REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix

[XLR-VIII]

Hey guys can someone help me with this....
I replaced all 18 capacitors on my TE. End result is no video....backlight works and I have sound! Anyone got any ideas?

I attached a link to a video of my TE

[Keith Courage]

Looks like something isn't getting the correct voltage. Make sure there are not any broken traces to any of the caps you installed.

[RetroWeirdo]

Insulation of that part shouldn't effect anything. I've never seen flickering like you described. Maybe you should post some pics of the graphics issues? Could be bad ram/or damaged trace related.

Also, in the past I've accidentally uncovered the part you speak of before and have even broken off a leg/contact point before. I've always just re-soldered the wire back to where it originally went without any ill effects. Then cover up with hot glue or epoxy. So hopefully neither of the two contact points for the coil have snapped off anywhere.

Thanks for the advice KC. I tried some additional trouble shooting (different caps, reflow on solder pads) with no change. I posted a couple private videos to YouTube showing the pulsing flicker issue, here are the links:

Video 1: wayback://youtu.be/MevovLPARy0
_{(Turbo Express recap screen flicker - Recapped my Turbo Express and now there is pulsing flicker, more noticeable with the contrast down low)}
Video 2: wayback://youtu.be/g9rXBf_rj4E
_{(Turbo Express recap screen flicker video 2)}

If you look carefully in the first video you can also notice that there is a temporary burn-in on the screen that carries over from whatever is displayed previously, so in the video you can see the Keith Courage title screen still faintly showing on the screen once the game starts.

I rechecked the traces as well and couldn't find any issues, though it seems like that could possibly be causing the issue, or maybe the ribbon cable from the hu-card reader to the main board? What do think from the videos?

Thanks

[Keith Courage]

I've seen something similar happen when the 1 10uf cap pads get ruined but not exactly the same. Also, are you by chance using a generic ac adapter? Does the same thing happen on batteries? I wonder if this is the sign of an actual bad screen.

The burn in on the screen is completely normal.

[XLR-VIII]

Looks like something isn't getting the correct voltage. Make sure there are not any broken traces to any of the caps you installed.

I'm getting 7.8v from an AC adapter.
When unit powers on it drops to 3.8v
Checked some the caps, most read about 3.5-3.7v
Measured on pin 3 of the display ribbon cable only get -2.5v

Anything else I should check and where does the 24v start ?

Thanks

[RetroWeirdo]

I've seen something similar happen when the 1 10uf cap pads get ruined but not exactly the same. Also, are you by chance using a generic ac adapter? Does the same thing happen on batteries? I wonder if this is the sign of an actual bad screen.

The burn in on the screen is completely normal.

I will recheck the 10uf again. No I first tried this unit reassembled on batteries and noticed the problem, since then I have been trouble shooting it partially disassembled with power from a 1st party NEC TE AC adapter. That would kinda suck if the screen has a legit problem, Though it might be nice to upgrade to a newer LCD.

[thesteve]

Looks like something isn't getting the correct voltage. Make sure there are not any broken traces to any of the caps you installed.

I'm getting 7.8v from an AC adapter.
When unit powers on it drops to 3.8v
Checked some the caps, most read about 3.5-3.7v
Measured on pin 3 of the display ribbon cable only get -2.5v

Anything else I should check and where does the 24v start ?

Thanks

if your supply is dropping below 6V it wont work