ThinkPad P50 no power on

[wzamoyski]

Hello,

I'm looking for pointers/ideas:
- Lenovo Thinkpad P50.
- motherboard: BP500, NM-A451, VER 1.0
- schematics & Boardview: https://www.badcaps.net/forum/troubl...ic#post3242496

- CPU: SR2FU (i7-6820HQ)
- GPU: N16P-Q1-A2 (Quadro M1000M)
- MEC1653-BA1

When I switch on power supply motherboard take maximum 0.070A (without battery), LED1 is on after few second drop to 0.032A (LED1 is off). Pressing power button - case is the same.


Voltage/resistance:

• PL1 - 0.506V / 38kΩ
• PL3 - 0.00V / 86.7kΩ
• PL4 - 5.131V / 6kΩ
• PL5 - 3.369V / 6kΩ and higher
• PL6 - 0.00V / 2.3 Ω
• PL7 - 0.00V / 2.3 Ω
• PL8 - 0,00V / 2.3 Ω
• PL9 - 0.00V / 4.0 Ω
• PL10 - 0.00V / 4.0 Ω
• PL11 - 0.00V / 12Ω
• PL14 - 0.00V / 64kΩ
• PL16 - 0.00V / 29.4Ω
• PL17 - 1.020V / 70Ω
• PL19 - 0.00V / 7.07 kΩ
• PL103 - 0.00V / 9.0 Ω
• PL107 - 0.00V / 8,5 Ω
• PL108 - 0.00V / 171 Ω
• PL109 - 0.00V / 388 Ω
• L6 - 0.005V / 0.685kΩ
• 8 l.on SPI - 2.578MΩ

I didn't find any corrosion's, mechanical damages, etc. I tried new BIOS, but not working. I think VCCCPUCORE, VCCGFXCORE_I and VCCSA (according to schematic).


Thank you for any advice.

[mon2]

Review the charger IC @ PU1.

Measure the voltage to ground for the following pins of interest:

VCC ; pin 28
ACDET ; pin 6
ACOK ; pin 5
ACP ; pin 2
ACN ; pin 1
REGN ; pin 24

[nivminkov]

Probably not the issue but what about the main power rail? Does is shows in every input for the regulators? (on the input capacitors)

[wzamoyski]

Measurement (power supply/ original adapter):

• VCC ; pin 28 - 19,80V / 19.93V
• ACDET ; pin 6 - 2.67V / 2.69V
• ACOK ; pin 5 - 3.272V / 3.272V
• ACP ; pin 2 - 20.39V / 20.52V
• ACN ; pin 1 - 20.39V / 20.52V
• REGN ; pin 24 - 6.002V / 6.002V

When I try measure voltage on pin 6 (ACDET) current strength dropped to 0.009A.

Probably not the issue but what about the main power rail? Does is shows in every input for the regulators? (on the input capacitors)

Main power rail is good. After PR2 I have 20.39V.

[nivminkov]

I think you should verify that there is input voltage for every buck input. Most likely it will 😭
I also think your EC chip is gone. This is also the problem in a laptop I'm trying to repair. Main voltage present and also 3.3V and 5V. No shorts anywhere. I saw sorin from YouTube trying to fix a problem like this and he couldn't do it. He Replaced the EC chip and reprogrammiled it but still no luck. I hope you'll fix yours. Maybe flashing the bios memory chip with external programmer may help, but I'm not sure.
Try to look for your EC chip in Google and check if someone really succeed to replaced it.

[mcplslg123]

What about PL13? Does it have 1.2V?

[wzamoyski]

What about PL13? Does it have 1.2V?

Resistance: PL13 - 92Ω, no voltage.

I also think your EC chip is gone. This is also the problem in a laptop I'm trying to repair. Main voltage present and also 3.3V and 5V. No shorts anywhere. I saw sorin from YouTube trying to fix a problem like this and he couldn't do it. He Replaced the EC chip and reprogrammiled it but still no luck. I hope you'll fix yours. Maybe flashing the bios memory chip with external programmer may help, but I'm not sure.

I flashed BIOS memory without any effects. Hmm... I think my job is done here - I don't have programmer to EC.

[mon2]

There are vendors who sell the EC pre-flashed for this target laptop brand. Check eBay and AliExpress.

[mcplslg123]

You've not even reached S4 stage as ram coil voltage is missing. So the failure is in initial stage only. PM_SLP_SX rails status?

[wzamoyski]

You've not even reached S4 stage as ram coil voltage is missing. So the failure is in initial stage only. PM_SLP_SX rails status?

I can't find PM_SLP_SX. But if You need:
TP987 - 3.369V
TP988 - 3.369V
TP989 - 3.359V
TP990 - 3.369V

[mcplslg123]

I mean PM_SLP_S5/S4 etc.

[wzamoyski]

I mean PM_SLP_S5/S4 etc.

According to schematic available are -PCH_SLP_S0, -PCH_SLP_S3, -PCH_SLP_S5 etc.

Laptop return to owner.