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View Full Version : CGA to VGA Video converter to suit Amiga, C128, Microbee, Tandy CoCo3 & other retro systems



MbeeTech
2nd February 2015, 23:43
82659CGA to VGA Video Converter kit
for retro computer systems.

82660


Designed to enable the use of VGA monitors with older computers, the Microbee VGA
video converter allows for analogue or digital inputs.

The digital mode converts true CGA digital input (RGB + Intensity) and provides the proper
CGA color map. This is the mode that is used by the Microbee Premium, Premium Plus &
256TC models, along with regular IBM PCs and numerous other computers.
There is also a jumper to implement the 'Brown fix' for the Commodore C128's
80 column mode (normally in the CGA map there is a dark yellow which is supposed to be a
brown color on the C128's output - setting this jumper selects brown instead of dark yellow)

The analogue mode allows for use with other computers that have true analogue outputs,
such as the Commodore Amiga (the converter has been tested with the Amiga & works brilliantly!)
Normally it works with TTL level positive HSYNC & VSYNC as the timing signals but can also work
with composite sync. It has options to set the sync polarity for odd-ball video systems that differ
from positive sync (15Khz) via jumpers as well.

The circuit also cleans up the Sync signals (HSync & VSync) to provide true composite sync
(HSync XNOR'd with VSync) and rock steady display. The kit employs a pre-built video scaler board
along with an adapter board (which has to be assembled) that does the Digital CGA map conversion
& cleans up the Sync signals.
The Scaler board (GBS-8200) is also modified by us to cure a common problem (caused by poor
timing of the DRAM on the board) that causes random white dots on the output (snow).

Available as a complete kit with all parts, PCB and case, or as a short form kit with the adapter
pcb & parts for those who already have a GBS-8200 video scaler board.

The project has just been published as a 7 page construction article in Australias 'Silicon Chip'
magazine.

82661

The kit(s) can be purchased through our web store : Link <here> (http://www.microbeetechnology.com.au/vga_video_converter.htm)

Pictures of the unit working with: Amiga, Microbee Premium Plus, Tandy CoCo3, C=128

82670 82671 82672 82673

DerekP
3rd January 2016, 07:46
You should bold this bit:
The Scaler board (GBS-8200) is also modified by us to cure a common problem (caused by poor
timing of the DRAM on the board) that causes random white dots on the output (snow).

From what i understand, all those other eBay offerings from other places have not been 'fixed' like yours has :)

Technoid
16th May 2016, 23:01
Will you be restocking these kits or was it just a limited run?

Pgovotsos
17th May 2016, 03:42
The short form kit and short form with case are still available at their store at the below URL. The link in the OP doesn't work for me. Only the most expensive model is showing out of stock.

http://www.microbeetechnology.com.au/vga-video-converter.htm