Dell Dimension 5150 not booting - weird one

[Stu]

I have a client's Dell Dimension 5150 desktop that is not powering on. Nothing unusual prior to it happening, just came to switch on one morning and nothing. Just a blinking amber power switch.

First thought was the PSU, but this checks out OK in another machine, and installing a brand new 400 watt unit in the Dell makes no difference.

I've completely stripped the machine down to rule out any failed components. At the moment it's just the PSU, RAM, CPU, motherboard and front panel switch connected. No difference.

Now this is where the fun and games start. Just for tricks, I decided to try a third PSU I had lying around, a 500 watt job this time. Hooked the video card and monitor back up and tried my luck. It booted! Got POST output on screen and the CPU fan was turning nicely. Turned the machine off to try again, but then nothing. Back to square one and the orginal problem.

By now my curiousity is piqued, so for further laughs I decided to remove the CMOS battery. It then starts every time without it! BUT only with the 500 watt PSU. If I try the same with the original or the 400 watt job I get nothing but the blinking amber power light.

I'm really scratching my head with this one. Initial thoughts are maybe it's not getting enough juice, hence why it will only sometimes run off the 500 watt PSU (everytime with CMOS battery removed), but this can't be right since the original Dell PSU is 305 watts and nothing has been added. Also wondered if it might be the CPU fan, but this runs fine when I do get the machine going.

Any thoughts before I lose my sanity? Motherboard perhaps?

 

[MrMille]

call a priest

 

[tkrabec]

Stu what do the diagnostic lights show?
http://support.dell.com/support/edocs/systems/dim5150/en/sm/tshoot1.htm#wp1120147

 

[focuz]

Alot of times with the dells when the power supply burns out it will send a shock through the motherboard and fry it out with it. So the powersupply most likely blew and put a short circuit in the board around the cmos. Just a guess in the dark without being in front of the machine. The diag lights should tell you more.

 

[Bryce W]

call a priest

LOL

Check the pins on both the motherboard and the power supply. Ive seen a few PC's that had one of the pins bent too far back and thus not making contact. I had tried a few power supplies of different brands and only one worked. Turns out one brand would JUST make contact where the others would (the pin must have been like a hairwidth bigger or something).

Give that a shot.

 

[Stu]

Stu what do the diagnostic lights show?
http://support.dell.com/support/edocs/systems/dim5150/en/sm/tshoot1.htm#wp1120147

Thanks for the very useful link tkrabec, that was most helpful. Although I wasn't getting as far as any diagnostic lights, the flashing power button was indicating a pre-BIOS condition.

Anyway, the problem is now solved. It was, wait for it.....the front panel USB ports! Seems these had seen some serious abuse and upon closer inspection I could see bits missing and mangled wires inside. I cleared the short circuit and machine runs like a dream again.

I guess that's the trouble with USB ports, it is easy to overlook problems with them, particularly when the customer fails to inform you of any prior trouble.

Another one for the book of experience, and I'll be including thorough USB port checks in my troubleshooting routine in future.

 

[cookiefaces]

blinking amber light, need help with front USB ports

I am a novice in the repairing of computers, but my 5150 is experiencing the same problem with the blinking amber light. The previous post by Stu regarding the front panel USB ports does make sense in my case, in that I have had problems with these ports inthe past. I am thinking that this might be the issue in my case. I need some insight into how I could repair/remove/disable these ports. Any help would be greatly appreciated.

Thanks, in advance.

Corey

 

[Stu]

I am a novice in the repairing of computers, but my 5150 is experiencing the same problem with the blinking amber light. The previous post by Stu regarding the front panel USB ports does make sense in my case, in that I have had problems with these ports inthe past. I am thinking that this might be the issue in my case. I need some insight into how I could repair/remove/disable these ports. Any help would be greatly appreciated.

Thanks, in advance.

Corey

Normally you can just unplug the offending USB port's cable from the motherboard and the problem is solved. But on this particular model the front USB ports are hardwired into a special plug that serves all the front panel functions (power button etc), so you lose them all if you unplug this.

The best option would be to replace the entire front panel circuit board to which the USB ports physically attach, but Dell charges a ridiculous amount of money for these, certainly here in the UK anyway, so you'd do well to get one second-hand on eBay or something like that.

In my case, the client didn't want to fork out silly money and wasn't bothered about losing the functionality of the two USB ports; there are plenty more at the back. She asked me to seal the ports up somehow. All I did then was use a tiny screwdriver to prise apart the crushed and mangled wire connectors in the USB ports, and then sealed with black duct tape.

 

[iladelf]

Interesting you mentioned the cause; I've seen quite a few Dells where the front ports were causing an issue. I just installed a 4-port USB adapter as a fix in the past.

Have to watch this with weird Dell errors in the future.

 

[Boeboe]

CMOS battery

After removing and putting back the same battery mine stopped blinking and it turns on again, with post beeps but I'll look into that later.

Boeboe

 

[Blues]

I think I worked on the same model Dell I didn't have any problems except one time with the front USB ports on it. It ended up melting a USB cable and frying an HDD enclosure. The system works fine and I even tested those ports and they worked. The cable was bad wish I had an image of it the thing looked like someone was trying to weld it.

 

[Boeboe]

Happened again but this time the trick with the cmos battery didi not work ( ah by the way, the beeps were of course because the cmos was cleared and I had to remove the floppy and set the time in the config).
This time I managed to get it working through this post:
auzzie.net/cccblog/index.php?title=dell_flashing_amber_power_light_possible&more=1&c=1&tb=1&pb=1
(but I did not check whether it survives a reboot or power off (as it is turned on always anyway)).

Good luck
Boeboe