Burned element on a turned off DE2 Board

Altera_Forum · ‎02-21-2009

Hello all

I have a Cyclone II DE2 board and I'm using a 9V / 2A power supply. I have been using this power supply for some time now and all was working fine. When I finished working I turned off the boards power with the SW18 power switch (but it was still plugged in to the power socket in the wall). After about 10 seconds +/- there was a power glitch (I heard a spark) and I saw smoke coming out of the circled part on the below screen:

http://img14.imageshack.us/img14/3294/alterade2.jpg

The glitch was on a turned off board! :confused:

Does anyone know what does this part do and is it replaceable? Also a probable reason for this cause?

There is only a sign "470" on top of it and (I think) L4 written on the board around this part. It still smells and I can't turn on the board.

Please help

Regards 4 all.

Altera_Forum · ‎02-21-2009

Hello

Highlighted element is a inductor in DC-DC converter. It's hard to damage such element and I think that smoke became from DC-DC regulator( on the right side of inductor) or other components like diodes.In case of inductor damage only failure mode is breaking the copper wire. Both elements are repleceable.

Regarding component description is it coil with inductance equal 47uH (in a case of DE2 board). Do you use DE2 or DE2-70?.

Probable reason of these damage? It's hard to say. Maybe the quality of component was poor.

Altera_Forum · ‎02-21-2009

Unfortunately, the damage may be larger than it seems at first look.

There's a DE-2 schematics with the DE-2 documents, the said part is L4 on page 20 (Rev. 2.0), it's the inductor of the 3.3V buck converter. It's very unlikely, that the inductor get burnt without other parts being defective before, particularly the SMPS chip U22 has a current limit. The inductor may get overheated at this current limit, but most likely not immediately burnt. So U22 can be expected to be damaged too. Finally, if U22 has a short, the 3.3V supply would be most likely driven to higher level. In this case, the board would be most likely done.

Also S18 is apparently damaged, otherwise the board couldn't be powered in off state. The wall adaptor may be defective as well.

L4 and U22 are parts available from many catalog distributors. L4 is s 47 uH/3A 1/2" square shielded inductor, U22 is a common National part. As a first try, I would connect a laboratory voltage supply and feed a low voltage (1 .. 3.5 V) at the input to check the state of the possibly affected components.