Author Topic: Turbo Express has sound but no Video  (Read 116 times)

faro

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Turbo Express has sound but no Video
« on: April 13, 2022, 02:58:36 PM »
I am hoping someone here can help me figure this issue as I am having problems with my Turbo Express Video.

When I insert a game and turn it on I get sound and not video, if I shine a flash light to the screen I can see the game. I opened the unit up and can see that the Caps have been changed, could it be that the new caps are defective and I have to try and replace the CC501 cap (I am in Ontario, Canada and its a pain to try and source caps locally here anymore). If anyone have experience a similar issue and have resolve it, please let me know what worked for you. Thanks in advance for any help.

Keith Courage

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Re: Turbo Express has sound but no Video
« Reply #1 on: April 14, 2022, 12:20:50 AM »
I doubt the caps are defective but you should double check that all the caps have be changed without lifting up pads and that all values are correct. It's most likely one of 4 possible things.

1st, bad traces to one or more of the capacitors caused by old capacitor leakage/damage.
2nd, Shorted out via hole caused by old capacitor leakage/damage.
3rd, a bad transistor
4th, faulty transformer in which case the only option is to install a aftermarket screen.

There is also the minimal chance that the screen itself is bad but I've only come across that twice in the past 13 years of working on these things. So very unlikely.
« Last Edit: April 14, 2022, 12:23:33 AM by Keith Courage »

faro

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Re: Turbo Express has sound but no Video
« Reply #2 on: April 14, 2022, 11:39:09 AM »
Thank you for responding Keith Courage.

When I get a chance I will have to explore the options you laid out below as I would like to fix the unit and actual play it (It was working originally but the unit has been sitting for a number of years now).

MasterofBiscuits

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Re: Turbo Express has sound but no Video
« Reply #3 on: April 14, 2022, 03:23:58 PM »
Do you have any pictures of the mainboard? It's a faulty backlight, but that can be caused by a number of things as Keith said.

The good news is that you can see the game running, so you can always mod the screen for a modern LCD.

tawy

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Re: Turbo Express has sound but no Video
« Reply #4 on: April 15, 2022, 05:54:50 AM »
if you can see the screen with a flashlight, the backlight of the screen is dead or not powered.
you have to check the 5V on the red connector from the motherboard to the screen, if you can see the picture, the ribbon cable is fine (you have RGB hsync and vsync through these).
i think that the 5V from this ribbon is to feed the screen (dont need high amperage) and the 5V from the red connector is for the backlight.

i did try to connect the pcegt throught the video ffc connector to VGA and it works.
it is 15khz vga (cga ?), i had to connect the vga signal to an ossc to have a picture on a screen.

if you need a working screen, i can sell you one :)
but maybe a mod to a lcddrv will be a better solution, it's easier to a composite one and the image quality is flawless.