Schematics for HP/Compak NX9110 Notebook Main Board - Page 2

JHEM wrote:



Not strictly true. The full information is still in the filing. Certain
information can be kept off the public record as a trade secret
(exactly what you can get classified this way depends on how well your
lawyer can dance).

What do you see when you look at the outputs of the supplies with a scope?

First thing I'd try is to bridge a big cap at each of the voltage
outputs.  Designers are expecting too much out of filter caps these days.
They go open and the first pulse out of the switch overvoltages the
system. Since there are  multiple feedback and control paths, it's not
always easy to see.

I have a HP LCD monitor with an open cap.  The power supply put out
20V spikes on the 5V line as part of the shutdown cycle.
Fixing the cap fixed the supply, but the control processor has taken
offense and died.
mike