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Dell Optiplex 745 won't start

Сообщений 1 страница 10 из 10

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Got for repair Dell Optiplex 745 almost dead, only led on mobo lights.

SIO : SCH5504-NS - Datasheet seems not to be available on the net.

Voltages measured :
Fnt_panel ICH_PWRBTN : 0V instead of +3V to be released by SB
though: RSMRST =+3.2v, clock signal is ok and supply voltage =+3.3V_AUX
PWR_PS_ON (green wire)=+4.9V
+5VSB ok

Based on SCH5514-NS datasheet available, which seems to be same as SCH5504-NS,
slp_s3 (pin123)  and slp_s4 (pin124) measured +3.2V, when only PSU is plugged. It should be +0V, before pushing power button.

When I shunted green wire to gnd continiously, computer boots and displays.

Any help as where to dig further to fix Dell issue.
Wonder whether SB needs replacement.

Отредактировано mohkamtun (10.08.2015 17:09:52)

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mohkamtun написал(а):

When I shunted green wire to gnd continiously, computer boots and displays.

what the green wire ?
What's with the wire ?

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3

freeqwer написал(а):

+ 3.3V_AUX PWR_PS_ON (Green wire)

PSU Green wire is PWR_PS_ON pin=+ 3.3V_AUX

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4

mohkamtun написал(а):

PSU Green wire is PWR_PS_ON pin=+ 3.3V_AUX

and if you duplicate , then everything works ?

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freeqwer написал(а):

and if you duplicate, then everything works?

Sorry, I didn't catch what do you mean by "if you duplicate" ?

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mohkamtun написал(а):

Sorry, I didn't catch what do you mean by "if you duplicate" ?

I mean this :

mohkamtun написал(а):

When I shunted green wire to gnd continiously, computer boots and displays.

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freeqwer написал(а):

I mean this:

Ok, then to summarize, Computer works fine when PWR_PS_ON pin of PSU (green wire) is shunted to gnd (black wire), but when pushing power button, computer won't start and +3V _PWRBTN: is absent (found 0V).

1*- where to dig further to fix this issue ?
2*- should it not be ICH fail ?

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8

To look in the direction of Multicontroller (EC) or circuit switching . Without the schematic I can't say.
Need to know why there is no tension on the button .

Or this option (works if you are using a PS/2 keyboard) :
To turn on the computer with the keyboard

Forcibly to turn on the computer.
To enter the bios
Main menu bios item a :
- Power — APM Configuration:
- Power On by PS/2 Keyboard - select a value from the list

Depending on the BIOS menu might look like this :
- Power Management Setup
- Power On by Keyboard

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9

freeqwer написал(а):

To look in the direction of Multicontroller (EC) or circuit switching . Without the schematic I can't say.
Need to know why there is no tension on the button .

Or this option (works if you are using a PS/2 keyboard) :
To turn on the computer with the keyboard

Forcibly to turn on the computer.
To enter the bios
Main menu bios item a :
- Power — APM Configuration:
- Power On by PS/2 Keyboard - select a value from the list

Depending on the BIOS menu might look like this :
- Power Management Setup
- Power On by Keyboard

The Dell mobo under repair has no PS/2 port-
Of course I can shunt the PWR_PS_ON to gnd and enter bios using an USB kb, but  if I have good understood that won't help!

So I need a pci to ps/2 adapter to follow your suggestion, which seems to be difficult to find nowadays.

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Well, it means looking for why there is no voltage on the power button

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