u/TheDressPainter

Hey everyone,

I’m working on a Sony TV that won’t power on at all (no lights, no response).

Here’s what I’ve done so far:

• Verified ~120V AC at the power input (CN6101)
• Checked the fuse on the power supply board (good continuity)
• Tested standby voltage (STBY3.3V) → reads 0V
• Tested using chassis ground and GND pin directly
• Confirmed multimeter is working correctly

I replaced the power supply board with a known replacement (APS-435), but I’m getting the exact same result:

• 0V on STBY3.3V even with the board fully isolated (only AC connected)

I also checked:

• Different grounding points
• Multiple pins on CN6401
• BL_ON shows only a few millivolts (~40mV)

At this point I’m trying to figure out:

• Is it likely I received two bad PSUs?
• Or could something else (main board, etc.) be pulling standby down even when disconnected?

Any ideas or things I should test next would be appreciated. I feel like I must be missing something. I can provide more photos if needed.

Thanks!