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CPU turns on after many tries of switching power supply on and off

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November 6, 2011 4:39:54 AM

Hi everyone !

My computer is Dell Inspiron 535, nearly 2.5 years old and heavily used since (almost 7 am to 11 pm everyday). It has not been "touched" by anyone or has had any other problems other than this.

For a few months, this is how I have to start my computer in the morning:

1. I switch on the power supply to ups, a green light at the back of the CPU turns on (monitor, speaker, etc. also turn on) I press the switch of CPU, nothing happens. (Fans etc don't start and no other indication is given by the CPU except the green light)

2. I switch off the power supply and everything excluding the green light of CPU turns off. The green light turns off in a while, and then I again switch on the power supply and push the switch for CPU. (Nothing happens)

I repeat these 2 steps a number of times (on-pushSwitch-off-on-pushSwitch-off....), and within about 15-30 minutes of trying the computer turns on (fans,lights get on and windows starts). Sometimes when the computer turns on, it makes a somewhat loud noise like that of engine starting (fans ?) and then it returns to making the usual sound. Everything works normally then, once it is on.

If I turn off my computer at this point and switch off the power supply, and turn it on say, after 15 minutes, it gets turned on with much much less effort and many a times in one try (which is what should happen)

Another thing is that if I keep my ups (and its power supply) on for the night (but the computer is shut down) it turns on normally the next morning when I push the CPU switch. (in one try)

Any idea what might be wrong ? (Switch/power supply unit ?) And is this something I can fix, or shall I call the dell guy only ? (Can I take everything apart in a dell computer just like an assembled computer ? I can see some rivets, I dont think I can take them out...)

Thanks a lot in advance !!
a c 111 ) Power supply
a c 186 à CPUs
November 6, 2011 6:32:48 AM

are all the power cables plugged in correctly?
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November 6, 2011 6:52:04 AM

The batteries in a ups only last a couple of years. It's usually cheaper to buy a new ups than replace the batteries.
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a b ) Power supply
a b à CPUs
November 6, 2011 7:24:09 AM

It looks like the PSU is at fault, theres a resister that goes open circuit on the big HV Caps, if your PC has a reset button try holding that then pressing the power and releasing reset after 4-5 secs.
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a b à CPUs
November 6, 2011 7:40:00 AM

UPS should remain on at all times as it keeps the battery charged. You might try taking the UPS out of the loop and just plug the computer into the wall or power strip and letting it stay like that overnight. Then see what happens.
Like hairystuff says, could be the PSU as well.
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November 6, 2011 11:50:44 PM

Thank you for your replies !

amuffin, the power cables are working correctly, I even tried a different power cord.

I once tried directly pushing the plugs in the wall (not UPS), but the same thing happened...though I havent tried exactly what DelroyMonjo has said (plug the computer in the wall and letting it stay as such overnight). I'll try that tonight and get back to you.
I'll also try what hairystuff said, maybe thats an easier way to start the computer.

By the way, if the PSU if broken, can it be repaired ? Or it has to be replaced entirely (can one do that on a dell computer?)

Thanks again !!
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a b ) Power supply
a b à CPUs
November 7, 2011 3:13:21 AM

Most likely a PSU problem.

Dell usually sends out PCs with barely enough PSU to power everything.

That being the case, a few years of capacitor aging and they often fail.

You CAN use a different PSU. Pre-2000ish DELL used non-standard pinouts and if you put a non-dell PSU into some DELL computers it would fry the motherboard.

Post 2000, I haven't heard of that problem anymore. I have personally replaced a lot of post 2000 DELL PSUs with non DELL PSUs and every one of them worked fine (until the replacements also got too old and had to be replaced yet again).

The biggest problem now is that in DELL cases the place where the power cord plugs in is non-standard. That means you may need some metal cutters and some tolerance for ugliness in order to make a non DELL psu fit in the case.

Either that or pay twice as much money for the same wattage buying a replacement part from DELL.

If you are still in warranty, feel free to tell them to send you out a guy with a new PSU.

I would hazard a guess it is at least 75% likely to be the PSU based on what you said so far.
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November 10, 2011 3:32:33 PM

Thank you for your responses !

UPDATE: I am not even able to open my PC now. Seems like the problem has aggravated somehow, and after 2 hrs of trying I was not able to start it up this time and I have given up.

I asked Dell people and they charge way way way higher than I expected. They said they will charge me nearly Rs. 15,000/- (thats nearly $ 300 !) where they also give me a one-year extended warranty which I dont want. Also, I asked them and one more person, and they said that the motherboard is faulty. (I gave them the same explanation as I gave you guys here). How probable is that the motherboard is at fault? And they always referred to PSU as "SNMP", is that the same thing?

So, I am going for a replacement myself. Ok. There are a few questions now.

1. How do I know what motherboard to choose so that its compatible with the CPU?
(In fact how do I know my CPU I know it Core 2 Duo, E75XX, but I dont know the specific number....? Also, on the motherboard, certain things are written like- "PCI Express", "DDR 2 800", "686 AMIBIOS",etc. are they of any use in this regard?)

2. How much does a PSU cost ? Is it worth trying to first bring just the PSU (and not the motherboard) and see if the computer is working ? Also, what model/wattage PSU should I buy ?

3. In the worst case, if the motherboard/PSU i buy dont fit in the dell chasis, I can always buy a new chasis and transfer the parts from Dell PC that are working fine on it, right ? I mean being a dell computer doesnt means something is "hardwired" into the chasis/motherboard and hence I cant transfer it?

Again, I am telling as much as I know about the PC config:
Dell Inspiron 535
Core 2 Duo
3 Gb RAM (DDR2 i think)
ATI Radeon 4350HD


If you want, I can post a picture of the CPU from the inside, from a camera.


Thanks a lot for all your help once again !!
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a b ) Power supply
a b à CPUs
November 12, 2011 4:33:23 PM

A core can generally only be upgraded as a single unit. By core I mean the combination of processor, motherboard, and RAM. If you want better of any of these 3 you usually have to get better things of all 3 kinds at the same time.

If you are just replacing a part of the core, you can usually just switch out one of those items as long as the other two stay the same and you ensure that whatever is written on the 2 non replaced items is also written somewhere on the new item.

A core 2 duo E7500 processor goes in an LGA775 slot. Any motherboard you get will have to have that written somewhere on the packaging or else it won't work.

You would have to look at the specifications of the DELL RAM (you can find this on their website if you go to home, support, and type in your product code that is labeled right on the side of the case. Somewhere in the sea of product manuals it will say ram numbers on it like 9 - 9 - 9 - 24 or something and somewhere else it should say DDR2 800 or something like that. If it says DDR2 800 on the motherboard then it is likely that is what it will say in the documentation, but it doesn't hurt to verify this. It also doesn't hurt to look for the series of 4 numbers with dashes in it like I showed above. Any new motherboard you would be able to use should have similar numbers in its documentation.

A PSU costs $1 per 10 watts. If it says it is a PSU and it costs $1 per 20w then it is lying and what is in the box is really a ticking time bomb that may take your expensive parts with it.

I don't see any good reason you should not try an Antec EarthWatts 430 before you buy a new motherboard. I would also recommend that specific one the absolute most for low end systems.

If you buy a non-dell power supply it most likely won't fit in the dell case.

To address this, you can use metal cutters and actually cut away the metal that will be obstructing the plug in port in the PSU when you put it where it will eventually be (potentially this costs $0, but it may not look pretty depending on the tools available) or you can just buy a new case.

If you intend to pay for a low end case in order to have it look more pretty, Cooler Master makes reasonable low end cases without a lot of bells and whistles that are cheap and do the job.

There is no good reason that you can't just unscrew or otherwise unlatch everything from the DELL case and put it in any random case, everything except the PSU plug in port should line up exactly like it does now.

Some DELL motherboards have a sliding in feature. If you have one like that, it should still have universal screw holes that you will be able to use in the Cooler Master cases.

There are not any cables that are soldered to the same cable such that the devices cannot be physically separated. All cables will disconnect from at least one end.

Anyway, try getting an Antec EarthWatts 430 PSU first and leaving the core alone. If it still doesn't work, then come back and I will work with you more about what to do with the core.
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November 22, 2011 12:13:53 AM

Thanks Raiddinn ! I havent been getting much time lately (got my exams going on), so I havent bought the PSU yet. I will buy it in a week or two and get get back to you guys. I posted this so that the thread doesnt die.

Thanks again !
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December 27, 2011 11:46:42 PM

Thanks A LOT guys !!

I went ahead and finally bought a 450 watt PSU. I couldnt find the one Raiddinn said, so I got a different one. As long as it keeps working for another year and half or so its ok...I dont plan on keeping this PC for long anyways.

Its funny how simple changing the PSU really was... :kaola: 

Thank you once more, for you guys have saved me a lot of money, and given me the confidence to assemble my own computer in the near future !!

Cheers !

:D 
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December 27, 2011 11:48:32 PM

Best answer selected by hypernova.
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