Member Avatar for amr090

i have a dell 4100 computer on which i just tried installing 2 256 mb ram. When i try to power up I hear the normal hum and power supply start up but my green power Led which normally turns on at boot up does not. also the green led light on my motherboard which should turn on does not. Nothing shows up on the monitor and the monitor light just blinks on and off


I tried putting back the original 128 mb RAM into it and trying to power up but the same result. What could the problem be? Please Help. Is my motherboard fried? what can i do to try to fix it?

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Given 's description (Dell 4100, new memory fitted, PSU audible and drive lights active, but the motherboard/STB LED never comes on and there is no video) and the earlier suggestions from and , here are focused, practical diagnostics to separate a failing power supply from a motherboard/POST problem.

Start with a careful visual and electrical check: inspect the PSU and motherboard for swollen or leaking electrolytic capacitors, burn marks, or loose front-panel LED/wiring. Measure the ATX standby rail at the main connector with a DC multimeter: probe the purple wire to any black wire (ground) and expect about 5 V. If the standby rail is present, the PSU is at least partly alive; if it is absent, the PSU is the prime suspect. With the motherboard disconnected, a controlled bench test of the PSU (short green to black on the 20/24‑pin to force-on) lets the unit be tested for main rails — expected ranges are roughly: +3.3 V ≈ 3.14–3.46 V, +5 V ≈ 4.75–5.25 V, +12 V ≈ 11.4–12.6 V. Use a PSU tester or a meter rather than touching pins; disconnect drives and the board before forcing the supply on.

If the PSU voltages are good, move to a minimal bench POST: board on a nonconductive surface, CPU + cooler, one known-good compatible memory stick in the correct slot, onboard video or a known-working card, and a system speaker for beep codes. Check the CMOS battery and the board for obvious shorts. If the PSU fails the bench test, replace or swap with a known-good PSU before condemning the motherboard; if the PSU tests good but the board still refuses POST, the fault is likely the motherboard or CPU and the unit should be serviced or replaced (warranty permitting). Take electrostatic and mains-safety precautions at every step.

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Member Avatar for caperjack

The Green lite on the board was it out when you installed the ram ,If not you may have fried something ,did you remove the power cord and drain power from computer before you installing the ram!!!

Member Avatar for amr090

yes i did. the led thats not on right now is the 'stb led' the strange thing is when i turn the computer on i can still here the power supply hum and also i can see the lights on cd as its booted. but nothing else happens.

Member Avatar for caperjack

yes i did. the led thats not on right now is the 'stb led' the strange thing is when i turn the computer on i can still here the power supply hum and also i can see the lights on cd as its booted. but nothing else happens.

Sometimes when installing ram you can loosen or nockoff wires check and make sure you didn't pull off any wires ,or hope you didn't short the ram or board with a charge of static electricity

Member Avatar for amr090

i think there may be a power supply problem maybe thats why the 'stb led' is not being lit up
is there any way to reset the power supply?

Member Avatar for caperjack

i think there may be a power supply problem maybe thats why the 'stb led' is not being lit up
is there any way to reset the power supply?

Not that Im aware of ,HP tech support woluld say that unplugging PS and Holding the Power button in for about 40 seconds drains and resets it i think !

Member Avatar for alc6379

Caperjack's suggestion is one thing to try, and here's another:

Sometimes power supplies have circuit breakers in them. Try simply unplugging the system for 2 minutes.

If that doesn't work, disconnect all external devices, unplug all of your drives, remove your RAM, and remove all PCI/AGP cards. Then, see if you get a light. If not, then you've more than likely got either a problem with your power supply or the motherboard. I hope you're still in warranty!

On Dells, that light is called a "flea power" light. It generally indicates that the ATX connections on the board are supplying power, so when you hit the button, it should respond.

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