Lenovo Yoga Slim 7 Pro-X 14IAH7 (NM-E301) - No external display through HDMI port

Hello

I have a Lenovo Yoga Slim 7 Pro-X 14IAH7 laptop that is not displaying through external HDMI port. The port looks good and i have tested with HDMI port tester, the filters/0 ohm resistors are all good and retimer IC is Parade PS8409A. From visual inspection there is no damage around the area. All drivers are up to date.




Thank you for your help.

Hello!

Set your meter to the diode test mode and measure the voltage drops to ground on points A, B, C, ..., R.

Yes no problem.

A = .511
B = .511
C = .511
D = .511
E = .511
F = .511
G = .511
H = .511
I = .605
J = .605
K = .423
L = .465
M = .423
N = .465
O = .425
P = .465
Q = .420
R = .462

Also there is no external display through HDMI when using a Linux Live distro or when main internal display cable is disconnected.

Replace the chip U68.

I found another Parade PS8409A from a scrap Dell board (CYBORG-H 19844-1).

I replaced the chip but still no display through HDMI.

Measure the voltages to ground on pins 1, 4, 6, 11, 15, 35, 43 of chip U68.

Voltage measurements for U68

1 = 3.3V
4 = 3.3V
6 = 1.2V
11 = 1.2V
15 = 1.2V
35 = 3.2V
43 = 1.2V

Measure the following voltages to ground:
- On pins 7, 8 of chip U68 with the external HDMI monitor connected.
- On pin 18 of HDMI port with the external HDMI monitor connected.
- On pins 21, 40 of chip U68 with and without external HDMI monitor connected.

With external monitor connected:
U68
7 = 4.8V
8 = 4.8V

Pin 18 of HDMI port with external monitor connected:
HDMI Port
18 = 5V

With external monitor connected:
U68
21 = 22mV
40 = 0V
Without external monitor connected:
U68
21 = 0V
40 = 0V

Do you have any other ideas?

The part of the board in question is very thin/flexible, and the solder was very low melt when working on the board. Is it possible the board has flexed/bent and some solder joints in the area may have cracked or become disconnected?

It does display to external monitor through USB-C Thunderbolt ports, with adapter and same HDMI cable. Just not at all directly out of the HDMI port.

Set your multimeter to the diode test mode and measure the voltage drops to ground on pins 1, 3, 4, 6, 7, 9, 10, 12, 15, 16, 18, 19 of HDMI port.
To access the pins use an HDMI cable with a cut end, or even better an HDMI test board:

1 = .547
3 = .548
4 = .548
6 = .548
7 = .547
9 = .547
10 = .547
12 = .547
15 = .642
16 = .643
18 = .143
19 = .688

I used one of these for the measurements.