Sharp X1 Twin RGB?

Started by 3rdman01, October 28, 2020, 12:27:43 AM

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Hello all,

So I recently bought an X1 Twin and (from this board) learned that the RGB output from the back doesn't support the PC Engine portion which is composite only. So my question is how can I do an RGB mod to this?

I see that the video chip on the PCE portion is the HuC6270 which has RGB pins that I can pull from directly. I could then easily get Csync from the composite output and I'd get the RGB output I want but I don't see that anyone else has tried this.

Another thought I had was to (if possible) route the new RGB lines to use the same 6-Pin DIN connector for both the computer and the PCE. In my fever dream, I thought I thought I could split the Csync to H and V and land the lines from the PCE to the output of the computer to share the output. Another option I considered is to remove the H and V lines from the computers output and replace them with CSync from the composite and just have a simple scart output available to me at the RGB outlet for both computer and PCE...Thoughts?


I have one of these and have long considered such a modification.  How you proceed depends, of course on what your needs and wants define the project.

The PCE is a standard system as far as this project is concerned, so yeah, any RGB modification should work as fine here as on any other PCE. 

Re-using the existing connector somehow is certainly the right way to go, unless carving new holes in the system appeals to you.  That said, I've never seen a monitor (though I'm sure they exist) that wasn't happy getting C-sync on the H-sync line, leaving V-sync unconnected.  And, if you do combine h and v sync for your SCART idea, you'll have a very easy setup.

So yeah.  All things possible.  The choice is yours.  =)


Thank you! FYI I just got the machine in my hands...boy it needs some TLC. After dismantling and cleaning it, it looks ok and tonight I will try firing it up with the original PSU. In case it fails, my next thought was to use an ATX PSU to supply the +5v and +12V it needs.

Could you perhaps tell me what the pinout on the motherboard is for the PSU? There is only a single Molex connector with 4 wires...I suspect the red is the +5v and the Black is ground but I am unsure of the rest...Do you know perchance?

Thanks again!


Alas, I do not know the pinouts for the internal cabling.  You should be easily able to measure it with a multimeter (assuming it works) or track those pins to known points on the board (for example, Vcc on 5V chips).

Glad you got it, I hope it works!


It works! The entire system (sans the floppy) runs on +5v and Ground...The molex landing on the mainboard itself has 4 wires...
Purple=power on?

I probed around with a continuity meter and found that the purple line shorts to ground when the power switch is hit so I may try and land that line to the switch line of the ATX power supply to turn on. I think that the remaining white line is there for power check and to protect the computer from powering up on anything other than 5v???

EDIT: So yes, I landed the purple line onto the green "Power on" contact off the ATX power supply and it behaves exactly as I'd hoped. It turns the power on and off remotely from the system's switch!


I have another questions for you if you don't mind...

When I put the machine into "computer mode", it starts but only gets to a screen that says "Please turn on and off the power switch slowly" or something to that effect.

I don't have a keyboard which may be required to final boot. I also didn't connect the final white line of the motherboard so that too may be needed...Any insight? Thank you for your time!


I don't have a keyboard for mine either, but my X1 Twin powers up to a screen that requires a keyboard to select whether my software is on Tape, Floppy or whatever.  I believe that's the X1 standard. 

So I don't know what's up with yours.


Good news! Everything now works and behaves properly after applying the +5VSB line from the ATX power supply to the white line on the motherboard.

So...for the sake of others who may have an X1 Twin with a failed psu and they wish to swap out to an ATX power supply, you simply need to connect lines from the motherboard to the ATX wires following this breakdown...

Red=+5V (Red wire on the ATX Connector)
Black=Ground (Black)
White=+5VSB (Purple)
Purple=power on (Green)

The system turn on with the computers switch and everything runs perfectly. Thank you again for your time!


Forgive me for bumping up a very old thread.

My X1 Twin has a very strange issue that (has likely always existed but) I had not noticed before now as I mostly use it for its PC Engine. The oddity only appears if I load something with graphics (games of course) and ONLY if its set to Sync Mode "B".

If the game loads while set to "B", the graphics are corrupted...if however I were to load the game in "A" and then switch to "B" post load, everything is perfect! Sync Mode "A" is considerably less sharp than "B" so I'd like to solve this issue.

I've motivated myself to solve this problem so I am hoping for guidance here...

1. Could an owner of a working X1 Twin verify that my problem is unique to me?
2. My PSU solution (noted above) was done with a lot of guessing on my part...Could someone test their working power supply for the voltages at the mother board? I'm pretty sure I got it right but confirmation would be great.
3. Are there schematics for this particular board or perhaps the X1G which is very similar in design? I found a few X1 plans but they aren't specific to this model. Trying to decipher the circuits is next to impossible for a novice like me without schematics.

Thanks for looking!