OT: help... - test-drb@ccmp.vtda.org

29 Dec 2000

From: Tony Duell &lt;ard(a)p850ug1.demon.co.uk&gt;

...
 Oh, they're no worse (for HV) than any other
mains-powered SMPSU. We've
had this discussion before, but I still maintain that the most dangerous
voltage in a monitor is the rectified (and maybe doubled) mains -- 400V 

This one uses only direct mains (160V).  That bothers me less as it
can't reach out abnd get me.

...
 at essentially unlimited current. And it's on bare
PCB tracks. A lot more
...
 likely to do you harm than the low-current 25kV EHT
supply that's
impossible to touch by accident. 

There is insulation breakdown, I've been nailed once.

I have experience with HV and High Power as well as big RF so I know
how to avoid getting wacked.  I just generally dislike working on
TV/monitors.

...
 As you doubtless realise, you've got a SMPSU
that's shutting down because
...
 it thinks it's overloaded. 

...
 From testing that woudl be the case. 
...
 The most likely cause of a real overload is a shorted
HOT (Horizontal
Output Transistor), possibly damaged because of shorted turns in the
flyback transformer. So testing that transistor (on a heatsink near the
flyback) is a good first move. 

Testing is that it's ok.

...
 The other thing that monitors suffer from is dried-up
electrolytics,
which therefore have a high ESR. These can cause all sorts of faults, 

the test was to bridge the likely candidates.. no joy.

...
 including a PSU that keeps on shutting down. I'd
test all such capacitors
...
 in the PSU area. This might even be the cause of the
long warm-up time. 

Would seem that way but that was before, not it does not power up.
Since it's SVGA and prints for it are unlikely and some of the parts are
oddball enough to not warrent digging too deep.

Allison