What is this? From board on range hood

[timmy2]

This is from a gaggenau AH250-790 range hood. New part is $220

What is the blown part - can it be replaced? what with?

[hardwareguy]

It appears to be a power transformer.

Replacement should have a primary voltage (input) of 120V and a secondary (output) of 12V.

1.5VA....that's not much current at all!

1.5 volt-amps assuming perfect power factor is 1.5W so the secondary needs to be rated for at least 0.125A (125mA).

More VA/amps is advised if the circuit checks out...it looks like it was straining! I'd also make sure that the rest of the circuit is OK...a short elsewhere could have overheated the transformer. First suspects are any diodes or that round bridge rectifier. Check caps next.

[bluto]

Second on checking the caps. I fixed a power supply for a treadmill a while back for my folks. The thing was a POS. The filter cap dried out, burned up the secondary side on the transformer and blew up a diode in the rectifier cluster beyond recognition. The smell of burnt silicon permeated the whole house and really freaked my mom out until I could figure out that it was coming from the treadmill. All of this would have been avoided if the manufacturer had simply bothered putting a fuse on the thing.

Anyway, I was able to find a perfect match for the transformer on digikey. If you don't have their catalog, you can request one to assist in locating a match. I replaced the transformer, capacitor and the burnt diode (repairing some of the traces around it) and the thing still works fine to this day.

That board is roughly similar to what you have (runs just a few relays and a couple ICs). I would replace the transformer and caps before proceeding further. Check the diodes and any VRMs (does not look like there are any from the pics) for shorts before powering it up again. You may also want to put a fuse on the rig for testing so that you don't blow the new transformer while you are troubleshooting it.

And though it does not look like it, make sure that your hood does not have any crazy microcontrollers with embedded software like mine does:
http://www.badcaps.net/forum/showthread.php?t=8654

[bluto]

Can't sleep. Did some searching on that transformer. The brand name is 'pulse'
Here is one that should be really close to yours:
http://search.digikey.com/scripts/Dk...=567-1031-5-ND

And the line datasheet:
http://ww2.pulseeng.com/products/dat.../LT2007_08.pdf

Looks like a pretty small little bugger.

[timmy2]

Thanks for the update.

I think I trashed the board beyond repair - my fault.

[timmy2]

Bluto - The only thing I can really say - is NEVER buy a gaggenau appliance. Everything is over-engineered. The parts are expensive and the repairmen don't know how they work.

I will order the part you suggested. But I think I broke the board so I am not sure how to get around it.

Is there any miracle compound to fill in a blank spot in the board - kind of like the dentist might use - liquid plastic??

I am at wokr now - but will post a photo later.

[tj2]

There are products to fix broken circuit boards. Post pics of the damage; I'm sure that someone will know what to do.

[stj]

epoxy resin is good on busted pcb's - *NEVER* use cyanocrylate. (superglue, crazy glue etc.)

[timmy2]

OK- here are the pics. I admit it - I did it...
Can it be fixed?

[tj2]

If you know what the traces should be on the missing chunk, it looks fixable to me. I'd guess that the missing chunk only held a pad for one lead and part of a pad for another. There is also a broken trace, which can be fixed by soldering a wire jumper across the break after you epoxy the crack so that it doesn't propagate. Do you have the missing chunk to check the missing traces?

What is the white "fuzz" on the component side of the board? It looks worrying.

[Wizard]

Big deal. Blackened spots made PCB more friable and too easy to break. Get a suitable transformer, will be slightly different. Preferably one with wires leading out so you can mount it remotely.

You do have remaining pads to solder these wires there. The one trace, what you do is scrape the mask down to copper (lightly and completely.) Tin these with solder on one end and fashion a wire into L and tin wire. Solder the one end down then finish other end. Done.

Make sure there is NO SHORT on the output as this is main reason the transformer burned up.

Cheers, Wizard

[timmy2]

1-I think the white fuzz is from when the transformer blew.

2-I don't have the missing part -

3-Can you give me an idea of where I should most look for a short

[stj]

test any rectifier or diodes.

[timmy2]

I took a very close look at the board and decided that component close to wher the blown transformar was located looked "bad". Can somebody suggest a replacement part.

I really don't know anything about these components but am game to learn. I am talking about the brown item that looks like a big tick.

I am also posting some other shots for comment.

[timmy2]

Here are more shots for comment

[stj]

the black round thing with a + on top and 4 wires is worth checking.
what is all that white shit?
you need to get rid of that with a brush.

[timmy2]

I am not sure what the white stuff is, but I THINK it is from discharge from the blown transformer. I will clean off the board - for SURE!!

[bluto]

The brown disc that says 202m is a ceramic disc capacitor. The 202m means 2nF (nano farad), which isn't much. I would be most concerned with the gray cylinder that says 470uF on it (you also need to know the voltage, should be XXv next to the 470uf, but I can't see it in the picture). The gray cylinder is a electrolytic capacitor, the very type of component that caused the creation of this forum. I would also check the little black cylinder with the + on the top of it (it should have 4 legs coming out of it). That is the rectifier that takes AC from the transformer and converts it to DC. Although it is probably ok. Since the transformer was so wimpy, it likely blew before before anything else could be damaged. Right now my money is riding on the 470uF capacitor was the thing that went bad and caused the transformer to blow. Much like my treadmill story above. There is at least a good chance that I am right

[timmy2]

[QUOTE=bluto] I would also check the little black cylinder with the + on the top of it (it should have 4 legs coming out of it). That is the rectifier that takes AC from the transformer and converts it to DC. Although it is probably ok. Since the transformer was so wimpy, it likely blew before before anything else could be damaged. QUOTE]

I was unable to find a single unit (or small quantity) for sale. Can you suggest a replacement

[stj]

if the rectifier shorts it will take the transformer out.