UPDATE: Dead Compaq Armada 4210T Laptop (more details)

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    Part of the internal DC-DC inverter (SMPS) is not "running" which I assume
powers the drives (HDD and floppy), etc.  There are three transformers and
using a scope with a pickup loop, one of the three transformers is not
"switching" with laptop turned "on".

   Note:  LEDs that are on, cannot be turned off using their related key (eg.
Caps Lock).  See details in my previous post below.

    I have searched everywhere for a schematic. I have the "service manual"
(.PDF file) for this model, but it doesn't have schematics.

    I tested (in circuit) the parts in the internal  DC-DC inverter and I have
not found a defective part.  Checked all solder joints.  It is possible that
an outside "control" that normally activates the SMPS is not functioning.

    Does anyone know where I can get a schematic for this or a similar
model laptop?

                   Thanks in advance,  Brad

On Fri, 16 Feb 2007 13:58:26 GMT, you wrote:

Quoted text here. Click to load it

Re: UPDATE: Dead Compaq Armada 4210T Laptop (more details)

Brad wrote:
Quoted text here. Click to load it

Some switching devices have things like overcurrent protection,
and can shut down the switcher very quickly. I liked how some of
those worked in the past, where they stayed in "hiccup" mode until
the fault was removed. You could still see some signals from those,
as they patiently waited for the fault to go away.

For debugging purposes, a unit that shuts down instantly, means
needing something like a digital storage scope, to watch the startup

If you want to trace how a circuit works, start with the chip numbers.
Many companies put a reference circuit in their datasheet, with
instructions on how to tune the switcher, select coils and caps
etc. Using the reference schematic, you should quickly be able to
figure out a few things. So find the switching chip, and work from

Otherwise, good luck finding a schematic.


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