Author Topic: Magic Smoke Release  (Read 863 times)

0 Members and 1 Guest are viewing this topic.

Offline andersjm

  • Contributor
  • Posts: 15
Magic Smoke Release
« on: September 02, 2017, 09:32:37 am »
Hi forum,

Thought I'd share some pictures I took of the circuit board in a fluorescent light fixture that stopped working in our house. We got a new one under warranty, but since I was curious why the old one stopped working, I disassembled it.

I can't really see which component blew. could it be the transformer?

High res images:

http://andersmusikka.se/burn/whole_product.jpg
http://andersmusikka.se/burn/whole-burn.jpg
http://andersmusikka.se/burn/burn-detail1.jpg
http://andersmusikka.se/burn/burn-detail2.jpg

 

Offline andersjm

  • Contributor
  • Posts: 15
Re: Magic Smoke Release
« Reply #1 on: September 02, 2017, 09:45:00 am »
Looking at it a bit more, it seems like the thin L-shaped trace close to the mains input has blown.

Could they have been using a thin trace as a sort of cheap fuse?

I checked out the diode bridge, it seems to work. The transformer-like-thing (which I think is actually some kind of input filter) also seems okay.

Well, I'm not going to attempt any repair, just curious why it failed.
 

Offline Ian.M

  • Super Contributor
  • ***
  • Posts: 8486
Re: Magic Smoke Release
« Reply #2 on: September 02, 2017, 11:31:22 am »
Either something has gone dead short on the output side of the bridge (or the input filter cap shorted), blowing the 'fuse' track, or the 'fuse' track blew on a switch-on surge.  The plasma then triggered an arc across between L and N, which probably tripped your breaker.   

Check the filter cap and the chopper transistor.  If neither are shorted, repair could be as simple as cleaning the board and fitting a single strand of tinned copper wire of an appropriate diameter to replace the fuse track.  See http://www.gxk.org.uk/info/wire.htm.  If the chopper transistor is shorted, its probably BER, as they often take out the control chip when they blow.
« Last Edit: September 02, 2017, 11:32:54 am by Ian.M »
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf