Weird problem with modern kitchen hood

[RiRaRi]

Hello. My 5 years old kitchen hood suddenly stopped working, completely. There are two PCBs inside. Main one with transformer and relays. And second one with touch-sensitive buttons. On the power supply board i tested everything i could: capacitor, thermistor, relays, graetz connection etc. and it all measures good. Second one is full of small SMD components which i can not fully test. Connection between two PCBs is tested and fully working and connecting as it should.

Things that i noticed:

When i connect touch panel to power supply PCB, transformer starts to heat very much (can not be hold with hands), and voltage drops from 17.5V to 2.9V. Transformer is rated to 9V. Without any load and only connected to main PCB without touch panel/fan/lights measures 17.5V.

I did test with programmable DC PSU which i connected after graetz connection and when touch panel is disconected it measures no current but when i connect touch panel it reaches limit (draws more then 3A current). Here is video of my test: https://youtube.com/shorts/r7lAetzZ0N4

When i connect touch panel half-way and at angle LEDs starts to work, and at other angle fan is working but touch sensitive switches does not work.

When i power up switch PCB with my adjustable PSU it is short.

PS All connections and wire between touch panel and main panel are tested and they are good, so it is not bad plug.

Also, 4 of 6 (total) pins on switch panel are fully connected to each other.

Here are photos of both PCB

Thanks for your help.

[RiRaRi]

Power supply panel

[RiRaRi]

Can anyone help?

[blauerscharik]

With 3A shouldn't you be able to see what gets hot? With a thermal camera or some alcohol or touching?

[RiRaRi]

I dont have thermal camera. How to test with IPA?

[fzabkar]

U1 appears to be a linear regulator. If so, check the resistance between Ground and each of Vin and Vout.

Can you identify the markings on all your ICs?

[blauerscharik]

I dont have thermal camera. How to test with IPA?

If a component is shorted then you would be able to touch the board and find the general area where it is getting warm/hot. And then I would put a couple droplets of IPA in that area and see where it evaporates fastest and that would be your shorted component.