Saturday, July 18, 2009

TECH DOC: TurboExpress "No Video" Repair

TurboExpress/PC Engine GT
April 6, 2008
Written by: Nat Hall (hall.nat -at-

It's long been known that by replacing all the capacitors in the audio circuit on the Express PCB you are able to cure all sound issues, but video issues have been a bit of a grey area. What has been unknown (until now) is just which component is directly linked to the common video problem these units are beginning to have. Let's give a round of applause to my wacky cousin Sinisi, the real hero in all this, for donating a TurboExpress with bad video for me to butcher on the operating table.

The culprit turned out to be the smallest, most innocuous capacitor on the entire board. Real quick: the capacitor in question is in the power circuit, specifically, the line that supplies the mains to the LCD. This cap fails, dries out, bleeds, etc causing insufficient voltage supplied to run the LCD.

So let's get down to it.... I took photos documenting the entire process, but I'll only post the relevant ones here.

Circled in green is the audio circuit. We already know what these caps are for, so we ignored them for this procedure.
Circled in red is the culprit for the video issue. You can barely see it.

Since I didn't know where the problem was specifically, I removed the shield covering the CPU, VDC, etc. The caps circled in blue are the ones that are exposed by removing the shield. It is not necessary to replace these to fix the video. I included this pic so folks who might want to replace EVERYTHING can see just what's under the shield.

Circled in red is the replacement cap I installed in place of the bad one. The cap is a 4.7uF 35-volt electrolytic. This is THE culprit of the backlight-but-no-picture video issue. Replace it and your video works again.

There you have it. It's a simple fix, really, and luckily it's probably the most easily accessible cap on the entire board.

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