PC Engine GT Screen mod

[Vimtoman]

Ok I now have a working circuit/mod for the GT with no wiring to the Grafix chip.

This works directly from the flat cable lcd connection of the GT.

RGB + HSync to composite converter. 5V power.

Schematic below.



2.4" display link. You can ask for the 5V version.

http://www.good-display.com/products_detail/&productId=186.html

I have bread boarded the circuit and there is some noise on the picture.
The adjustable cap does allow you to tweek this out to a point.
I have not tried a fixed cap on the xtal or upping the RGB 0.1uf caps to reduce it.
This may help.

Schottky diode on the 5V is optional but advisable as Ive popped the fuse a couple of times connecting the flat cable incorrectly

I also used the original back light circuit board to wire the circuit to do the test circuit so you could do this.
Just remove all the components prior.

Overall the colours are good and the res on the 2.4" is 480 x 234 and preforms really well.
Not tried the 3.5"

There is another version which is a  AD725 IC and has a Luma trap circuit you can add which may preform better but I've not the time to do this.

Made some boards in the end. Tested and working.


SETUP

Allow the unit to warm up . Play system for 5 mins.
Fine adjust xtal pot to tweek out slight jitter on edges of red.

MODS

75r resistors on RGB input not needed.

For 7v - 12v lcd's tapping the switched DC input to power lcd points.


The 5v supply onto the ribbon cable needs a mod.
Removal of Q507 and shorting fixed 5V to ribbon connection is shown below.
Note wire does not connect to pads located either side of the wire. Only the central one.


If you need help or questions just PM me.

If you want PCB's with or without components PM me.

Gerbers are also ready so PM me with your email address if you want a copy.

I have 9 completed pcb's for sale and when they are gone thats all I'm going to do.
There will be some bare boards leftover so again PM me if you want some.

I will pass my gerbers onto Keith Courage who may make some for the future.

Enjoy.

[Keith Courage]

Ok I now have a working circuit/mod for the GT with no wiring to the Grafix chip.

This works directly from the flat cable lcd connection of the GT.

RGB + HSync to composite converter. 5V power.

This would be awesome!

[ltpitt]

Pure magic.

Keep us posted!

[ltpitt]

This also means that building a TV out could be way easier, right?

[Vimtoman]

Have made some boards shown working below.



The display I had purchased is not high enough res.
The 2.4" is OK.

Does anybody know of a 3.5" that is a high res 4:3 and capable of running at 5vDC?

[Vimtoman]

This also means that building a TV out could be way easier, right?

You could but you may have to sort out termination as driving two loads would double terminate the signal resulting in a dark image.

You could use the SVideo outputs which would give you a better picture on the TV.

It's doable though.

[Vimtoman]

Gerbers are also ready so PM me with your email address if you want a copy.

[fluxcore]

Great stuff. I'm waiting to find "the right" 3.5" screen to hack into my TE though.

[Vimtoman]

I'm waiting for one that's suppose to be 480 x 240.

[ltpitt]

Hi all and sorry for necroposting but the topic's still hot today...

I am one of the lucky owners of this lovely board and I've been using it a LOT.

I was just wondering if a Version 2 of the board was ever in plan or if you have found a screen of higher quality.

I'm basically just looking to improve the video quality on my PCE GT

[Vimtoman]

The 2.4" from Good display is 480 x 240. This matches the GT's display res.
I ordered a special with a 5v power rail.

They now have a lower res 3.5" thats sun readable. 240 x 320

http://www.good-display.com/products_detail/productId=212.html

I'm not making another version as most will go for the transistor based converter.

It's harder to mod but I think works better with the cheaper displays on ebay. Well  some of them