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