Dear Forum, I'll need your contribution on this one... the screen doesn't power ON, also LED on control board is all OFF; so far I've been able to check PSU as OK, all the output are OK on osciloscope (12V - 5V - 3,3V). Also the 2,5V regulator (7507) on scaler board is OK, 12Mhz oscilator OK, TL431 (7444) output ref voltage is OK.
When pressing power button on control board, voltage goes from 3,3V to 0V on PIN 2 of CPU (7301) - from "K_PWR" bus. CPU as correct voltage on VCC... do I have a faulty CPU? or could you think of anything else to goes from?
Thanks to all.
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Re: Sony Vaio VGN-S4HP (MBX-129) cold start problems



Thanks for your reply. This board is a MBX-129. I've been searching for schematic but only found MBX-126 so far... anyone has this schem?...

Hi members, hope to get some help on my 1º post on this mobo; I could not find the schematic so far, another problem is the board doesn't have components designators on it!!!
So here's the resume of what's happening and what I've done so far:
- on power ON: we can hear HD starting but all shuts down after 1 second.
- tested usual perif, but all OK (mems, CPU, HD, TFT, ...)
- Measurements show presence of usual +5V, +3v, +1,5V on some step-down ICs, with laptop OFF (see picture)
- when trying to power ON, I can measure +1,8V for about 1s, but as said mobo shuts...

Re: New Members - please post your introductions here

hello forum, I've been a casual user for about a year now getting shared information from others members; now, as I think I can try to contribute here and also get more into technical I decided to register myself. Thanks for all members for sharing experience and also patience on explaining to others less technical how things work!