newbie advice - please identify this component

[bobalob]

Hi All,

I'm trying to repair a router, if I do a continuity test on the power input all of the pins are bridged so I took a look to see what the problem is. I've seen a component which looks a bit worn out and which bridges the pos/neg power input tracks.

It looks like it's specifically oriented based on the picture on the PCB so I'm guessing it's a diode but don't really know.

I took a pic so you can see - if someone could identify it either way and maybe give an explanation as to why it bridges the power rails I would be extremely grateful.



Uploaded with ImageShack.us

Thanks in advance,

Dave.

 

[davenn]

yes its a diode board part D8 it also shows you the circuit orientation for it
see the pic to the left withthe the looped drawing and the A and K below it

if it bridges the power rails then is probably a reverse polarity protection diode
which is usually done like this....

you can see that in that configuration with the power connected correctly, the diode doesnt conduct and the circuit operates normally.
BUT, if you accidentally reverse the power polarity, then the diode will conduct with almost short circuit condition and that resulting hi current flow will blow the fuse.

Hopefully some where in the power supply of your unit there is also a fuse?

Dave

 

[Resqueline]

It's a diode allright. They're often placed like that to short out the power supply should it be applied with the wrong polarity, thereby protecting the costly router electronics.
It seems to be smaller than the types I'd expect to be used for that kind of duty though. It's been hot but are you able to identify the color of the bands?
Also, an overview shot of the power input area there might help us verify it's function. That's the best closeup I think I've seen on this site to date btw..
Edit: Dave beat me to it..

 

[davenn]

Edit: Dave beat me to it..

haha

Dave

 

[bobalob]

Thanks for all your help guys, i pulled the diode off the board and hoping it was only for reverse polarity protection i plugged it it!

It works!

 

[davenn]

Thanks for all your help guys, i pulled the diode off the board and hoping it was only for reverse polarity protection i plugged it it!

It works!

cool, so chances are the diode is probably cooked. A replacement rated at maybe ~ 2A would be an ok replacement

D