Is there any capacitor "built-in" inside the secondary of the transfo ?

I'm trying to mesure the impedance and it looks open.



"conundrum" wrote in message
oups.com...
On Jun 17, 7:26 pm, "rb" wrote:
"Jim Yanik" wrote in message

...



"rb" wrote in
:

"JW" wrote in message
. ..
On Fri, 15 Jun 2007 11:51:30 -0400 "Max" wrote
in
Message id: :

Inverter has been confirmed bad. I don't have any output from it.

What usualy go bad with them ? Transfo , caps ?

In my experience, FET's and picofuses. As Michael has said, often the
picofuses go for no reason - replace 'em and you're often back in
business.

Is it a kind of switching power supply ?

Yes. The step-up variety.

Anyone ever fix one of the Sony inverters?
Tokin S405-b001-z1-0 ???
Rather hard to tell what's what.

Can you find a datasheet on the inverter IC?
They usually have a circuit that's close to the end product.

--
Jim Yanik
jyanik
at
kua.net

Haven't tried that,will give it a try, thanks Jim



I've also seen the switching transformers on laptop inverters
internally short. Usually this results in an inverter which runs
(badly) but overheats the drive IC(s) and causes them to shut down
within seconds.

Only way to test these suckers is by isolating each transformer in
turn, on most inverters this will result in a shutdown but there will
be a brief burst of light from the tubes connected to the good
transformers.

The other slightly more annoying failure mode is for one of the drive
transistors to short under load. Here, the test is to measure the
temperature of the transistor pairs, the bad ones will get MUCH hotter
than their neighbours.

In either case, always replace the primary smoothing capacitors even
if they look OK, as the latter failure mode often results from dried
up caps.

Regards, -A