Lenovo g50-45 nm-a281 rev:1.0

[NConstantinou]

Hi all,

motherboard has all voltages but no display
near lcd connector there is an ic u7 which has pins 4,5 as inputs and i have 3.3v and on pin 3 en pin i have nothing. Is is not short.
I replaced ic 523am with ic 523pm but no change.


Am i on the right truck!

Thanks

[Sephir0th]

Re: Lenovo g50-45 nm-a281 rev:1.0

Without CapsLock responding on external keyboard there is no point to troubleshoot the display circuit. You did check that?

[NConstantinou]

Re: Lenovo g50-45 nm-a281 rev:1.0

thanks for your reply

do you suggest that i must have the keyboard connected in order to have
display!
pls explain.
i have used external usb keyboard BUT no light
thanks

[JaroTech]

Re: Lenovo g50-45 nm-a281 rev:1.0

Hi, do you have a picture on an external monitor?

[Sephir0th]

Re: Lenovo g50-45 nm-a281 rev:1.0

The external USB-Keyboard is the best indicator for proving that the device actually does the P.O.S.T.

In your case it does NOT so initialisation is not completed and you won't get picture for this reason.

So in my opinion you should work backwards from PLT_RST# and if everything is fine, troubleshoot the BIOS.

[NConstantinou]

Re: Lenovo g50-45 nm-a281 rev:1.0

Thanks Sephir0th for the reply

Troubleshooting all signals seems to work ok.
i will try to flash Bios tomorrow to see what will happen But worries me U7 enable pin3 no voltage


thanks

[Sephir0th]

Re: Lenovo g50-45 nm-a281 rev:1.0

Like I told, no need to worry about this area as long as the board does not successfully complete the P.O.S.T.

[mcplslg123]

Re: Lenovo g50-45 nm-a281 rev:1.0

It is always important to understand the logic and sequence of signal/voltages before troubleshooting. When mb is not even posting, it definitely doesnt makes sense probing LCD circuit as @sephirtOth has mentioned.

[NConstantinou]

Re: Lenovo g50-45 nm-a281 rev:1.0

If I tested all 13 points (power sequence from 1-13) point 13 is pls_rst# and all measurements look ok. There was a block diagram on the schematic for power sequence.

What is the next step I should take!

Thanks

[mcplslg123]

Re: Lenovo g50-45 nm-a281 rev:1.0

Dramrst# is not pulled low??

[NConstantinou]

Re: Lenovo g50-45 nm-a281 rev:1.0

Dear mcplslg123

i do not have DRAMRST# but i do have MEM_MA_RST# on pin30 of ddr3 which is 0v

[mcplslg123]

Re: Lenovo g50-45 nm-a281 rev:1.0

What we call DRAMRST# on intel platform is called MEM_MA_RST# on amd platform. This should not be zero volts and most of the times its APU fault.

[NConstantinou]

Re: Lenovo g50-45 nm-a281 rev:1.0

According to schematics MEM_MA_RST# is generated from G38 on CPU, then is link to dimm's on pin30.
if there is no voltage on DIMMA and DIMMB and the resistance is .325 in diode mode without ram. with ran on pin 30 of DIMM's is 0.
then what to do!

thanks

[mcplslg123]

Re: Lenovo g50-45 nm-a281 rev:1.0

Already answered. There is nothing inbetwwen cpu and ram slot pin30. So it can be either bios and/or APU.