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

Hi,

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:

>Hi,
> My brother gave me his "dead" Compaq Armada 4210T laptop to repair.
>I normally service TVs and other stuff. With fully charged battery, when
>I turn it on (push power button), almost nothing (no hard disk spin or floppy
>disk drive noise (with floppy in drive), no "beeps" or lights, no display
>(even with external monitor)) happens when you turn it on except 4
>(power, caps lock, scroll lock, numb lock) of 5 LEDs light up.
>I removed the battery, but the same thing happens using only the external
>power source.
>
> With the room totally quite, if I put a floppy disk in the drive, I can
>hear a faint noise when I turn on the power (but floppy drive doesn't run).
>If I remove the floppy disk, it isn't there.
>
> I measured +5 volts (after power turned on) at one of the pin connectors for
>external keyboard, which tells me that the internal DC to DC inverter
>is "running".
>
> This failure wasn't the result of a power surge, as in a storm. No advance
>warning of any kind and the laptop wasn't dropped or abused. I thought
>possibly a static discharge from his body after walking across a carpet, but
>he said, he doesn't recall that event?
>
> I opened the unit and found a tiny 5A fuse, but that tested good
>(not open). I examined circuits for bad solder joints. Also checked for
>loose connections of any kind.
>
> If you ever had this experience, please tell me what you did to fix it.
>
> Thanks in advance, Brad
>
> Before you type your password, credit card number, etc.,
> be sure there is no active keystroke logger (spyware) in your PC.
>

Brad wrote:
> Hi,
>
> 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

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
behavior.

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
there.

Otherwise, good luck finding a schematic.

Paul