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Help me fix my kitchen hood

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RiRaRi:
Hello. My 5 years old kitchen hood suddently stoped working, completly. These are two boards that were inside. I tested everything i could. On PS board i tested relays, caps, therimstor, fuse etc. Big e-cap measures 0.2 ESR and almost identical capitance as written on cap.
On other board i tested voltage regulator and other things i could but for that i can not guarantee that i tested everything as it should be tested.
Transformer when unpluged from everything measured 17.5V, but when plugged 3V and it heats very fast and it becomes very hot in shirt period of time.
Weird thing that i noticed: when everything is plugged and i plug half-way the PS PCB in the switch board kitchen hood and lights turns on and switches work as they should. When i plug it completly it stops working. To be precise, not half way but just a little bit so probably only some of the pins acctualy connects.
I cleaned all plugs very good and tested for continuity when plugged and they all have continuity. What to test? What could be a problem? At least if anyone can tell me which board to replace?

RiRaRi:
.

RiRaRi:
Back side of PCBs

Swake:
Any markings on that transformer?
As you measure 17.5VAC I guess its rated voltage will probably be something like 14V.

The fact it only measures 3V in circuit indicates it is likely overloaded. The quick overheating indicates this too.
You have to find what is consuming all that power.

Have you checked the small square device on the bottom? I think it is a bridge rectifier. But it is likely ok as you mention things are working when half plugged.
There are 2 other 3-pin devices, likely transistors to switch relays.

Do you have a lab power supply that you can use to power the LED board with?

Careful, there is a solder smudge on the word Warning.

u666sa:

--- Quote from: RiRaRi on September 21, 2023, 11:57:19 pm ---Weird thing that i noticed: when everything is plugged and i plug half-way the PS PCB in the switch board kitchen hood and lights turns on and switches work as they should. When i plug it completly it stops working. To be precise, not half way but just a little bit so probably only some of the pins acctualy connects.

--- End quote ---

It's not weird. It's how they break!

You will have switches on your kitchen vitishka. I don't know what kind of switches you have, I have slide switches, and basically what happens is this -- fat from cooking gets into those switches and you have condition when pressing half way or fiddling with the switch will make your hood turn on. It's finicky.

Either replace the offending switch, or try to clean it using flux off.

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