PC engine GT SMD repair/replacement

[famiac]

Hi guys, new to the forum here, but i hope i can stay and contribute. Currently new to NEC world.

So i bought a PC engine GT, but the previous owner damaged the SMD components on the power circuit, so the console will not work with batteries, but it will work with the AC adapter plugged in.

It's a strange problem, i know. The previous owner said the components were resistors but i have yet to open up and check. Another issue is that the screen has some color glitches. I'll post a picture soon. I suspect that changing the capacitors might fix this.

Does anybody have access to the schematics? Or would anyone be willing to help me once i find the exact part numbers?

[BlueBMW]

thesteve is probably the main man to ask on unusual problems.

[famiac]

Hm ok. I have some pictures. Apparently this is the result of a botched ac adaptor port replacement. While the previous owner was scraping the gunk off, he accidentally damaged some of the SMD components around it.

I'm guessing that first i need to remove the gray gunk to see what's up.
Also, this thing is long overdue for a cap kit. I'll do that once i get battery power working.

here are some pictures if anybody has any info:





This is with the AC adapter plugged in

[Keith Courage]

The easy fix would be to bridge a wire to fix the problem. I can't remember which trace it is but use a multi-meter to find out which pin is Positive for the AC adapter port and bridge the corresponding from the battery positive lead to the AC adapter.

Also, from the look of the AC adapter port solder job there could just be a damaged trace in the area.

Scrape off more of the Gray stuff in the area I circled in red. You should be able to find the positive for the AC adapter+batteries there.

[famiac]

Thanks for the suggestion! I'll try it out. Is there a better way to get rid of the gray sludge than scraping? I don't want to risk damaging it any more than it already has been.

[Keith Courage]

not that I can think of. Just use a small flat head screwdriver to slightly scrape it off. Obviously you don't push very hard. Besides, there aren't any other components hidden under the area which I circled in your picture. Only the contacts / connections you need to get to are there.

[famiac]

alright. It's scraped off. The damaged components are L501 and L502. I can't see where a trace could be broken, but while i was scraping at it some piece of copper came off, probably from one of the inductors. Does anybody know the values on them?

[Keith Courage]

Unfortunately I had no clue what the values are. Is it me or does that center pin for the ac port appear to have a bad/cracked connection? re-flow some soler on it. also, were you able to find the positive pin for the ac adapter port and batterie terminals? they both should be in the same area there.

[famiac]

The brown connector is the battery socket input. I think the batteries aren't directly connected to the AC input port.

[Keith Courage]

The batteries are not normally connected to the AC port. I'm just saying it's a quick fix and I've never come across any damage from anyone fixing it this way before. Seen it done this way quite a bit.

First you should re-solder that center pin for the AC Jack. The connection looks cracked. That may be the problem right there. If that doesn't fix it then move on to this next part.

Attach a wire to the positive battery contact found here(circled blue)


Run other end of wire to the AC port positive found here(circled red)


Use your multimeter to make sure you have the positive for both. Meaning hook up your power supply and test the pins in red. Put in some batteries and test the pins in blue.

[famiac]

Right. I know how to do all of that, i was just concerned about damaging the board by doing this.

Thanks for the info

[famiac]

Alright! So i rewired the battery connector  to the ac adapter, as you suggested, and it works!

I then went on to give it a full treatment. Replaced all caps, cleaned pcb/buttons. Works really well now.

Couple more questions:

Does anybody know where i can find button pad replacements? The rubber pads on my gt are kind of worn out.

Also, is the stock display really this awful?
The colors around the text are awfully inaccurate.



Thanks!

[BlueBMW]

That's the stock screen alright.  In all its awesome glory

[esteban]

Alright! So i rewired the battery connector  to the ac adapter, as you suggested, and it works!

I then went on to give it a full treatment. Replaced all caps, cleaned pcb/buttons. Works really well now.

Couple more questions:

Does anybody know where i can find button pad replacements? The rubber pads on my gt are kind of worn out.

Also, is the stock display really this awful?
The colors around the text are awfully inaccurate.



Thanks!

Have you compared this to other handhelds of the era? This was a nice screen. You crazy.

[famiac]

Hah ok. I'll take your word for it. I'll probably replace the screen though.