Nucool TEC Fridge PSU acting up

[coolin67]

Hi all. A while back one of the fans on my Haier Nucool c-rnu281vs was making noise, so I would unplug it at night to sleep. I have since replaced the fan, but turning the fridge on and off has created another problem.

It now will turn on for ~6 hours, then stop running and making a clicking noise from the PSU, maybe once per second. If unplugged for a day or so, it will again run for a few hours and then stop again, with the same issue. I was hoping to be able to repair the board, but don't really know where to start. I have taken pictures of the board and will include those in the post.

Let me know if any more information or pictures are needed.

Thanks in advance to any help.

Kevin

[stj]

Re: Nucool TEC Fridge PSU acting up

look at the bottom of the board,
one of the transistors bolted to a heatsink has soldering so bad that the center pin looks like it was never soldered at all!!!!

look real close at ALL the soldering.

[coolin67]

Re: Nucool TEC Fridge PSU acting up

Are you talking about the hole next to c7? I don't think that there is supposed to be a leg soldered there.

Or are you talking about the transistor near R35/R36, where sharpee lines are?

When you say check soldering, do you mean check to make sure pins are sticking out? Here are some more pictures, hopefully of better quality.

Thanks for the help!

[stj]

Re: Nucool TEC Fridge PSU acting up

i mean look for cracked solder.

[japlytic]

Re: Nucool TEC Fridge PSU acting up

I see a badly darkened polyester capacitor (used for current transfer) near two medium heatsinks.
From what I see, this power supply is a variant of an "old-school" design (TL494, two primary switchers in push-pull configuration, an artificial centre-tap formed with two 200/250V primary electrolytics, and a large polyester unit connected between the artifical centre-tap and the transformer) used with many low cost computer power supplies.

[coolin67]

Re: Nucool TEC Fridge PSU acting up

@ japlytic Are you referring to C16?
@stj thanks, just got a new soldering iron, will re solder all of the points

Thanks guys.

[japlytic]

Re: Nucool TEC Fridge PSU acting up

@ japlytic Are you referring to C16?

Yes, this is the capacitor I am talking about.

[coolin67]

Re: Nucool TEC Fridge PSU acting up

So you would replace that? Any idea what a good replacement would be? Not sure if the numbers are visible any longer.

[momaka]

Re: Nucool TEC Fridge PSU acting up

So you would replace that? Any idea what a good replacement would be? Not sure if the numbers are visible any longer.

It's probably a 1 uF, 400 V, 5% (if it has 105J written on it, it probably is). Check what yours says, though.

Here's a compatible one if it is 1 uF:
http://www.mouser.com/ProductDetail/...bpto1kSWtZk%3d
(part # ECW-FA2J105J)
I picked a 630V one, just in case. It will be a bit bigger, but that's good - can dissipate a bit more heat.

I also second stj's suggestion to check all the solder joints. If any of them look rough, cloudy, or appear to have a fracture "ring" around the component's leads, then re-solder them. A 40W iron and 60/40 solder with rosin flux core should work nicely for this.