Dell E6540 No RAM detected.

[Andreasbest]

Hello.
I bought a faulty E6540 recently that is in great cosmetic condition so i decided to give it a try.
For some reason the MB doesn't detect RAM properly, the Battery led blinks while the wifi and hdd activity are solid, according to Dell page *1 that means RAM detected but there was a "error".
What have i done so far:
1) I tried multiple RAM modules that work fine on other E6540 that i have here.
2) I flashed two bios. One from SMDFlea in this thread *2 and one from a E6540 that have here and work great, bios version A27.
3) I flushed CMOS (removed all batteries and charger, pressed power button for 20 secs)

No luck at all, the same behavior continues so any help is appreciated
Thank you in advance!


*1 https://www.dell.com/support/kbdoc/e...ps-and-tablets

*2 https://www.badcaps.net/forum/showpo...49&postcount=6


Schematics attached.

[Spider1211]

Re: Dell E6540 No RAM detected.

What is the blink/flash sequence? Is there any beeping sound?

[Andreasbest]

Re: Dell E6540 No RAM detected.

What is the blink/flash sequence? Is there any beeping sound?

Hello.
The blink sequence is Solid Blink Solid, check the attachment.
Without memory i get the usual sequence of "memory not detected" so it's reacting to memory installation.
Forgot to mention i have a exact same donor board

[Spider1211]

Re: Dell E6540 No RAM detected.

How many amps is the devices taking at standby and when turned on?

Check the following and report back:
1. RAM voltage (+1.35V_MEM)
2. +0.675V_DDR_VTT
3. DRAMRST#
4. DDR_XDP_WAN_SMBDAT
5. DDR_XDP_WAN_SMBCLK

[Andreasbest]

Re: Dell E6540 No RAM detected.

How many amps is the devices taking at standby and when turned on?

Check the following and report back:
1. RAM voltage (+1.35V_MEM)
2. +0.675V_DDR_VTT
3. DRAMRST#
4. DDR_XDP_WAN_SMBDAT
5. DDR_XDP_WAN_SMBCLK

I'm sorry but i don't understand. How many amperes where?
Also the measures you want to check are all voltages?

[Spider1211]

Re: Dell E6540 No RAM detected.

I'm sorry but i don't understand. How many amperes where?

Use your bench power supply to power your laptop. Set the voltage to around 19.4V and current limit to 2A. How many amps does the board take when you connect power to the board and how many amps does it take when you press power button (turning on laptop).

Also the measures you want to check are all voltages?

Not all, just the ones I mentioned above. Copy and paste the names in the schematic to find them.

[Andreasbest]

Re: Dell E6540 No RAM detected.

If i understand correctly in page 11 the +1.35V_MEM must be present @ PJP5 and PJP6?
Is that correct?

[Spider1211]

Re: Dell E6540 No RAM detected.

Yes, correct. You can also measure on the coil directly, that would be PL201. Also confirm is +3.3V_RUN is present.

[Andreasbest]

Re: Dell E6540 No RAM detected.

I see 3.3v on the power button but no +1.35V in PL201 neither in PJP5 and PJP6

[Spider1211]

Re: Dell E6540 No RAM detected.

Check if PL201 is not shorted to ground.

Measure continuity across PQ201 and PQ203. If shorted, replace faulty mosfet and try again.
If not, measure voltage on and report back:
pin 7, 8, 9, 10, 11, 13, 20

[Andreasbest]

Re: Dell E6540 No RAM detected.

Just to mention that QC6 is missing from my mb and from the donor board too.
Missing like never soldered even though the MB model is exactly the same with manual.

[Spider1211]

Re: Dell E6540 No RAM detected.

That's fine, most likely a No stuff part.

[Andreasbest]

Re: Dell E6540 No RAM detected.

Check if PL201 is not shorted to ground.

Measure continuity across PQ201 and PQ203. If shorted, replace faulty mosfet and try again.
If not, measure voltage on and report back:
pin 7, 8, 9, 10, 11, 13, 20

PL201 not shorted to ground.
PQ201 & PQ203 have only continuity on their common side, the rest pins are not shorted in any way.

pin 7, 8, 9, 10, 11, 13, 20 on which IC?

[Spider1211]

Re: Dell E6540 No RAM detected.

IC responsible for RAM voltage, PU200. Also check if 19V is present on drain (pin 5,6,7,8) of PQ201.

[Andreasbest]

Re: Dell E6540 No RAM detected.

IC responsible for RAM voltage, PU200. Also check if 19V is present on drain (pin 5,6,7,8) of PQ201.

PQ201 on drain has only 13.5v
That's a clue?

[Spider1211]

Re: Dell E6540 No RAM detected.

Not necessarily, measure the voltage on the pins and report back.

[Andreasbest]

Re: Dell E6540 No RAM detected.

7 0v
8 0v
9 12v
10 0v
11 0v
13 5v
20 0v

[Spider1211]

Re: Dell E6540 No RAM detected.

Check pin12 also. Also measure voltage on PL102. Just to be confirm, you are measuring the voltage with the laptop turned on (led blinking, etc) correct?

[Andreasbest]

Re: Dell E6540 No RAM detected.

Yes with laptop on (led blinking).
pin 12 5v
PL102 5v both pins

[Spider1211]

Re: Dell E6540 No RAM detected.

First check if pin11 of PU200 is not shorted to ground, then measure PR203 (with power disconnected from board). It should be around 5.1ohms.