Sony XV-T550 demystified. Look here if you have one.

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Por NYYRIKKI

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21-02-2022, 14:43

evilborf wrote:

* the "short" is done directly with a wire... or is needed (i.e. is better) using a resistor of a few ohm? or what?
* the "short" must be an instant action ... and then the short circuit must be removed (with the machine powered on of course) ... or it can stay there ..

Direct wire is enough. It can stay there unless you need the port for something. Practically this causes same effect as plugging in joypad and pressing both up and down directions at the same time. How ever there ae only very few Joypads where this is mechanically possible.

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I've burned some Ic Sad ? Like in commodore 64/amiga when you kill the VIA/cia chip? What kind of check can i do?
Thanks a lot

There is no much that can cause such havoc. I believe only pin that can actually cause some damage is pin 5 that has +5v output. How ever as it is physically near pin 9 it is possible to short circuit it by accident.

First I would try if the mouse works on some other MSX just to rule out possible problem on the mouse it self. Then I would maybe plug in joystick to T550 while pushing the joystick to some direction. I think this should fool the mouse detection so that you get past the screen. Then I would try to plugin the mouse on the fly and see how it behaves = Does moving it cause anything to happen... Maybe I would measure between pin 9 and 5 and see if the +5v is really there... Or maybe I would try to run a cartridge game that I know without picture and try to listen from sounds if all the joystick directions and buttons work as they are supposed to and try to narrow the problem down from there... I can't say I have any master plan.

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PS: total different question ... This kind of Megacard https://www.msx.org/wiki/Fractal2000_SD_Mapper/Megaram_512kb it's ok for using the hack-update done by NYYRIKKI ?

No, AFAIK this has totally different firmware.

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