Acer xb272 t-con 27M14-C05 "SDLOCK" signal? - Page 1
Forum section: electronics / repair

author: StowAway
author_rank: Newbie
timestamp: October 25, 2024, 03:54:45 pm
content: Hello.Monitor Acer xb272, matrix AUO M270HTN02.0T-con 27M14-C05 CTRL BD: AUO-1H503, P303-19, S302-19, G201-19.Motherboard 715G7571-M3B-000-006N.White screen after start. Responds to buttons.It was opened before me. There was a typical burnt out Q308 on 27M14-C05 T-con. The transistor was replaced with AO3400. Was constant signal on the gate after startup, so the P303-19 controlling this MOSFET is under suspicion.Found an universal t-con (auo 55T32-C0F CTL BD), built on the same P303-19 chip. Resoldered P303-19, but half of the voltages did not start. Although all voltages are present on the original board.After careful consideration, it became clear that some voltages on these two boards are formed not in the same way. The idea came to me that there was firmware inside. Found SDA / SCL. Values ​​​​of all registers downloaded.Remotely bought a broken Asus VG278QR monitor with the same T-con board but a different matrix (M270HTN02.2) and everything else. With the help of a friend, the registers were read from the working t-con.Writing the working firmware was unsuccessful. I pulled down the WP pin, before, after, during - useless. The registers were saved only until the power was restarted. But I knew that the aliexpress are already releasing devices for adjusting VGH / VGL and they are definitely written to the same PWM controller. On the csdn.net I found a paid datasheet for a Chinese clone of this PWM - G2510S. From the datasheet it became clear that to write to non-volatile memory after all manipulations it is necessary to write the value 10h to the 00h register.After this the firmware was written successfully, all voltages started, the PWM status register reports powergood. But, unfortunately, the matrix remained white.VGH1 = 29.52, VGL1 = -12.16, AVDD = 13.17, 3.3/1.8/1.2 OK, VSS1 = -5.98, VSSQ1 = -10.13, VCOM_OFF = 5.05, LOCK = 0.12 (I don't know what it is).Since now it was possible to move all the voltages - I played with VGH / VGL / AVDD, no effect.On the gamma, as far as I understand, everything is fine: V1=12.21, V2=11.96, V3=10.57, V4=9.96, V5=9.35, V6=8.97, V7=8.73, V8=7.59, V9=6.75, V10=6.33, V11=5.46, V12=4.22, V13=3.97, V14=3.45, V15=2.73, V16=2.11, V17=0.56, V18=0.27Out of desperation, I ordered the same motherboard from xb271, the behavior did not change.Changed AUO-1H503, a scaler(?) that handles V-by-One communication. But just like in the beginning, HTPDN and LOCKN signals fell to the ground, which means that communication is started and the receiver understood the transceiver.There is no life on the AUO S302-19 level shifter, no control comes from the AUO-1H503. But on the cut off t-con (from that broken VG278 that eventually arrived by mail) level shifter is working. Next to 1H503 on the boards there are flash chips 25L4006E, swapped them, the behavior did not changed. There is a readout from the flash at startup.I did not find pinouts similar to AUO-1H503, so I measured everything around it on the cut off tcon board and on the original one. I found a difference. The 82 pin of the AUO-1H503 is pulled up to 3.3 volts through a 3 kOhm resistor. A 32 ohm resistor is connected to the same point, through which 3.3 is distributed across the board to the jumpers at the cables and the LOCK_X [cable number] testpoints, as well as to a separate SDLOCK1 testpoint. And after this resistor there is 0.12 volts on non working t-con. If I move the 32-ohm resistor, signals to the level shifter starts. There is no short circuit after the resistor (megaohms). When working, 1 mA goes there.I opened all the jumpers at the cables, the voltage on this resistor rose uniformly as the number of open jumpers increased, there was no abrupt change on some jumper.What is this SDLOCK signal? Maybe it should work like this and the problem is somewhere else? I am running out of options for what else to do.According to reports from colleagues, on the "sdlock" testpoint under normal operation is always 3.3.It is possible that AUO-1H503 is giving incorrect data on cof tabs because of broken firmware and they are dropping the signal to ground when they are not working. So I will be glad to have a known working firmware from M270HTN02.0. There was also an idea about incorrect voltage start timings recorded inside P303-19, but that's unlikely. But if someone has access to the same matrix, it would be cool to try everything.I am attaching a paid datasheet that is almost identical to P303-19, the contents of the registers of these PWM controllers on two different Tсons, dumps of the flash from both Tcons, the connection diagram for S302-21, the connection diagram for P302-11/P303-11, I hope this will help someone more than me.