Another Attempt, Dell Optiplex SX260 Computer Won't Boot Up
 

Hi,

Regarding that small Dell Optiplex SX260 desktop type computer
that uses an external power supply that won't "boot up". Note: There
is a big difference between this SX260 and a GX260 model.

I checked to see if there was any operating voltage for the P4/2.6Ghz
CPU, and I measured 0V across the "bank" of 2200/6.3V filter caps after
I turned on the power. This CPU requires 1.25V - 1.4V to "run".

I measured +12V at the input of the V regulator(s) which I assume operate
as high speed switches (SMPS), but there was no voltage on the other
leads of those switching regulators in parallel.

Using a "low power" (prevents semi-conductors affecting in circuit
resistance readings) ohms meter, I measured about 5.5 ohms across those
filter caps. After I removed the CPU, I measured about 63 ohms. Of course
electrolytic caps normally have some "leakage" current that will affect the
reading.

It seems to me that the 5.5 ohm reading might indicate a CPU defect?

With the CPU removed, there is still no voltage across those filter caps.
I assume the voltage regulator has been damaged by the CPU?

Thank You in advance, John