Power board in Ebac dehumidifier

[bbjunkie]

In the last week i've already repaired one of my faulty dehumidifiers, after gaining a little experience here on the forums.

Decided to give the other one a shot tonight, an old 1998 Ebac 11466TK-GB

I was shocked to find the PCB in the state it was when I opened the unit.

Just a warning to anyone with one of these units which miraculously is still working, be very careful!

I will repair this, but it will NEVER be left unattended ever again. The PCB sits at the very top of the machine, right below the wooden case. I can only thank my lucky stars this didn't catch fire.

Jim

[momaka]

Re: Power board in Ebac dehumidifier

That's some scary stuff.

Looks like the resistors are used to drop the mains voltage to a lower one that can be used by the logic IC. If that's the case, then this is one horrible horrible design. Repairing such a design will not solve anything. Stuff like this belongs in the trash. Seriously, how much cheaper is this than a small transformer or an SMPS?

Glad you caught it on time. If I were you, I still wouldn't use it, though.

[selldoor]

Re: Power board in Ebac dehumidifier

Wow! I'm on dehumidifiers too- just been getting an Ebac 6000 running.
I got it given as not working but it was actually only leaking - loose pipe on water pump. I will now have to take it apart again as I never got to look at the circuit board.
I also have another (not working for some time) and ran upstairs to see what make it is but it is an Amcor. It was going to be a next project but now
I feel I must get it opened up to check if it uses the same fire starting method!
I have another in pieces in the garage but it is a one without a compressor- has a disk which is heated then cooled - ive read how they work several times but cant really understand it. Lots of problem seem to arise but couldnt find much info on the internet on how to mend them.

I keep meaning to go to the reference library to see if there are any clues in home appliance servicing type books but too many more pressing projects.
Thanks for the heads up.

[tom66]

Re: Power board in Ebac dehumidifier

It's a capacitive or resistive voltage dropper. It looks rather poorly designed. The CR dropper isn't the greatest, but it is a cheap way of powering a microcontroller. The problem is, a triac requires a lot of current, so most likely those resistors dissipate a couple watts each...

An SMPS would be best for this design; you could take apart a 5V or 12V wall wart and fit it inside the case.

Not sure if a dehumidifier gets a lot of moisture; perhaps the board should have a conformal coating on the bottom?

[bbjunkie]

Re: Power board in Ebac dehumidifier

I also have a couple of Amcor's - they (touch wood) are still running though, no problems.

Selldoor - here in N.I. (I would assume it's the same in the rest of the UK) the local library is online, it's possible to register and search their inventroy. It's also possible to request or reserve books that way. It's very handy, I have a couple of books requested on SMPS and TV repair, from a library 70 miles away. When they arrive I will only have to drive to my local library 5 miles down the road

tom66 - excellent suggestion. Sounds much safer. I will probably go this route (after I repair the board and test the mechanical side of the dehumidifier, as it has been out of action for 8+ years)

The board itself probably isn't really subjected to that much moisture - not in the domestic environment they are designed to be used in anyway!

[lti]

Re: Power board in Ebac dehumidifier

I have seen some fans and heaters that use a custom controller chip and a triac, and they all used a zener diode to reduce the voltage and a small resistor to limit the current. This works well for the application. The last one I took apart used a 5.6V zener diode and a 330 ohm 1/2W resistor, and the resistor only ran at 40°C. The rectifier diode was connected after the zener diode, so the IC received 4.8V.