NMS 8255 composite/scart video repair

Por st1mpy

Paladin (900)

Imagen del st1mpy

14-01-2010, 11:55

I recently got a NMS 8255, and the output to the TV is not working well.

RF is OK.
SCART gets shaky image on top half of the screen (bottom is OK most of the time, but shakes sometimes.)
Composite Video out gets a lot of ghosting.

Is this a common problem that is easy to fix? I'm guessing I should look in circuits around video out. VDP must be OK as RF is showing proper image.

(Also, is there an English translation of the diy page of repair bas?)

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Por Repair-Bas

Paragon (1165)

Imagen del Repair-Bas

14-01-2010, 13:33

You can check the power supply if all different voltages are working.

sometimes the 1377p is not working.

Mostly I change the board for another one.

Por Eugeny_Brychkov

Paragon (1232)

Imagen del Eugeny_Brychkov

14-01-2010, 15:01

Composite signal ("video out", "AC" labeled connector) gets signal from the same source as RF modulator (from PAL encoder). Thus if RF picture is ok then composite should also be ok. Try another cable / check if there's a ground. You may also think about capacitor C323.

Shaky SCART ("AM" labeled connector) may be because of problems with /SYNC: there're IC302, Q314 and C301 involved.

Important to note that RF+Composite and SCART take /SYNC from different outpus (and different cirtuits) thus /SYNC issue can be troubleshooted separately in case VDP output signal is ok.

Which connector do you use for composite out?