Toshiba C870 Dead

[sandrabrnelic]

Hi !

I have C870 laptop that is completly dead. PS is OK, but when i press power button absolutely nothing happens (no noise/no lights) Mother board is PLF/PLR/CSF/CSR UMA MB REV 2.1 and the problem is that i can't find schematic. I found it on elvikom.pl forum but i don't have points to be able to download it. Please if anyone has schematic, i would be very happy to see it

[sandrabrnelic]

Re: Toshiba C870 Dead

update: found Si7326DN mosfet burned, will try to change it when i recieve replacement, but i still need schematic

[dommu]

Re: Toshiba C870 Dead

hi. I have the same MB and the same problem. Did you fix it? i found a fdmc 8884 mosfet shorted, but i can't find the one that you changed. Where is it? Thanks in advance.

[Miky1987]

Re: Toshiba C870 Dead

Hi! I have the board from Toshiba to.. It's C870-1EX, MOBO: PLF/PLR/CSF/CSR DSC MB. (As I have researched it's the same platform that's from Toshiba C850). So Board starts, but there is no Video (there is no external display either). A computer is taking steady 0.9 Amps when ON. The computer was working OK, in the evening they shut it off like always, but the next power on there was no picture on the screen. Measured all voltages present +VDDC_VGA, 1,5VS_VGA, +3VS_VGA,+DPEF_VDD18, VCCORE present, VCCRAM 1,5V, Signals RSMRST# is 3V3, PM_PWRBTN# (DNBSWON) from EC goes LOW on Switch button press, and then HIGH again after release. SUSCLK# is 1,6V (PWM 50 % Duty). LID_SW is 3.3V. I'm still waiting for a programmer to check bios, but if I understand correctly if RSMRST# is present than the bios should be fine? I will try to keep you informed if there is any progress.

[piernov]

Re: Toshiba C870 Dead

RSMRST# is handled by the EC. Usually if RSMRST# is present it means EC BIOS is ok. But EC BIOS is not the same as PCH (main) BIOS.
Your issue could indeed be related to the main BIOS not finishing POST, and flashing it may help.
This could also be a dead GPU or another issue. Make sure it not a no backlight issue, and make sure the LCD and LCD cable are ok. Try to see if the OS boots (any sound, HDD reading something, etc…).

[Miky1987]

Re: Toshiba C870 Dead

Thanks for quick reply, I tried to listen to HDD, this motherboard has no data bus LED, and I think that something is moving inside. But now after a few powerups, there was a noise from speakers, and now the mobo doesn't turn ON anymore. This is the second time that happened. Now is trying turning ON and OFF every 1 second, and drawing about .3 Amps. That started to happen when I removed CMOS battery(i think it has something to do with auto power ON when removing the CMOS battery). Before it just briefly took 0.3 A on PWR_BTN press and then nothing.. 3 and 5 VLDO and 3V, 5V rail present. On the oscilloscope screen, the yellow line is RSMRST# and the blue is PM_PWRBTN. Strangely enough that PWRBTN goes LOW after RSMRST# IS PULLED LOW..