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Hello,

I'm trying to repair a SMS (first version) which only displays about half of the screen.

It's a PAL model MS POWER BASE/NTSC revision 837-6097.

The power supply is good, the cartridge connector is clean and I tried two genuine RGB cables.

At first I thought one of the two VRAM D4186C-15 chips was defective, so I desoldered both of them.
Of course when switching the SMS on, I got scrambled graphics but the problem remains.
So I resoldered both chips (but swapped their places, just to be sure they were not involved) and got the exact same image.

Which chip or component should I look at ?

Thanks for any help or advice.

IMG00303-20130812-1701.jpg (286.69 KB)

Display problem.

Quote

I'm trying to repair a SMS (first version) which only displays about half of the screen.

Do you get half the screen for all games tested? Or do some of them have other problems like corrupt graphics, badly colored graphics, etc?

Is there any garbage data or flicker past the half-screen point?

If you always get a half-screen display regardless of the game being played, the VDP chip is bad and you'll have to swap it out for another.

There's nothing else responsible for video than that and the VRAMs which could cause this problem.

Thanks Charles, that's a busted VDP.
I've tried two VRAM chips from another SMS, checked traces on the PCB and I got the same result with the integrated game or any other cartridge game.

And sorry to bump this old topic ;)

Author	Message
io Joined: 12 Aug 2013 Posts: 2	PAL SMS half display Posted: Mon Aug 12, 2013 3:54 pm
io Joined: 12 Aug 2013 Posts: 2	Hello, I'm trying to repair a SMS (first version) which only displays about half of the screen. It's a PAL model MS POWER BASE/NTSC revision 837-6097. The power supply is good, the cartridge connector is clean and I tried two genuine RGB cables. At first I thought one of the two VRAM D4186C-15 chips was defective, so I desoldered both of them. Of course when switching the SMS on, I got scrambled graphics but the problem remains. So I resoldered both chips (but swapped their places, just to be sure they were not involved) and got the exact same image. Which chip or component should I look at ? Thanks for any help or advice. IMG00303-20130812-1701.jpg (286.69 KB) Display problem.

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Posted: Sun Aug 25, 2013 7:24 pm
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Quote I'm trying to repair a SMS (first version) which only displays about half of the screen. Do you get half the screen for all games tested? Or do some of them have other problems like corrupt graphics, badly colored graphics, etc? Is there any garbage data or flicker past the half-screen point? If you always get a half-screen display regardless of the game being played, the VDP chip is bad and you'll have to swap it out for another. There's nothing else responsible for video than that and the VRAMs which could cause this problem.

io Joined: 12 Aug 2013 Posts: 2	Posted: Sun Oct 27, 2013 9:14 pm
io Joined: 12 Aug 2013 Posts: 2	Thanks Charles, that's a busted VDP. I've tried two VRAM chips from another SMS, checked traces on the PCB and I got the same result with the integrated game or any other cartridge game. And sorry to bump this old topic ;)

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