A1502 820-3476 no display on mini display port

[vincelx]

This board works fine with internal display, but nothing on the MDP.

The measures below are with an external display connected to MDP A

PPBUS_G3H =12.6V

TBT_A_HV_EN =0V
PP15V_TBT=0V
TBT_A_HPD =3.3V
PP3V3_S4_TBTAPWR =3.3V
PP3V3RHV_S4_TBTAPWR_F=3.3V

On U2800:
PP1V05_TBTRDV = 1.01V
PP1V05_TBT = 1.01V
P1V05TBT_SW = 0.95V
PP1V05_TBTCIO = 1.00V
PP3V3_S4_TBT = 3.3V
PP3V3_S4_TBT_F = 3.3V
PP3V3_TBTLC = 3.3V
PP3V3_TBTRDV = 3.3V

I checked all the above points also on a good board, same model, with the same external display on MDP A and blinking folder, and the values are the same.

I flashed the content of U2890 with the content of a good board, same model, and still no way to see something on the MDP.

Replacing U2800 would be the last move? It seems worthless. I have no more idea what could be checked now.

[mon2]

Each of these measurements look lower than usual:

(check against the good board)

TBT_A_HV_EN =0V
PP15V_TBT=0V

On U2800:
PP1V05_TBTRDV = 1.01V
PP1V05_TBT = 1.01V
P1V05TBT_SW = 0.95V
PP1V05_TBTCIO = 1.00V

[mon2]

Confirm each cap in the SNK0 AC Coupling and SNK1 AC Coupling group is present.