Dell Inspiron N4050 missing BUFO_CPU_RST

[mcplslg123]

Modelell Inspiron N4050
MB: DV14_HR_MB 48.4iu15.011

Problem: Missing BUFO_CPU_RST

It came with no display(but switching ) condition. I noticed that there is no core voltage. Traced it to missing 15v run power(it was showing 4.5v). Replaced TPS 51125(pu4101). Got core voltages but still no display.

There is no corrosion or liquid damage. I'm getting voltage on coils. Checked power up sequence-Getting all sequence upto PLT_RST.

So the last power up sequence(BUFO_CPU_RST) is missing.

As per the attached schematic on page 5(U501) I'm getting 3.3v on pin 1 & 2, pin 3 is gnd, no voltage on pin4 and 3.3v on pin5. U501 is not populated on the mb though. 1.05VTT is present on PIn 6/7/8 of RN501.

I've flashed a known good bios dump and replaced PU4201/4101.

Can you please advise ????

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

Schematic here

[meritosari]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

Try change U501.

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

Try change U501.

Thanks for your response but i have already mentioned in post#1 that U501 is not populated in this mb.

[caspian]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

PLT_RST and BUFO_CPU_RST maybe shorted together on the mainboard for simplicity reasons.

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

[QUOTE=caspian;789060]PLT_RST and BUFO_CPU_RST maybe shorted together on the mainboard for simplicity reasons.[/QUOTE

Do you mean to jumper between plt rst and bufo cpu rst signal??? Else i have not understood you.

[caspian]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

yes, there may be something like a jump by manufacturer.
just maybe

[meritosari]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

Check R510

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

yes, there may be something like a jump by manufacturer.
just maybe

I tried that as well. No result

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

Check R510

R510 measures 1.5k and thats ok as per schematics. I have checked resistance of R509 also. They are all ok.

[smali]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

check c501 and also check with another CPU.
oh sorry c501 will be not present your board is not UMA i think.

[JaroTech]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

Hi, check if you have the signal on the pad R1807, the PLT_RST# signal (page 18) comes from the PCH.

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

Hi, check if you have the signal on the pad R1807, the PLT_RST# signal (page 18) comes from the PCH.

i have plt_rst signal and i have already mentioned that. Mine is Discrete graphics mb. CPU -i have changed too many and all are working on another mb. So its, mb problem only.

[piernov]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

What is the voltage on both sides of R510?

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

What is the voltage on both sides of R510?

3.25v on one side and 1.09v on the other side.

[meritosari]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

So I think both side have correct voltage/signal.

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

So I think both side have correct voltage/signal.

Yes

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

But still not getting any voltage on pin4 of U501. As per schematics, pin4 is bufo_cpu_rst

[JaroTech]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

The BUFO_CPU_RST # signal will only be available if you have the U501 chip, on your motherboard all components with the DY symbol are not populated around the U501 chip. The PLT_RST # signal is not buffered for the CPU, it will only pass through R510.

[mcplslg123]

Re: Dell Inspiron N4050 missing BUFO_CPU_RST

What next then???