MSX1 RGB output board

Hi,

I did also a RGB mod for my Sony HB101P using a TMS-RGB.
The good thing about the HB101P is that the motherboard is already prepared for a SCART connector (although there is no from-factory HB101 with SCART AFAIK) so the mod is pretty simple.

The service manual for the Sony HB101P explains how to disassemble the unit to get access to the motherboard.

Once the motherboard is uninstalled you can solder a SCART connector and a pair of resistors R84 and R83 that make a voltage divider for pin 16 (GND <--> R84 <--> pin 16 <--> R83 <--> GND) which is the SCART Blanking Signal and should be between 1 and 3V for RGB.
I'm not sure I did the right/wyse calculation for R83 and R84, but I chose R83=33 Ohm and R84=82 Ohm, assuming there is a 75 Ohm to GND on the side of the monitor... Someone with a real electronic background should pop in and shed some light

Note that in order to solder the SCART connector and the resistors first you need to remove the solder that covers the soldering points (the motherboard probably was soldered using a wave soldering process).
Also, note that I did not solder at this point the pads where the video signals (R,G,B,S) are located on the SCART footprint, I soldered them in a later step when soldering also the signal wires.

This is how the SCART connector looks from the top of the motherboard.

Then you need to solder wires to the R (red signal, red wire), G (green signal, green wire), B (blue signal, blue wire) and S (sync signal, purple wire) pads on the TMS-RGB (the 5V and GND are not needed as they are already prepared on the motherboard SCART footprint). Those wires need to be routed up to the SCART connector.
Continue by soldering the TMS-RGB to the VDP (TMS9129NL) on the bottom side of the motherboard, just like explained in the TMS-RGB site.

Then solder the signal wires to the matching SCART pins.
This is the detail of where each wire/signal goes on the SCART footprint on the bottom side of the motherboard.

And that's the electrical part: all signals (both audio and video) are already prepared on the motherboard.

Then comes the mechanical part.

First you need to cut a bit of the thin metal bottom plate to make room for the SCART connector.

Then make a hole for the SCART connector on the internal metal plate that protects the rear connectors.

And make a matching hole for the SCART connector on the rear of the plastic case.
I used a rotary tool to make the holes and a file to finish them.

Once all three changes are done (bottom thin metal plate, internal metal plate and external plastic case) the case is ready for the motherboard with the SCART connector.
Ah, I remember now that I had to trim a bit a plastic pin on the motherboard and the plastic fins of the SCART connector to allow the motherboard to rest on its original place.

Then you can follow the reverse order of the disassembly to assemble all things again, resulting in this.

And finally, time for some Konami fun with RGB enhanced video.

Cheers.

Just fitted a TMS-RGB to my Toshiba HX-10 and am using a 9 pin mini DIN for the output. Works with a Megadrive Model 2 SCART lead and is a great picture. It also will work with a RAD 2X for connecting to HDMI.

Just got my RAD2X and connected it to my HX-10 and then to HDMI and the output is crystal clear. There is the usual left shift but it's stunning. A great combination of hardware.