I can't find the original thread I started so here's another one...

I finally took the time to take apart the ceiling light and it seems the swtich works fine. I have the Modifry delay thing. When I directly connect the wire that I had to cut to install the mod, the ceiling light works when the doors open (but no delayed turn off).

I looked around at anything that looked out of the ordinary on the mod and I found that under this thing it was toasted brown.


I figured that that was the problem because everything else looked to be ok. I took out the piece (don't know exactly what it is). My guess is that it somehow got REALLY hot slightly burned the PC board thing and fried itself?

What do I do? How do I check if this indeed is the problem and not something else? Where can I find a replacement? The exact numbers are IRF540 F 8913.

 

www.digikey.com

Part number IRF540IR-ND

 

is that a direct replacement? The picture is just an example of what the thing looks like... its not the actual thing... the actual one says IRF540 F 8913

 

bump

 

It's a pretty common N-channel MOSFET from Harris... pretty darn beefy for the project at hand, but beefy won't hurt anything. MOSFETS have very low resistance (milliohms), so you need a lot of current to create a good amount of heat. PC boards take a lot of heat to burn, so that thing must have pumped a LOT of current through it at some point (probably a short).

 

Damn... so do you think there's other damage as well?

Where can I find a compatible piece? Again the number on it says IRF540 F 8913

 

IRF540 is the part #, all of the other stuff is merely production date codes and package types. The one you pictured is a TO-220 package (most common for the IRF540 since it's a power FET). The part # Scanman listed form Digi Key is an acceptable replacement, though they have a $25 min. order.

I would consider sending it back to Modifry, though, let him repair it and hopefully determine what went wrong.

 

that's a good idea

Mitch

 

ok... well I PMed Modifry and hopefully he's not too busy.

I want to find the cause of the problem cause if MacGyver is right about PC boards needing a lot of heat to burn... I don't want something like this happening again, maybe even causing a small fire.

Hopefully I can get an answer soon.

 

Do a Google search on "FR4" and see what the specs are (I'm assuming Bob is using FR4 for his projects as it's the most common material). It takes an enormous amount of heat to make it catch fire (you're not going to hit that point with a component failing), but still a surprising amount to make it burn (i.e., turn black). I would keep an eye on this board to make sure it's not going to do that again.