanks a lot for your tips. First thing I have tested was another monitor again to verify that the signal source was working correctly (which was the case). Using your method, I clearly identified that the monitor was not showing the "red" signal correctly.
Now I have found the error: On link block PL103, I need to set R,G,B to "linear RGB" instead of "TTL". Obviously, the small adapter board with the ROM chip (does anybody know what is the purpose of it?) is responsible for converting TTL 5V to analogue RGB 0.7V ?
Hopefully, I am not killing my monitor with that setting, but it seems to work....

[Kazzie]

My CM8833 monitor has a separate board for the very job of converting TTL (5V) RGB values and 0.7V RGB, which was apparently an optional extra. My board uses two ICs (a 74ls368 and a 74ls05) along with a few transistors and passive components. I can't quite make out the markings on the IC in your photo.

[toshi]

I can't quite make out the markings on the IC in your photo.

Hi Kazzie!
Attached is a slightly better photo of the adaptor board's IC. Its a ROM. In addition, a 78L05 voltage regulator and a bunch of resistors, a transistor and diodes are on the board.

[Kazzie]

I can't quite make out the markings on the IC in your photo.

Hi Kazzie!
Attached is a slightly better photo of the adaptor board's IC. Its a ROM. In addition, a 78L05 voltage regulator and a bunch of resistors, a transistor and diodes are on the board.

That's clever. I'd guess it's using the ROM as a decoder, with four of the five address lines (R, G, B, and Intensity) selecting eight digital outputs, which are in turn driving three resistor ladders to generate analog values for the monitor circuitry.

If the ROM's become damaged over time, that explain why some colours seem to be incorrect when using it.

[toshi]

Thanks a lot! That makes sense!