Dell Duo 1090 help

[merkin]

This tablet has a screen that rotates. Unfortunately the owner over-rotated the screen causing the lvds cable to twist and rip, and there is a good possibility some of the lvds wires in the cable shorted out.

I ordered a new lvds ribbon cable and installed it, but the screen still does not show a picture, not even the backlight is turning on. I can hear sound as Windows loads which means the tablet is booting. There is no other video outputs on this tablet (such as hdmi or vga), nor on the expansion port.

So the problem is one of three things:
1. The led panel, or
2. The lvds signals from the motherboard
3. Both #1 and #2 above

I did something very stupid and hooked up the Dell Duo led display panel to my personal laptop (Gateway NV55S) as a test for #1 above.
This fried the RTD2132S (eDP>LVDS convertor) on my NV55S. I placed an order for a new RTD2132S but shipment will take a few weeks. The NV55S works with the HDMI and VGA outputs, but not the LED panel output so I hope the RTD2132S is the only chip that got damaged.

So now where do I go from here? Should I connect the Dell Duo to the LED panel of my NV55S to test #2 above (and risk even more damage)?

Does anyone have schematics for the Dell Duo 1090?

I have a logic analyzer which could test the lvds i2c signals, but I do not have anything to test the differential lvds outputs from the Dell Duo to confirm they are working.

If anyone has any ideas I am listening.

[orientalsniper]

Re: Dell Duo 1090 help

Test the KBC too, I think I had one case where I got no video signal (external works) and it was supposedly the KBC's fault.

[atsio]

Re: Dell Duo 1090 help

Probably you supplied the Asus schematic for reference of the RTD2132S. From what I know the NV55S has the LA-6973P board.
You probably damaged the Dell led panel because the pinout of the its LVDS is completely different (you supplied 19v to 3.3v rail, connected the LCDVDD 3.3v to ground rail, etc).
Have a look at the pinout https://cdn.badcaps-static.com/pdfs/...7efa2f3bbf.pdf.
You probably caused and more damage than to the RTD2132s of the Gateway laptop, probably the 3.3v LCDVDD rail.

[merkin]

Re: Dell Duo 1090 help

I uploaded the wrong schematic...I attached the correct one.

The lvds 40-pin pinout on the t-con board is the same for both led panels

https://cdn.badcaps-static.com/pdfs/...7efa2f3bbf.pdf

I did not use the lcd cable from the Dell Duo 1090 when connecting the LTN101AT03 panel to the NV55S motherboard.

What I DID do was disconnect the 40-pin end of the lvds cable from the tcon board of the B156XW02 and then connected that 40-pin end of the lvds cable to the tcon board of the LTN101AT03 panel. The LTN101AT03 panel never turned on. So I determined the LTN101AT03 panel was probably damaged when the screen was over-rotated causing the lvds cable to rip/shear, and the signals/wires to short out.

But next I connected the B156XW02 panel back up and now it would not come on either.

So why would damage occur unless the faulty LTN101AT03 panel (as described in my original post) caused the damage to the NV55S motherboard?

Any suggestions for an easy way to test the lvds signals coming from the motherboard, so I can troubleshoot?

[atsio]

Re: Dell Duo 1090 help

Check the voltages on all pins of the lvds connector to determine what is functioning

[atsio]

Re: Dell Duo 1090 help

Offcourse I am talking for the signals that are not comming from RTD2132S. For those you have to check on the pads of the RTD2132S.
You have to check for 3.3v and 1.2v (pads 3, 13, 18, 12, 11, 27, 7), APU_INVT_PWM signal on pad 16 (start inverter), and DPO signals on pads 2, 1, 5, 6 (and probably compare them with the CRT signals).
I don't know if it is a two way communication with the EEROM to test and the MIIC signals.
For the rest of the signals you need to replace RTD2132S.

[merkin]

Re: Dell Duo 1090 help

Did very little testing but here is an update...
There is no voltage across C1154
There is correct voltage across C1153
There is also no voltage across R713

I'll next be focusing on the circuits from page 10 of the schematic.

Any suggestions I am listening.

Thanks in advance.

[merkin]

Re: Dell Duo 1090 help

I finally replaced RTD2132S...now have correct voltage on c1154, c1153, and r714.

But the panel is still not turning on.

I checked the U22 (AND Gate) and there is 3.3v on inputs A and B, but only 1.3v on the output Y.

The LCD cable is good...passed many continuity checks. All voltage checks are good EXCEPT DISPOFF# which is output Y on U22 AND Gate.

DISPOFF# is active low signal...
B156XW02_V6 manual says VLED_EN needs 2.5v-5.5v for HIGH level.

R730 is 111ohms when laptop is not powered on and is 1.5Mohms when laptop is powered on, but schematic says R730 is 10Kohm.

1. Which part is defective?

2. Should I be able to see a faint image on the screen if the lvds signals are working and LED backlight is off?