30 May
2008
30 May
'08
7:14 a.m.
(that's why I said 'unlucky -- if you
just replace the transistor, the
new one will most likely fail again at switch-on).
After working on a SMPSU (or any power supply for that matter, but especially
a switcher), I usually power it up to test throught a light-bulb. At first with no load and a low wattage bulb (40w) - Most switchers
won't run with no load,
but you will see the bulb pulse is it kicks - Brightly and solidly lit = investigate
further. If it passes that test, move up to a 100w bulb and just enough load to
get it to regulate.
This is assuming a small (50-100w supply) - if it's a big monster adjust your
"current limit" accordingly.
The 1kW halgone 'secourity lights' are useful as currnet limiters on
larger devices. They proably won't save the transistors, but they will
save PCB tracks, transformer windings, and the like.
-tony