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Dell Inspiron 3700 won't startup (even to BIOS)

Hi,

Trying to repair a Dell Inspiron 3700 laptop. When I turn it on i'm getting the power light on and the caps lock/num lock etc lights flash on. Sometimes I can get into the BIOS but after a while it hangs or turns itself off. Most times the caps lock and other lights stay on and then after 10 or so seconds it powers off.
I've stripped it down to the bare minimum connected components but without success. I suspected overheating but the fan seems to be spinning although its hard to be sure because of how it is arranged inside.
Any suggestions of things I could try to diagnose the problem?

Thanks

rid

Verify battery charge status. It might be a power issue (AC adapter not giving enough power and battery low).
The battery has a row of LED's and a pushbutton for indicating charge; you'll have to take out the battery to get at it
/RID

nobus

try booting it from the battery only, or from the AC adaptor only.
check the cmos battery, it should read 3 V.

ddrdan

That's an odd bird cooling assembly" You have to take everything out of the case to remove it, even the motherboard.

Clean it the best you can while installed, take a tiny round bottle brush to the fan to get the dust from between the blades and the housing. If this is causing a drop in fan RPM it will overheat.

Load a freeware cpu heat monitor software and check for sure that heat is the problem. This is a good free one:

http://www.pcworld.com/downloads/file_description/0,fid,7309,00.asp

ddrdan

I'm sorry...... talk about not reading the question!!!!!! forget the software check

petez5

ASKER

I changed the battery to full and tried it with both AC and battery connected and individually. No change.

I looked around inside for the CMOS battery but couldn't find it. Its a real strange arrangement inside. I see what you mean about the cooling assembly ddrdan. The weird thing is I couldn't actually see a fan of any description. I removed the hard disk and cd-rom and powered on and while the LEDs did their usual thing there was no sound whatsoever. So if there is supposed to be a fan it isn't working. But I don't see why it isn't there if its supposed to be. Any further ideas?

nobus

you should find a cmos battery ! in many cases it is a twin wir leading to it, and all covered in a shrinking plastic tube, it is black in many cases, but that can vary!

petez5

ASKER

eventually found the batteries....there's loads of em! mounted underneath the wrist support bit next to the touch pad.

anyway after dismantling i noticed something odd about the cooling assembly. i was expecting to see a fan on the end of it but there's nothing there. i've taken a picture, i'm sure the fan should be at the bottom right: http://hometown.aol.co.uk/petez5/laptop_cooler.jpg

especially when you take into account this: http://www.parts-people.com/index.php?action=item&id=214

really confused cos i don't see how the fan could just be missing?!?! when the laptop was working fine up until a week or so ago.

any thoughts?

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rid

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petez5

ASKER

Ok thanks for that info. The heat sink is connected to the CPU cooling. So if its not heat related any other ideas what it could be. It seems strange that it comes on for a little while (but nothing on the screen) but the caps/num lock lights are flashing every second or so. THen after about five seconds it goes off. No beep codes or anything. Surely if the motherboard was fried it wouldnt come on at all?

nobus

you can't tell without replacing it; as a motherboard is composed of millions of parts and pieces, any fault can lead to many diffrent outcomes

petez5

ASKER

Ok i replaced the motherboard and now have a slightly different problem. The laptop will boot and seems to work fine. Except only if you have a monitor plugged in. Nothing at all (not even any bootup screen) shows on the laptop screen. I have tried the Fn key to switch displays and that cycles the display options (LCD only, both, monitor only) but nothing ever displays on LCD screen. I went into BIOS and tried altering display setting but no change. You do seem to get a small flicker on the screen just after switching on but after that nothing. Could it be a display adapter issue? Because at one point during my first problem I did get the initial boot up screen on the LCD so I know it works.
Any ideas?

nobus

i suppose you double checked the LCD connection?

rid

Yes, as suggested double- and triplecheck all connections. Also any joints between motherboard and add-on units if any are present should be re-seated to ensure proper connections.

This could also be a dislplay adapter problem as you suspect, or the inverter has chosen to die just now, or a connection inside the screen has become unseated...
/RID

petez5

ASKER

ok never sorted the lcd screen problem but the motherboard worked fine after replacement. points to rid for helping me with ruling out the overheating and fan missing problem.