Help! I have killed my PC Engine GT

[Keith Courage]

Transformer might have gone bad. I just worked on another one that had old leaky cap fluid under the transformer shorting things out. I had to remove the grounding plate over it so I could clean it up.

Maybe just your fuse went bad, if not then most likely the main power transistor B1182. See if the transistor is getting power and if it's sending it out again.

[MasterofBiscuits]

All is not lost! I replaced the fuse today and it is working again, minus display. I guess I hadn't checked it properly the first time around. I gave the board another really good clean and removed the transformer shield to clean under there but no dice. I do have some replacement Q500 transistors on the way so I will try replacing that and then give up.

So I will probably go ahead and replace the screen with a 3.5" I think. Are there any guides around for this?

[Keith Courage]

Here is how you get composite so you can use the new screen.

It requires a bunch of work to be done to the HU6260 chip.

Here are the screens for it. https://console5.com/store/universal-3-5-composite-video-lcd-module-320x240.html

Here is the wiring guide for the screen.  https://easyupload.io/j5ktf1

These things should really be backed up here so I'm not one of the only few with this stuff saved on his computer. Some of this used to be on Turbokons website but he has shut it down for now. Might come back later.

The composite work to the HU6260 chip can be a little confusing for some and risky since the pins can break somewhat easily if bent too much. I'll post a picture of the way I do it once I work on another one of these screen mods. I should be doing one within the next week.

[MasterofBiscuits]

Thanks - I was searching around yesterday and ordered a bunch of stuff already - I got the screen and mounts etc from Console5. I found this board on OSHPark so I ordered some:



They had the one with the same layout as you posted but this one has AV Out so I assume that's why it has an extra transistor. Thought I might as well get this one since that could be an interesting mod.

[Keith Courage]

Yes, those boards will work. I didn't realize there were some on oshpark now.

[MasterofBiscuits]

Quick sanity check - the 220 part on the board refers to a resistor, right? I have seen some boards with capacitors so I'm wondering whether that is 220uF or 220ohms?

[Keith Courage]

I've never used that board before but I feel pretty safe saying it's a Resistor.  It's extremely difficult finding any 220UF caps that are that small in size(0805 Ceramic).  What is weird is I don't see why there is a Resistor there though. 5V should be run to both Transistors. There is no need to have a resistor or capacitor in between them. The only reason may have to do with the type of transistor being used in the schematic. I always use a 8050 transistor.

[MasterofBiscuits]

Interesting, I'm none the wiser on how it works even looking at the schematic.

Is there a reason nobody uses RGB for these? Is it due to a lack of compatible screens? Would a screen with a VGA input accept RGB from the PCE GT?

[Keith Courage]

It's because the only place that sells suitable RGB screens is out in Japan and they will only sell to a Japanese location. No overseas sales according to their website. So you would have to go through some sort of third-party company to get one. Not to mention they are actually sold out on them right now due to supply issues.

If it were easier to get RGB screens, then that would definitely be a better option because one wouldn't have to go through this work of getting composite enabled for the system.

[MasterofBiscuits]

Oh so those would be the RGBDRV boards I've seen.

My wife is Japanese so we go there a lot, and she has family in Tokyo. Will see about getting some sent over when they are in stock again. We were due to be in Tokyo last month but the Covid situation put a stop to that 

[MasterofBiscuits]

Another update. While waiting for the parts for a 3.5" mod I decided to have a play around with LED modding the original screen. This is usually not too difficult to do and I had a DMG Gameboy backlight lying around. After fitting it and wiring it up I tried it in the damaged GT and there's no picture  So I tried it in one of my working machines and it worked fine.

The sound was a bit low for some reason so I decided to recap the machine again and it nice and loud now, but still no picture. I'm wondering if the 6260 is damaged? Or does the video circuit also depend on having a working backlight maybe?

[Keith Courage]

Price shining a light into the screen and see if you can see any video. You might also be able to see something if you look at it from an extreme angle off to the side or top. You should still be able to see something even when the backlight is out.

[MasterofBiscuits]

Price shining a light into the screen and see if you can see any video. You might also be able to see something if you look at it from an extreme angle off to the side or top. You should still be able to see something even when the backlight is out.

Tried it, nothing. The LED backlit screen worked on my other PCE. It looks like I have a video issue on that board too 

Hopefully running composite directly from the HUC6260 will work otherwise this board is done.

[Keith Courage]

Composite should still work. Every time I've had audio with no video, the Composite and RGB still work from the 6260 chip just fine. Well, S-video as well.

[MasterofBiscuits]

Damn, I wonder if my 6260 is fried.

Here is the LED mod running on one of my other GTs, it's not quite there yet, needs to be brighter and maybe some warmer LEDs, but I reckon battery life would be doubled or tripled.

Comparison with stock: