Yet another computer problem thread

I moved my Presario desktop CPU across town last night. At the new place, I plugged it in and found it wouldn't start, just blinked the green LED rapidly. No fans, no drives, no output. I tried the routine of opening the case and making sure everything was still seated, and the trip was very gentle in the first place.

Then my wife mentioned that it did that for about 45 minutes last time the power went out and back on, then it booted up. She just forgot to tell me. Well, this time it was plugged in for a good 3 hours and just sat there light blinking. I unplugged it and figured I'd give it another try tomorrow.

So has anybody had this happen? Has the power supply gone bad? The computer is about 3 years old, and was on most of the time. I Googled terms like Presario power light blinking...There were a number of instances of people with similar sounding problems, but the solutions were limited or contradictory. I would trust anyone here a lot more than stuff I saw elsewhere.

I've had new power supplies go bad, so it wouldn't surprise me. Power outages can be rough on a power supply and I would recommend a surge protector, preferably with a battery backup.
I can't tell you if that is your problem but any good Mom and Pop computer shop can check it out for you.
By the way, take a whiff of your power supply. Get your nose up to it. If it smells kind of 'scorched', then I would bet that it was your power supply.

This *shouldn't* be the answer but is worth checking. If you have a cheap plug-in outlet checker, look to see if the polarity of the outlet is reversed. Most (I say MOST) good eletronics aren't bothered by this but I've seen a few that don't like it.

Compaq Presario?!

Because we were overseas, with the Air Force, our initial two purchases ('95 & '98) were Compaq Presarios bought through the Army Air Force Exchange Service. Both had power supply problems as well, within short order. A new power supply was about 25% of the cost of a new, low cost, Gateway or Dell system. So how'd we fix the problem?

Bought another computer that wasn't a Compaq. Have never had a power supply problem since.

I've got a Compaq Presario laptop (R3000 model). After about two years of use, I've gone through two batteries and one power cord, plus the power cord input slot can't hold the power cord firmly if it's life depended on it. I'm glad that I got it as a gift and therefore didn't have to shell out a huge chunk of change, but when I DO have to shell out a huge chunk of change...I'm not buying a Compaq.

Jason

Pop open the lid on the power supply (what have you got to lose?)

Aside from looking for the obvious signs of magic smoke release, check the tops of the big filter capacitors. If they are swelled or bulging upward, you got hit with a surge.

Unfortunately, most big-brand pc's don't use standard supplies. Some of the "normal" cased Dells do, but you're probably out of luck.

Ken

Of course the power outage event might be a red herring... I've seen similar results from moving a PC. The motion dislodged some dust bunnies which fell behind the motherboard and caused a short. Took a while to diagnose that one but a little compressed air fixed it.

Sounds like the power outage smoked your motherboard. If you are getting a green light then the power supply is still working but could be damaged as well.

Best bet is to take it into a pc shop and have them run some tests on the hardware.

FWIW, PC's and monitors should always be plugged into a power surge protector. A $10.00 power surge protector can save you hundreds of dollars in damages.

InFlight said:

Sounds like the power outage smoked your motherboard. If you are getting a green light then the power supply is still working but could be damaged as well.

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That's not necessarily true. I have had to replace the power supplies on about 45 HP's within the last 2 years at our office. Some go up in smoke, others just do nothing when you hit the power switch, and some just blink the power light when they fail. I miss the old days when I got to decide what PC's we bought. Now the USAF tells us what to buy.

The blinking green light probably runs off the +5V "standby" output of the supply. It is quite common for this output to be OK, and the rest of the supply to be fried. I wouldn't suggest opening the power supply up to attempt to diagnose/repair it unless you have experience in working with high voltage electronics. The input section of these power supplies contain large high voltage capacitors that can store a dangerous charge even when unplugged. The input side of the supply is also not isolated from the AC powerline, and presents a serious shock hazard with respect to earth ground. Unless you have experience repairing switchmode power supplies, the whole supply is best treated as a "black box" and replaced as a unit.

Be very careful if you try replacing the supply in a "name brand" PC with an off-the-shelf unit. Some manufacturers will go to great lengths to attempt to "lock in" replacement part sales by designing parts that are just different enough from commodity parts so that they won't interchange. Even if you can get a supply that looks like a drop-in replacement, some manufacturers will do stuff like using a motherboard connector with a different key arrangement, so the standard one won't plug in. With care, you can make a standard supply work by cutting the plug off the old supply, and splicing it onto the new one.

Even more insidious was one old Dell model I worked on, which used the industry-standard 2 piece connector (this was back in the pre-ATX days), but altered the pinout! If you plugged a standard PSU into the motherboard without swapping the wires in the connector housing (or swapped a new motherboard into the old case and reused the power supply), you let all the magic smoke out of the motherboard. :cry:

PC Power supplies (aka "the silver box") are uber cheesy....especially from a huge OEM like Dell who asserts massive pressure to cut costs.

I wouldn't be suprised that the cap's have failed - there is a major issue with bad caps in the industry. Your 3 year old PC is right in the thick of the issue.

Do be cautious that Dell very well may have used a non standard power supply. Unfortunately there is no easy way to tell.

From the sound of the problem, I would think this is your first place to look.
If you are not handy with a DMM or can't find a friendly repair shop, you can try one of these testers: (https://www.iguanamicro.com/cops24posute1.html) or just bite the bullet and get a new supply.

The above URL is from a store near me - you should be able to find a similar unit in your area.

Best of luck,
FredA

I used to turn off all my computers when I would travel for a few days. I always had problems getting them to boot up when I got home. What I finally discovered is that my system battery would get discharged after my computer was unplugged for a few days. This system battery in my Gateway PC was in addition to the replaceable CMOS battery.

The same thing can happen to older power supplies. As they age they don't recharge as well and can eventually go bad when unplugged for a period of time.

If your Compaq is three years old, I would seriously consider replacing it.
Global Computer has barebones kits from $99 and systems from $370. I bought my gaming system, a laptop, and anything I need to upgrade the other 3 computers around here from Global and they've been great! Better selection, prices, and service then the local mom & pop stores and worlds better then the "super" stores.

You should be able to re-use your monitor, keyboard, mouse, etc. although with Compaq that's not guaranteed.
As far as reusing the hard drive, I'm not sure about Compaq, but I tried to use an IBM hard drive from a Dell in a standard PC and it wouldn't work. Turns out the part number indicated it was a Dell proprietary drive and even though all the connections are standard, the HD controller/Bios on the motherboard has to be Dell for the drive to work. It wouldn't surprise me at all if Compaq did the same sort of s**t.

If nothing else you can get a 350 watt power supply for $20.

Check the heat sink on top of the CPU. The generic P4 heat sink that comes with the boxed CPU is a real bugger to seat correctly and can be jarred loose during shipping or moving across town. If the heat sink is not correctly attached the CPU will instantly thermal trip and appear that the unit it not working.

John

If the non-standard power thing is only "size" related, an inexpensive but reliable replacement may still work great.

My slimline Gateway blew its power supply about 3 years ago and the case design meant the only internal replacement I could use was the special wedge-shaped one designed specifically for this unit. $150. <cough>

I took the power supply to a local parts place and had them verify the power and they laughed, indicating I was the third person that month that had brought one of these in. Ugh.

Anyway, they gave me a $35 generic super-reliable brand that was far too big for the case, but since it was full size it had all it "lengthy" cabling. I just put the power supply behind the computer, ran the cable inside and plugged it in.

3 years later it hasn't hiccupped once. (I love a good 'puter tale.)

Jerry

It's fixed! Between no home computer and moving, it's been a while since I was able to really check the forum. Thanks for all who made suggestions and observations. A number of you agreed it could be the PSU, so I ventured to take it out. Nothing looked wrong, but I figured it must be bad anyway, especially since it didn't power on at all; no fans, no keyboard lights, no beeps, no nothing.

Then, busy as I was I had a stroke of luck. I was with a friend who needed a patch cable. We stopped at a CompUSA store and found they had a store closing clearance. I had previously gathered that I needed an ATX PSU >=250W. So I took the opportunity to pick up a 300W unit for $15.

The connections all fit like a glove in the Compaq computer, and installation took about 3 minutes. I agree that my Presario is a real POS. The Optical drive failed after about a year and I replaced it. Soon after, the monitor color balance went bananas and could not be pursuaded to turn down the RED component less than 100%. Now the PSU failed. I'm not a "computer guy," but this machine has made me somewhat proficient at computer repair.

After all I've had to fix, I'm convinced that if people knew how easy it is to work on computers, the need for service techs would drop by 75%. Sure computers are complex, but the complexity is already built into the components. With a mild dose of research to find out what works with what, putting it all together is very easy, along the lines of building a LEGO vehicle or something.

10fttall said:

After all I've had to fix, I'm convinced that if people knew how easy it is to work on computers, the need for service techs would drop by 75%. Sure computers are complex, but the complexity is already built into the components. With a mild dose of research to find out what works with what, putting it all together is very easy, along the lines of building a LEGO vehicle or something.

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Power supply replacements are easy, at least if you have one that fits. Replacing an optical drive is easy. Replacing a hard drive is a bit more challenging. All bets are off when you swap mainboards... often, the new mainboard will be a LOT different from the old, especially when you use aftermarket parts, and will often have a bewildering number of options to set up.

Well, you've already replaced it, but I've seen PSUs that will occasionally get into a state where they won't want to start up after a blackout or such - the trick seems to be to unplug the PSU from the wall, and try to start the PC. This will drain the caps and seems to reset the problem PSUs so they start again. You may have to try this with the power swich on the PSU in on and off positions.

unplug the PSU from the wall, and try to start the PC.

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I actually did try this, although I didn't know the reason as you explained. I saw it as one of the possible solutions on the web somewhere, where they said to unplug and press the power button for several seconds. I did it because it was easy and didn't seem like it could hurt. It didn't work in my case, though. And the old PSU had no I/O switch, although the new one does.

I'm not recommending this to anyone else, but...

When I come upon a machine that won't light at all, I pull the power plug out of the back of the power supply, and insert a finger into the power supply socket, touching all three contacts. I've never been shocked, and it works about 75% of the time for systems in this category.

But again, I'm not recommending it to anyone else.

Touching the contacts won't do anything except take up some time. If you just unplug the PSU and wait, it will have pretty much the same effect. If I am about to open up a PSU, I typically bridge all 3 contacts with a screwdriver just to be safe, but I've never seen a spark. Most PSUs have resistors to slowly and safely drain the capacitors inside.

I have a cheap (free after rebate) PSU that I'm trying to fix. I shorted out the 3.3V rail (while using it as a bench power supply), and one of the traces on the circuit board melted/burned. I got it partly working by soldering a wire across where it melted, but now the 5V and the 3.3V outputs are both around 4.2V, and change depending on the load. I would never use it in a computer now, but it's fun to try to fix it.

m85476585 said:

Touching the contacts won't do anything except take up some time. If you just unplug the PSU and wait, it will have pretty much the same effect.

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My experience tells me otherwise. When a technician for my distributor first proposed this to me, I said "yeah, right." But later testing has shown that unplugging the power supply and waiting takes longer than touching the contacts, and the latter procedure is more reliable.

I won't venture to guess why it works, but I'm confident it does based on significant personal experience. I've used this procedure since the advent of power management compatible power supplies, in probably a hundred cases or so, and for the first year or two I tried the pull-the-plug-and-wait method first.

Caution - most contemporary switching supplies use front-end caps that are charged to the PEAK-TO-PEAK voltage of the AC line.
Because they are behind (usually) a full-wave bridge, shorting the input won't discharge them.
These MAY bleed down before you get inside - they may not.
Fully charged, they contain enough energy to kill.
Be careful.
Don't kill yourself trying to fix a $30 power supply when it clearly says "no user serviceable parts" -- they mean it this time.

freda said:

Don't kill yourself trying to fix a $30 power supply when it clearly says "no user serviceable parts" -- they mean it this time.

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Now THAT is what I was saying in the first place.