Samsung Odyssey G9 OLED (S49CG934SUXEN) - No picture, no backlight, no LED

[platinum95]

Hi all,

I picked up an as-is monitor for repair, monitor has no visible damage but is also (mostly) unresponsive. When plugged in, the power LED remains off, monitor is not detected by PC over HDMI (or mini HDMI), and the buttons have no effect. The built-in USB hub is detected by a PC though, so there is at least some life in the unit.

I've popped the back case off, there are 3 major boards inside: Main display board (BN41-03181A), secondary/sub-main board (BN41-03182A), and T-CON board (BN96-56364B). This variant of the G9 display doesn't have an internal power supply like most G9s, and instead takes power from an external 20V 11A power brick.

I've checked the fuses on the v-supply input stages of each of the 3 boards, and they all seem fine.

When powered on, the secondary board has some faint coil whine, so I can tell it's getting power. DMM confirmed the 20V supply is delivered to it. This secondary board has a boost converter for the T-CON v-supply, and is DMM confirms it's outputting the 32V that is sent to the T-CON.

There's a very faint whine from the main board as well. The main SoC on the board gets hot when plugged in, so it's evidently also getting power. There's a "KEY-IN1" test point on this board that comes from the power switch on the secondary board. This is at 3.3v when powered on, and drops to 0v when the button is pressed. So the ON signal is at least making it to the main board.

Anyone have any thoughts on where to go from here? I have a scope so I can take some more detailed measurements if required. I should also have some hardware capable of reading the SPI flash if required, though I'll need some pointers on which one exactly needs to be read.
I'm also fine with replacing an entire board if I can find a suitable replacement, so if it's possible to work out which board the fault is on that may be enough.

Thanks!

[platinum95]

I've dumped the 2 16MB Winbond flash chips on the bottom of the main board. The left-hand one is erased and contains only 0xFF repeating. The rightmost contains what looks like valid data (found some ascii strings amongst general random binary).

Does anyone know what I should expect from these 2 chips? Or how I might verify if one/both has corrupted?

[platinum95]

Tried a replacement mainboard (BN41-03181A/BN94-18231Z), same issue persists. It's from a trusted seller, so unlikely (though not impossible) that the replacement has the same fault as the original.
I'll probe around some of the test points to see if I can narrow down the fault.

[platinum95]

I found a UART Tx pin on the main board that seems to be attached to the main SoC, and is sending out a system log. I've attached a dump of the startup sequence, but the main takeaway is that startup is stalling on a repeating log output of `SecDrvTcon_ReadPowerOnStatus: 00 00 00 00`.
This points towards the power management on the TCON board being at fault (or something in that general direction). I did find that the 'PMIC_FB33_ALERT' test point was high, though I'm not sure if this is alert asserts on high or low level. The 3.3v test point reads 3.3v.
I have a thermal scope that I used for checking for bad/shorted components, it's intended for wildlife use but is somewhat usable here if you stand far enough back to get into the minimum focus plane. (I do also have an iPhone FLIR attachment, but they've pulled the app version that runs on my old iPhone and have set the min iOS version beyond what I have.... thanks FLIR).
I've attached a picture taken from the scope with power applied, plus a reference picture of the board. I can't see any obvious bad components, but is it just me or is it suspicious that the 2 display processors not symmetrically hot? I wonder is there an internal fault in one of them which is triggering the overcurrent protection from the PMIC?

[lotas]

If the problem is in the panel, you can test it by installing feedback jumpers on the T-CON and disconnecting the cables going to the panel one by one (disconnect one cable, turn on the monitor and observe the monitor's behavior, then reconnect the first cable, disconnect the second and also check).

[platinum95]

Same issue, UART log hangs on a repeating `SecDrvTcon_ReadPowerOnStatus: 00 00 00 00`. I'll keep an eye out for a replacement T-CON board, and in the meantime continue trying to root-cause it in case it's an easily obtained component that needs replacing.

[platinum95]

Found a UART Tx test point for the 2 display processors on the T-CON board. They're both outputting the same thing, and boot-looping with the following output about once per second.
```
_____ BTA0BL1 Core[0] EMMC_____
ERROR : FW#1_CORE0 magickey error(0x0)
BL1 EMMC FW#2 core0,1
_________________ BTA0FW DQHD(VD) _________________
Keil 5060183, Build(Apr 23 2023 14:06:03)
Multi Inferface Master SPI Init
FW 1, CFG/MS 1
Boot GPIO CNT Over
system reset!
```

[tom66]

I suspect bad firmware for the T-con main processor based on that.

[platinum95]

That was my initial impression too, but it seems odd that both processors would have corrupted firmware in the exact same way since they each have a dedicated eMMC, unless there was an interrupted update procedure where both eMMCs were being flashed simultaneously. It does also fallback successfully to FW#2, so my theory here is that FW#1 is something like a factory calibration FW, and is wiped prior to shipping allowing the processor to fallback to the consumer firmware in slot 2 on boot.

[tom66]

It could be that only one is corrupted, but the communication between the processors is needed to proceed.

[platinum95]

Yeah that's true. Do you know where I could find the firmware image for the T-con? I'd need to source an eMMC flasher in the meantime as well.

[tom66]

Unfortunately not. Best bet is a second hand T-con if you can get hold of one. A complication for OLEDs is the T-con eMMC often stores calibration data; without this the panel image may be poor. In some cases, the calibration data is backed up to the main board, and the main board can synchronise it to the T-con through a procedure described in the service manual. In other cases, you have to extract calibration data somehow, which may be impossible, meaning you also need to replace the panel.. obviously uneconomical for many.

[platinum95]

I'll keep an eye out for a replacement T-CON, seems they're generally low availability, at least at non-ludicrous prices.
The service manual is another challenge to get, seems they're also like unobtanium.
I had a look for an authorised Samsung repair shop as well, since they'd have access to the diagnostic flows and service manuals. Seems the only one in my country closed last year 🙄

[platinum95]

Spoke too soon, got my hands on the service manual, but it's not very helpful unfortunately. The troubleshooting step is essentially "issue on T-Con?: Replace T-Con", no more detail than that.

[tom66]

Hopefully that means the T-con board synchronises from the main board then. But unfortunately I could not say for sure.