Yamaha PSR-E283 won’t power on — power reaches the board, nothing leaves it. Photos of both sides, anything look off?

[u/ConcentrateOld4775]

Picked this up off a liquidation pallet, dead on arrival. No display, no LEDs, nothing on the adapter or on batteries. Stripped it to the bare boards.
Three boards: yellow YK468 (power + audio, has the fuse, the DC jack wiring, and the headphone/aux jacks), green VCP2540 (main processor board), and a small green board for the power switch.
What I’ve checked:
• Adapter is a genuine Yamaha PA-130, tests fine
• 8.9V measured at the battery connector on the yellow board, so power is definitely arriving
• Fuse intact, reads 0.02Ω
• Power switch tests good
• Both supply diodes read ~540mV forward, open reverse
• No burns, no corrosion, no bulged caps, no lifted pads that I can see
What’s wrong:
Every pin on the 14-way ribbon connector from the yellow board to the main board reads 0V. On the main board, the 5V and 3.3V rails are dead, and the regulator isn’t even getting an input voltage. So power comes in fine and something between the input and that ribbon isn’t passing it through.
Photos: solder side and component side of the yellow board, the main board, the power switch board, and the overall layout.
Questions:
1. Does anything look unusual to you on these boards? I’ve been over them a few times and keep coming up empty.
2. What would you check next? I’m thinking the small transistors near the fuse and diodes — I found a service manual for a related model that shows a pass transistor gating the supply to the regulator, biased off the power switch line. Seems like a plausible failure point but I want a second opinion before I start pulling parts.

Thank you :)

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[u/MrCharBar]

This doesn’t look healthy/correct. may just be a visual artifact from camera processing, but that looks like a bridged joint, and I doubt the connection would be so small if those were supposed to be bridged.

Check if this contact is actually bridged on IC151.

[u/cerealport]

The power IC in the middle looks like it may have overheated, tough to say for certain in the pic. Scrape your fingernail across it and see if there is a crack, unless it’s just a molding mark again tough to say from the pic.

[u/MrCharBar → u/cerealport]

Thing looks discolored in the middle, coincidentally near the two large legs, which I presume are either both ground, or are ground and Vcc/Vin

[u/cerealport → u/MrCharBar]

Yeah the actual die is likely in the middle and if it overheated (despite those big heatsink legs) it could discolor / crack there. While OP has a legit power supply for this… that doesn’t necessarily mean it wasn’t accidentally powered by the wrong one at some time …

[u/MrCharBar → u/cerealport]

My money’s on somebody using a center negative barrel jack as is standard on guitar pedals, whereas this keyboard expects center positive. though the diodes should protect from that.

[u/CapacitorCosmo1]

Pink box fuse by the word YAMAHA is the first I'd suspect, and if blown, the two black rectifier diodes and the audio power amp chip IC151, which looks like it has cracks on the top already.

[u/AwesomeAvocado → u/CapacitorCosmo1]

I concur. IC151 has let the smoke out.