Pioneer PN50951-22U dead

[howardc64]

Got this free 2+ year old TV. Dead. Standby Light on. Power on (button+remote) does nothing (no screen display, backlight, SPDIF light, or coil voltage on speaker output section of main) Likely dead main from FLIR image

• All voltages present on PSU output to main
• Main board has onboard 1v 1.5v 1.8v 3.3v 5v when plugged in
• FLIR shows hot spot in middle of SOC
• Pressing power on shows no FLIR image change so basically no activity on main SOC even though it has power.

I have background in modern chip design. This main board has NO DRAM chips! so DRAM must be inside SOC. This means the MediaTek 9020 SOC on this board is either

1. DRAM+Logic chip process which is unusual. DRAM+Logic processes are complex and thats why there are separate logic and DRAM chips.
2. Multiple chip die package. DRAM chip die and Logic die reside on the same SOC chip package. Chip package usually more complex to interconnect the multiple dies. Apple M1 and AMD high end CPUs use this kind of technology.

Both options are fairly advanced and surprised to find it on budget TVs. Perhaps there is a cheaper form of these techs.

Toshiba has the exact same main board (probably manufacturer and Pioneer just used them for low end 4K TV) Are cheaper and more availability. Anyone know if the boards are interchangeable? (I understand will likely have Toshiba TV firmware afterwards)

[howardc64]

Re: Pioneer PN50951-22U dead

Got 2 main board from TVPartsToday.com. First one DOA, 2nd one boot but keeps crashing/hanging in different places and can't run firetv menu long enough to do anything.

Since I have 2 dead board and 1 booting crash/hanging. Thermal signature enabled fixing one board Here is diag path for future (This is a circa 2021 Toshiba firetv main board)

• Boot but crashing board showed the proper boot sequence. When first plug in AC. 1v and 1.2v rail will come alive for few seconds and then turn off. The Standby LED will start with brighter red and then dim when these rails turn off. This provided a basic understanding of boot sequence. Only heat signature is a hot spot on the SOC.
  
• On original dead board. The 1.2v rail never shuts off.
  
• On first DOA replacement board. A power converter chip (MSH6103A U105, probably generates 1.2v rail) glows red in thermal camera. The other 2 boards do not. This chip shows clear sign of rework. Replaced this chip and TV works.

Anyway, summary is

• TVPartsToday's is just shipping boards they have. And even on reworked boards (the correct chip was replaced but either improper or chip damaged during soldering or bad donor chip) clearly no testing. Have read other posts on poor products from them. But they are usually the lowest cost (even with $16 shipping in US) for the hhigh failure rate more rare and expensive boards.
  
• Thermal camera diagnostics is awesome

If anyone knows where to get datasheet for MSH6103A (might be the high failure part on this board), maybe I can rescue more boards by checking if SOC turns off this rail.

[howardc64]

Re: Pioneer PN50951-22U dead

If anyone knows where to get datasheet for MSH6103A (might be the high failure part on this board), maybe I can rescue more boards by checking if SOC turns off this rail.

Got a pinout for MSH6103A from the HiSense 65H6510G schematic.



Pin1 is enable. In case of this Toshiba board, enable is controlled by CPU 3.3v (probably GPIO) On the failed board. Enable doens't turn off few seconds after plug-in AC on the original dead main so SOC boot code is not progressing into standby mode. So unfortunately can't continue fixing this board (can't see into SOC)