Dear all,

I am starting this thread to seek help in the repair of a faulty dehumidifier power & control board whose replacement I am unable to find.

At this point, I have successfully identified a wary inductor blown in the circuit and an 'open' component in the series. I have 1 immediate question:

Attached pic 1 you can see a black cylindrical component next to the NTC 5D-9. It is in series with AC Power Supply Terminal>Fuse>NTC>This_Component. I am unable to figure out what this is. It is within the marking of NTC. Can anyone help with what this component is? It is showing as "Open" with DMM.

I am really hoping these will be only replacements. My understanding is: desolder these, find replacements, and install them back. Power up the supply and see what next. Is this the right approach? [I have already tested other resistors, diodes, and caps and their impedance/bias voltage looks OK]

Thanks for taking the time to help me bring this dehumidifier back online! I will keep you'all posted

 

It's a 1.5A fuse, it's marked on the circuit board, so it needs replacing, there must be something that has caused it to blow , check the bridge rectifier, and Mosfet or power chip.

 

@Dodgydave Thank you very much, hero.

About debugging what caused this to blew:
I have (in the circuit) a few caps, a VAR, diodes (bridge rectifier is implemented with bare bone diodes), RL filter, which I have verified.

There is also a THX202 (Datasheet): no idea if this can be verified without plugging power in.
Also, an EE16P10M2 flyback transformer appears OK on a short test. [further recommendation for verifying it?]

Then starts the DC circuitry with 7805 voltage regulation IC.


I would appreciate any advice in debugging what could have caused the fuse to blow,

 

Sometimes fuses just blow. It's good form to figure out why if one can, but simply replacing the fuse is a valid approach. It might buy many hours of service. If it blows again, then you have a research project.

 

@Dodgydave Thank you very much, hero.

About debugging what caused this to blew:
I have (in the circuit) a few caps, a VAR, diodes (bridge rectifier is implemented with bare bone diodes), RL filter, which I have verified.

There is also a THX202 (Datasheet): no idea if this can be verified without plugging power in.
Also, an EE16P10M2 flyback transformer appears OK on a short test. [further recommendation for verifying it?]

Then starts the DC circuitry with 7805 voltage regulation IC.


I would appreciate any advice in debugging what could have caused the fuse to blow,

Its a switch-mode chip, you can check if the pins 3/7/8 are shorted , the 5V regulator is a TL431 Zener diode, this switches the optocoupler to tell the chip to lower the output.