[SOLVED] BLACK SCREEN on some LCD TV's with RGB MSX

By m3fisto

Supporter (4)

m3fisto's picture

23-02-2021, 22:45

Hi All
anyone interrested in making your MSX working on some incompatible LCD TV ?
i own a YASHICA YC-64 and a PHILIPS VG8020, both are RGB SCART output with an "ECI-SF0002" marked encoder board
and i found an easy hack for making them work on a LCD TV that would normally not detect the MSX video.
you need only a single 180 ohms resistor.
if anyone interrested i could post some pictures
best regards

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By Manuel

Ascended (17511)

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24-02-2021, 00:31

Um, why would you post this without posting the full solution?

By sdsnatcher73

Paragon (1521)

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24-02-2021, 05:06

Of course people would be interested, and a little suspense before the reveal is okay Wink

I assume you have the French models of these computers because outside France these machines actually only had composite video. I only had a French YC-64 at some point but that actually gave a good image on my 4:3 (first generation) LCD TV but I know more modern 16:9 TVs cause more trouble. So if a small resistor can fix that, please share!

By gdx

Prophet (4043)

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24-02-2021, 09:59

I suppose he disconnects AV then connects the resistor between the 12V and the SCART pin 8 (SWTCH).

By m3fisto

Supporter (4)

m3fisto's picture

24-02-2021, 12:48

Hi
i would love to post pictures of my little hack but i don't know how to do it !
sorry i'm not really confortable the UI of the forum. i do not see any "upload picture" button.
anyway just as said gdx, i disconnected the 100 ohms resistor that provide the Y signal from the VDP to the commutation pin, and i tied this pin to the 5 volts pin with a 180 ohm resistor. the resistor dissipate 100 mW so a 1/4W resistor is enough
this hack provide the 1,5 volt signal required by the TV for detecting the RGB signal (my TV requires 1 to 3 volts).
best regards

By Pentarou

Champion (316)

Pentarou's picture

24-02-2021, 14:49

m3fisto wrote:

this hack provide the 1,5 volt signal required by the TV for detecting the RGB signal (my TV requires 1 to 3 volts).

Then it would be SCART pin 16 (Blanking) and NOT pin 8 as suggested by gdx.

By gdx

Prophet (4043)

gdx's picture

24-02-2021, 15:14

His method is good. Mine is probably too old for LCD/LED screens.
You can try both if the MSX screen is wide instead of 4/3. By cons I don't know what resistance exactly is needed.

By m3fisto

Supporter (4)

m3fisto's picture

24-02-2021, 21:01

Pentarou, i confirm that my hack concerns the pin 16 on scart
gdx, depends on the voltage you apply : i measured 66 ohms at the scart input (pin 16) of my LCD TV
(each video signal input should be internally terminated by a 75 ohms resistor inside the TV. that's standard.)
i need 1 to 3 volts for RGB detection
https://en.wikipedia.org/wiki/SCART
so i use the 5V supply i need a 180 ohm resistor, that gives 5 x 66/(180 + 66) = 1.34 V
if i choose 12V i will need a 470 ohm resistor, that gives 12 x 66/(470 + 66) = 1.47 V

i do not care of the aspect ratio because any modern TV allows me to stretch and crop the image

hope you will find that useful
best regards