Dell Dimension 8400 wont boot up

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I had dell come and replace motherboard and CPU, and all is working fine again.

I didnt see any burnt cables or whatever, but that could well be whats causing the problem. I'll just have to wait and see if it happens again while using my current PSU.
 
I havent looked at this forum since i repaired my daughters Dell. After replacing the motherboard we had and still have another issue. The PC restarts on shutdown. I have read a few forums to see if others had the same problem and it looks like they have. I have tried all the advice mentioned and still have the restarts on shutdown. My advice to anyone wanting a new PC. DONT BUY A DELL
 
This problem seems really weird. Maybe it's just luck but my 8400 has had no problems in it's two plus years of service. My question is, have your tried reinstalling windows? A fresh install can cure many woes. (worked wonders for my 4700. dropped processes down from 70 8O to 32).
 
HI
No I havent tried to reinstall win xp pro but i will i visit her in a week or so. Will let you know how I go. Thanks for your posting.
 
I "inheirited" a Dell 8400 from my brother, when they upgraded. There were two known problems from the get-go..first NO memory. I put in 512 mb of memory. Second there was a connector from the face plate to the moBo damaged so I replaced that. Now the machine is intact - power on, power supply fan starts lights blink, no go..doesnt power up, doesnt blink amber, nothing. I just ordered a PS hoping that will be the last thing I need to replace. In anyones "professional" opinion does it sound like a PS problem? Powers up for less than 2 seconds. Back lights blink then go black.
 
I managed to reinstall windows xp sp2 but it didnt make any difference. the pc still reastarts on shutdown. One of these days I will do a complete format and reinstall. Maybe that will solve the problem. Anymore advice will be helpful.
The only advice for HudVal69 is that I think you need a new MOBO.
 
My 8400 has been running quite well for about 2 years it seems like everybody else's and is still on warranty. For about 2 months or so, the fan is running loudly and is not dirty. I go to turn mycomputer on when i get home and the light is solid amber w/ no led's in the back on. Turns out, when i call dell and they walk me through troubleshooting it, theres a power supply to the motherboard (the one closest to the fan w/ 4 prongs) the cable is burnt up. They guy at dell tells me hes sending me a whole new tower and that i can just plug my current hard drive into it. Just hope that can help someone else out there and am also wondering if anything will be different on my new cpu even with the same hard drive as before. ie. settings/information/software.. thanks
 
I am pretty sure that all will be the same.
It was with my daughters when i replaced her MOBO.
You are lucky that you had the extended warranty.
 
My 8400, 2yr - 3mo old, suddenly didn't power on at all. No external lights front or back, no sound, no fan, nothing changed when I hit power on. Opening the case there was a small green light on motherboard; all looked OK. I first followed procedures on Dell site and then called. After a bit more than the site tests, the tech support concluded that it was the motherboard and suggested I buy another from them. This is expensive (out of warranty) and I wasn't fully convinced that was the answer. (I've since seen that 3rd parties offer the 'mobo' more cheaply). So I brought the 8400 to a local Geek Squad. They looked at it for several minutes and then pulled and reseated the cpu. They'd seen that loose before on a 775 board. This worked, all rebooted and came up OK. When I got home the 8400 was in the nothing at all status again. I brought it back and this time they also pulled and reseated the CPI boards. Again all OK. I was extremely careful driving home and all was good at home. A few days later (after cleaning lady (a factor or not??)) it was (is) absolutely dead again. I suppose I should just go back to the Geek Squad, but thought I'd try to see if I could learn more on-line. However my pattern seems just slightly different than others' experience above in this forum and likely the devil is in the details. Maybe the 'mobo' is the problem but maybe not - I and wondered if anyone else has more experience/knowledge about this OK/totally dead/OK pattern. Thanks much for ideas.
 
Add me to the list. Exactly the same problem - fried CPU. I had my 8400 about 3 years and 2 months before it finally started having all the symptoms you guys have had. I mainly use it for video editing and rendering. I did install a small room fan in the cabnet where the computer lives (err, lived). Could be the external cool extended its life? Who knows. Probably a bad design in reqard to heat management. My solution - I just bought another Dell. Lets hope the Core2 duo E6500 is a better processor!
 
OUCH! I just had the exact same problem... after 3yrs 8 months.
No Status lights coming on and amber power light. The fan whirs and the LED on the motherboard lights up. However I noticed that some air inlet vents were blocked up with fluff - this could have caused the CPU to overheat. Longshot though... will see if I can get a cheap CPU to try, otherwise i will bin the PC. ;/
 
I have similar problem. i power the computer on and the fan revs real high but monitor stays black. usually i have to hold the power button in to shut it off turn it back on a few times this way before the computer turns on normally. it resumes normal usage and works perfect.. you can turn it off and back on like normal.. but if you turn it off once it starts for more than 30 minsutes to an hour or so.. once the comp cools down the problems boting it up starts again. It seems to me liek a cpu or MoBo problem but took it into geeksquad to have it diagnosed and they ran software/hardware analysis on it and found nothing. so now we are stuck as i don;t want to spend money on a solution that won;t work seeing as it could be more than one components that is causing the problem( cpu/mobo/powersupply/ect.). i am hoping i can find someone who knows WTH they are talkign about.
 
I have the same problem, the fan sounds like an aircraft building up to take off.
Get the PC in a good light (fluorescent) and look at the capacitors, they should be straight sided cylinders. If ANY of them look "fat" then it is a new motherboard you need. The capacitors swell up inside (like a really old zinc/carbon battery) and stop performing as they should - new motherboard.

I'm trying to troll through the web looking for a replacement.
Spec from Dimension Manual & Dell forums;
Intel 925X Express or Intel 925XE Express, Socket LGA775, System Clock 800 or 1066 MHz data rate (depending on your processor), MemoryT ype 400- and 533-MHz DDR2 unbuffered SDRAM
The most important item is the LGA775 Socket Type, any other and your CPU will not fit.
You might buy a new motherboard & CPU (some places do bundles).
Whatever you do check that the replacement will fit the fan hood.
 
I couldn't find any motherboard which would physically fit in the case and line up the Graphics PCI slot.

So I decided to buy a full size ATX board and a new ATX case. Hopefully the Dell power supply will fit in the case I get (or can be "persuaded") but the heatsink fitting will be a problem, I may need to get a new heatsink/fan assembly as well.
I bought a Foxconn 945P7AD-8KS2H ATX Motherboard, via Amazon for £46.
I'll let you know what happens.
 
Been watching this thread for months. My 8400 had the same symptoms--no boot, CPU fan sounding like a turbojet, just months out of my 3 year warranty. Started happening intermittently then just gave out. I started with the cheapest part and worked my way up (all purchased on ebay)--new heatsink tower, PSU, CPU, then motherboard. Of course it was the motherboard.

But someone in this thread mentioned something that I should have keyed in on--"bulging" capacitors. I was thinking of something like bulging out the sides or scorch marks. No. My old mobo had capacitors with rounded tops--kind of bullet shaped instead of flat-ended cylinders. If I'd paid closer attention I would have replaced the mobo first.

Ironically, a couple weeks later the PSU went out (simply no power except flashing yellow light on power button), but fortunately I had a new spare already!

Good luck everyone.
 
Just to add that I found this forum today because I am having the same problem with my 8400. It's encouraging to know I'm not the only one, but discouraging to see how hard it may be to fix!

Oh, and by the way, the warranty period expired one month ago.
 
These problems all stem from one thing: heat. The early P4 prescotts used in these Dells were simply too hot, and consumed too much power, especially in conjunction with a decent graphics card, for the stock PSU to handle in the hot environment. Dell's stock cooling solution was inadequate for these Prescott CPUs. Dell chose quiet operation over effective cooling, and the price to pay for such a decision is rapid component failure, namely the PSU, CPU, and mobo. Dell's earlier Dimension series, the 4500/4550 line and 8300, did not suffer these problems, as they were equipped with cooler running Northwood P4s.

Also, sucks that you all own Dimension 8xxx series towers. Their proprietary mobos make it impossible to put in aftermarket mATX mobo, or to put the factory Dell mobo into a better ventilated aftermarket case. You could try an get a mobo tray from a Dimension 4500/4550 series, as it supports aftermarket mATX mobos, but even then the unique all-in-one front panel connector is a serious hurdle to overcome. In short, the Dell 8xxx series, and especially the 8400, are poorly designed computers.
 
I, of course, have the same issue. My screen froze and I had to unplug it from the wall to shut it down. When I tried to power it up again all I got was the steady amber light. I went through dell support and pretty much unplugged everything and plugged it back in. It seemd that unplugging the PSU from the mother board is what did the trick. It worked fine for a day and the same thing happened. I unplugged the PSU again and it worked for about 20 minutes and the same thing happened. I'm going to replace the PSU tonight. I will let you know how it goes. I am not even close to computer hardware savy, so this has been an adventure 🙂
 
Add me to the list, what is so galling is that when I bought my Dimension 8400 in 2005 it was promoted as a top spec machine (and top price) but so many of them can't make their third birthday. It's a disgrace.

I had same symptoms - no boot up, just a mad fan on turning the power on, and for me either no lights or just the "B" diagnostic amber light (this configuration has no reference in the diagnostic light tables!).

It wasn't my PSU, but from this forum I know it is either the MOBO or the processor. On removing the processor I found one of the connectors underneath either damaged or melted.

I salvaged the memory, graphics card, and SATA disks and PSU and chucked the MOBO. I'll build a new one from (not Dell) parts. The MOBO had to go as it is damaged, but there's no point re-using the CPU is it runs too hot which caused the problem in the first place.

Oh one more thing, I've kept the heat sink and CPU for prosperity. The sink is a big ugly beast and compared to the wafer thin CPU looks ridiculous, it'll be in a museum one day and people will go "no, never!!"

 
I have a 4700 with a very similar affliction - front panel amber light comes on at power up, power supply fan is going, but not much else. Several months ago I called Dell support and the diagnosis was a failed mobo. When I replaced it, things did work, but during the swap I noticed that two of the connections on the P2 connector were charred. I decided to "clean" (scrape using the end of a large paperclip) the inside of the two charred P2 connectors and also the corresponding pins on the mobo. This exposed enough conductive surface to get more months of service from the original mobo (I just had to clean them again). I've also been turning the PC off every night (it used to run 24x7) to slow the deterioration rate.

However, as noted in earlier messages, the real problem appears to be too much current draw through pins 3 and 4 of P2 (12VDC - http://www.webmadeeasy.net/ComputerDocs/Dell/Dimension/4700/ServiceManual/techov.htm).

The CPU is a 3.2Ghz Intel P4. Is there a different/newer CPU that will fit the socket/heat sink configuration in the 4700 and draw less power?

I could buy another power supply (just to get a new P2 - what a waste!) and install the refurbished mobo, but that would just postpone the inevitable P2 deterioration since I'd still be using the same CPU.
 
Ok, it's been a month since anyone has posted but ill give this a shot.
Im in the same situation, I have a dell dim 8400 that wont start. It gave me the loud fan, the frozen screen just like most of you other folks. Im not unfamiliar in terms of doing repairs myself but this had me stumped until I found this forum (for that im grateful). Anyway, ive read everything written here carefully and there seems to be some confusing info maybe someone can clarify for me. Is it, or is it not possible to relace the mb and cpu on this thing with after market parts? One highly rated member eluded to the fact that they would not fit the original case, while others say they have replaced their parts. If it is possible can someone please tell me exactly what model mb and cpu out there that will do the trick... I dont have the $$$ to buy a new pc and unfortunately i depend on the 8400. I have an online data entry job and its been a pain in the *@#...

Here are some tech specs on it for you much needed help:

CPU:
P4 541 (3.2 GHz with EM64T technology)

Thank you for any help!
 
You cannot replace the MB in the 8400 with aftermarket. Simply won't screw in. You can replace the CPU, but the factory motherboard restricts you to Pentium 4 5xx or 6x0 cpu, no Pentium 4 6x1 CPUs will work, and no Pentium D/Core 2 Duo will work either.

The cheapest way to repair your 8400 is to do the following: buy a cheap ATX case, a cheap LGA 775 heatsink, and a cheap LGA 775 motherboard. Swap over the CPU, ram, PCI cards, hard drive, CD drives (even power supply if you wish) into the new case. Use your old Dell XP CD to install Windows XP, then call Microsoft to activate by phone, give them the product key on the side of the Dell case, and tell them you had to replace the motherboard due to failure. Total cost for the Case, motherboard and heatsink should be a bit less than $100, which is about the going rate for another 8400 motherboard, but if you buy another oem board you're not fixing the source of the problem and just setting yourself up for another failure down the road.

My recommendations:
motherboard: $50
http://www.newegg.com/Product/ShowImage.aspx?Image=13-138-125-02.jpg%2c13-138-125-03.jpg%2c13-138-125-04.jpg%2c13-138-125-05.jpg%2c13-138-125-06.jpg&S7ImageFlag=0&WaterMark=1&Item=N82E16813138125&Depa=1&Description=BIOSTAR+G31-M7+TE+Micro+ATX+Intel+Motherboard

Case: $34
http://www.newegg.com/Product/Product.aspx?Item=N82E16811147064

Heatsink/fan: $14
http://www.newegg.com/Product/ShowImage.aspx?Image=35-119-092-03.jpg%2c35-119-092-04.jpg%2c35-119-092-05.jpg%2c35-119-092-06.jpg%2c35-119-092-07.jpg%2c35-119-092-08.jpg%2c35-119-092-02.jpg&S7ImageFlag=0&WaterMark=1&Item=N82E16835119092&Depa=1&Description=EVERCOOL+EC-PT12-9525EA+95mm+Ever+Lubricate+CPU+Cooler

Total price: $97.95

That should work well, as long as you don't have more than 2 PCI cards or more than 2 sticks of ram. There's a chance that it's the CPU to blame and not the motherboard, but that's very, very rare. 9 times out of 10, it's the board that went bad. Good luck
 


This thread has been a well of information. I too have a Dell Dimension 8400. But I have experienced a slightly different problem. My Dell doesn't do anything when I try to power up. No fan, no lights nothing. I have checked the power strip and cord, all are fine. Inside the case when its plugged in I see the small green LED light on the mobo, other than that its a boat anchor.

Over the last 6 months or so I would have trouble using the reset button when the computer froze. I would have to unplug it to get it to cycle. About 4 months ago, while at work, my Girlfriend told me that it made a lot of noise like a jet engine taking off, much like what others have described above. She had to unplug it to get it to stop and since then its happen a few times. The last time i had to shut it down before this, it didnt want to come back on for a little bit. started to power up then went dead, waited a little bit and hit the button again and it booted up fine.

Am I correct in thinking its either the power supply (probably not) or the Motherboard (most likely)? I am really considering Joefriday's solution about just getting a new case, fan and mobo to solve the design flaws of the 8400 case. Or should I just get the dell mobo to replace it? Money is an issue :) but this replacement solution looks like it comes with a lot of benefits and want to know how hard is it to do?

Thanks for all replies.
 
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