Member Avatar for Farao69

My Dell Dimension 9150 worked well yesterday but today when I turn it on it freeze during the POST, the status bar under the Dell logo on screen go up to 95% more or less, emit a constant beep and the Diagnotic Lights 1 and 4 light up.

I unplugged the keyboard, mouse, HD, DVD, monitor and video card and I still get this error.

Any idea?
Thanks

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  • Latest Post Latest Post by rubberman

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Short expert summary and what the LEDs mean: the Dimension 9150 uses four numbered front LEDs plus POST beep codes as the primary hardware diagnostic. The official service manual explains the LED/beep diagnostics and gives memory/graphics/USB/power troubleshooting steps. (manualslib.com)

Why this can still be fixable (don’t jump to a new motherboard yet): a continuous tone during POST can be caused by either a stuck/shorted keyboard or front I/O (USB/power) wiring, or by an internal fault such as a system-board error. Both causes are commonly reported for Dell boxes of this era, and many users who see “lights 1 and 4” with a POST hang report a board-level failure — but first run the isolation checks below. (minuszerodegrees.net)

Practical isolation steps (safe order, do one at a time):

  • Power off, unplug AC, press power button 10–15s to discharge. Ground yourself.
  • Remove the front I/O assembly (power/USB/headphone block) and its cable to the board, then try a minimal POST with only PSU, motherboard, CPU+fan, one known-good RAM stick in the primary slot, onboard speaker attached. The 9150 manual shows how to remove the I/O panel safely. (manualslib.com)
  • Test memory: try one module at a time in every slot (reseat and retry); if any pass, run extended diagnostics or memtest. The service manual explicitly recommends this modular memory isolation. (manualslib.com)
  • Clear CMOS (use the jumper or remove the coin cell per manual) and retry; BIOS/NVRAM corruption can cause POST hangs. (manualslib.com)
  • If you still get the same continuous tone + 1&4 after the above and with a known-good PSU/RAM, the fault is most likely the system board; many forum reports reached the same conclusion and proceeded to board replacement. If uncertain, stop and get a local shop to confirm (swapping in a known-good board/PSU is the definitive test). (forums.tomshardware.com)

Notes & cautions: don’t probe the PSU internals; when disconnecting the I/O or system board parts follow the manual and avoid static discharge. If any step produces a different beep pattern or text on-screen, record it (or a short phone clip) — that detail will speed diagnosis.

Recommended Answers

All 6 Replies

Member Avatar for finito

constant beep?

Hmm is it coming and going or just is it a continuous tone. Like when you pick up the phone?

Can you try and remove all peripherals and leave just the processor and motherboard (and PSU ofc). Remove the RAM as well.

you should hear 5 or 4 beeps and then nothing.

If you are hearing a siren then that is for overheating of the CPU, but if it was that then the machine would immediately shut down.

Member Avatar for brian1

A constant beep means it can be a memory problem also. you can try troubleshoot system memory then see is there any improvement or not.

Member Avatar for mjdodd

It can also be a stuck key on the keyboard. When the POST tests are done it tests keyboard and if a key is making constant contact it will produce the continuous tone.
M

Member Avatar for Sunnyrepairs

It might be the problem of processor or ur keyboard

Member Avatar for kenkit

IF all the above don't work try and disassemble the whole system unit then return it back again dusting it.

Member Avatar for rubberman

A stuck key can do this. Try booting with everything external (including keyboard and mouse) disconnected, except the monitor.

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