Hello, the other day I began to follow tracks with the polimeter on the motherboard HB-F5 to know where some signals going, i remove some ic´s from its sockets to better view about the tracks,I have not done any modification important, only i change the eproms with MSX2+ update and when i tried works perfect, for the moment i didnt change the vdp, only the roms.
The other day I noticed something strange (had not yet changed roms) when i turned on the msx after a minute the screen turns off, and the msx is on. This happen as 2 times, today when i turn on the msx, nothing show in screen, seems that dont boot propertly, the msx power led is on but the CAP key and KANJI key dont turn on if i press it.
Seems like a video (composite signal) or power problem, i´m using a 220V-100V external transformer (100V-58W) with this japanese MSX (100V-26W), i used the tester to ckeck mainboard voltages and seems correct, now i´m checking if any resistor near video signals are bad.
Also remember when i tried a SCART Euro cable i didnt see any on screen, the i read some about The Japanese RGB 21 that this msx use, i hope not worn something using the SCART PAL, after that i built a RGB SCART 21 cable and neither works, seems like some video problem.
Could you help me with some guidelines?
Thanks a lot.
Regards.


Anyway: if situation is same with cooling plate back on then it's clear the +5V regulator is fried...
You're 2nd person to do that in a short while & it's a silly mistake - nothing personal, but people should learn to not f**k with their machines if they don't know what they're doing. 