No Power

[Shadow07]

I've got a 1.4 mobo that I purchased that's supposed to be in working condition. I have a known good 1.4 PSU. Clock cap was removed when I got it and there is no trace corrosion whatsoever and I've checked for continuity and correct voltages in all the correct places. I've replaced all the CPU capacitors. The motherboard looks pristine, however there is no response whatsoever to pressing the power button. I've even tried different power button boards. The PIC is getting the correct voltages to the correct pins when I press the buttons. What is left to check or repair?

Edited July 16, 2021 by Shadow07

[KaosEngineer]

The PowON signal out of the PIC processor to the PSU.  

And, the PowOK line from the PSU back to the PIC processor.

What voltage levels are they showing before you depress the power button, while it is depressed and after it is released?

 

 

[Shadow07]

Which pin does the PIC send the PowON signal from?

[Shadow07]

I can tell you that the voltage remains zero to the PowON line at the PSU before, during and after I press the power button as well as the PowOK line at the PSU. Whether or not the PIC is sending it at all I can’t tell you. There are several pins on the PIC that show 3.3V and drop to 0 when I press power and some that show zero and go up to 3.3 when I press power.

[SS_Dave]

Have you got 3.0 - 3.3 volt on the PowOk pin of the power connector?

 

Cheers

SS Dave

Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

[Shadow07]

7 hours ago, SS_Dave said:

Have you got 3.0 - 3.3 volt on the PowOk pin of the power connector?

 

Cheers

SS Dave

Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

Negative, it remains zero despite the power buttons being pressed.

[SS_Dave]

2 hours ago, Shadow07 said:

Negative, it remains zero despite the power buttons being pressed.

That's not good as the PowOk is a signal to the PSU from the main board and without it the PSU can not switch on any of the other outputs

When you press the power or eject button do you get any reading on the PowOn wire at the power connector? You should see 3.0 -3.3 volt.

 

Cheers

SS Dave

Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

[SS_Dave]

Can you upload some pics of the main board?

I use Postimages.org then add the links here.

 

Cheers

SS Dave

Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

[KaosEngineer]

19 hours ago, Shadow07 said:

Which pin does the PIC send the PowON signal from?

• Power Switch - PIC processor pin 18 - Input
  •    Logic level: 0 = switch pressed,  1 = switch not pressed
• Eject Switch - PIC processor pin 5 - Input
  • Logic level: 0 = switch pressed, 1 = switch not pressed
• PowON - PIC processor pin 16 - Output 
  •   Logic level:  0 = power off, 1 = power on
• PowOK - PIC processor pin 12 - Input
  •    Asserted when power supply is stable. 0 = power no good, 1 = power is good

 

[Hari125]

I'm not an expert or 100% sure, but that sounds like damaged or fried chip/chips (cpu/gpu/ram/microcontrollers), if it's not problem with the psu, caps or broken traces. It also could be faulty solder connections under the chip. Try heating the motherboard cpu or/and gpu with heat gun/hair dryier. [This is at your own risk]

Hope I am helpful