ACER SF315-52 working but no lid display.

[coltron]

Hi hope someone can help with this acer sf315-52.

HDMI is working fine, but replacement laptop screen (slim type) won't initialise

schematic link below

At the https://www.badcaps.net/forum/showth...light=SF315+52

Diagnostic so far:- (with known good screen connected)

volts on 5 pin U4501.

pin 5 has 3.2v
pin 1 has 2.6v
pin 4 has 2.6v

The screen cable bells out fine with good continuity
Sockets and connectors have been cleaned with contact spray.

When screen is disconnected ( screen end unplugged)

pins 1 and 4 have required 3.2v

I don't want to replace the cable if it won't solve the issue? maybe something else going on...

Any help/guidance appreciated

[mon2]

Re: ACER SF315-52 working but no lid display.

Remove all power. Attach the display. Meter in resistance mode.

Measure the resistance to ground of pin #1 on U4501.

Remove the display. Measure the same again.

Post each measurement.

[coltron]

Re: ACER SF315-52 working but no lid display.

Thanks for reply Mon 2

200ohm range readings :-

screen attached 95.5ohm (96 on second reading)
screen disconnected 94.6 (94.5 on second reading)

[mon2]

Re: ACER SF315-52 working but no lid display.

Is the display a known good and compatible to the logic board model?

There is a possibility that this load switch has a discharge circuit that is internal but to me, the resistance appears to be low.

Flux and remove capacitor C4502 and then check this resistance again. Leave the display disconnected when checking the resistance.

If the resistance does not increase, flux and remove the load switch at u4501.

[coltron]

Re: ACER SF315-52 working but no lid display.

Thanks I will remove the components mentioned and get back to you.

The slim screen original to the unit (which is cracked) will display on a test laptop.
The replacement screen is a standard 30 pin FHD similar to the one removed.

FYI - Pin 5 - 3vs reads 10ohm, but voltage is correctish at 3.2v ?

[mon2]

Re: ACER SF315-52 working but no lid display.

FYI - Pin 5 - 3vs reads 10ohm, but voltage is correctish at 3.2v ?

This resistance is way too low. Something is wrong here.

Check the resistance to ground at the producer of this rail @ U9101A - pin #8/9.

Same resistance? Then check the resistance to ground @ U9101A - pin6/7. Same or higher resistance?

U9101 may be defective. You can flux and remove this part to see if the resistance increases. If not, there is a shorted part on this rail. In the end, this rail should output a stable voltage.

[coltron]

Re: ACER SF315-52 working but no lid display.

Thanks for response. I will check this out

[coltron]

Re: ACER SF315-52 working but no lid display.

pin #8/9. = 9.7 ohm
pin6/7 = 1k ohm

Although resistance appears very very low, how is 3v being maintained assuming a short?

Thanks Mon2

[coltron]

Re: ACER SF315-52 working but no lid display.

Strangely U4501. pin 5 remains at 3.2v when enabled, could the low resistance on 3vs be due to this switch?

[coltron]

Re: ACER SF315-52 working but no lid display.

For my own curiosity and relative ease, I've taken off the load switch U4501. to check if pin 5 trace was effected and unfortunately 3vs trace to gnd is still 10ohm.

U4501 pin 1 trace now appears open circuit in diode mode.

The u4501 switch removed and measuring resistance across its pins 1 and pin 5 in the off state...shows 97ohm....

Time to remove u9101......

[coltron]

Re: ACER SF315-52 working but no lid display.

With u9101 removed, 3vs is still 10 ohm.

I'm not sure how to proceed to find the source fault.....power injection?

[coltron]

Re: ACER SF315-52 working but no lid display.

The u4501 5 pin load switch has 5244W written on the top, would be interesting to know if the 97ohm reading between pins 1 and 5 is indeed low for this switch?

[coltron]

Re: ACER SF315-52 working but no lid display.

according to schematic, G5244T11U is a 120m ohm high side distribution switch

can anyone advise what the resistance stated refers too and how it might relate to pins 1 and 5 measured resistance on the switch i removed?..

[coltron]

Re: ACER SF315-52 working but no lid display.

Any help appreciated with the above?

I just don't want to kill the PCH or something by injecting too much power?

[mon2]

Re: ACER SF315-52 working but no lid display.

3vs with 10 ohms to ground is of concern. Inject only 1 volt (not higher) onto this rail and check the current draw in your power supply used for the injection. Check who heats up.

[coltron]

Re: ACER SF315-52 working but no lid display.

Thanks mon2, will post results when injection completed.