Laptop Killing Power Supply

I have a fairly old Compaq CQ70 laptop, it has an overheating problem which i intended to fix by stripping it down and cleaning it and applying new thermal compound to the cpu cooler. More recently the power jack was not showing as plugged in, so i was holding the cable a certain way for it to connect, i was thinking of replacing the internal terminal part to fix this. Last week i was getting no power to the laptop at all, i checked the power supply using a multi meter and i got nothing, i ordered a second hand one off ebay, i tested it with the meter and i was getting power at the jack end, i plugged it into my laptop and started it up holding the cable up whilst it booted into windows, next thing the laptop went dead. I tested the power supply and it is now dead.

Does anyone know what could be causing this, is the laptop goosed or could the loose internal terminal be the cause?

cheers guys

 

Sounds like a bad power port? Have you replaced that yet?

 

No i have not, i was hoping someone could help me find the possible cause before i risk buying another power supply. Is there an internal fuse in the power supply?

 

A power supply should have some sort of breaker. However, assuming that is has the right Voltage/Amperage needed for your laptop, I'd bet on something in the laptop shorting the PSU and tripping the breaker.

 

Yeah the power supply had the right voltage and amps. I hacked one of the power bricks and i did not see any obvious fuse. I have removed the power terminal port from my laptop as it was loose. It looks like ill have to replace that and hope it wont cause another power supply to break.

 

Just like you have discovered, it sounds like you need to replace the power jack in the laptop. When you need to hold the cable a certain way, and two power supplies suddenly died, that is a dead giveaway.

In this case it would be a fuse that was blown, not a circuit breaker that was tripped. Also as long as the voltage is relatively close to spec, it will be fine. Amperage doesn't mean anything when power supplies are rated in watts, you can never have too many, and too few won't damage anything.

 

Anytime you have to physically hold the power port to get a charge or power up the laptop is problem with the power port plug and should be inspected.

Yes, in this case Amperage does matter too little and you will overload the charger and too much risk damaging the laptop itself. So Voltage isn't the primary concern Amperage far more important for charging and keeping the laptop power correctly from damaging more then just the power port plug you risk overloading the laptop components those small parts can't only take so much before they are damaged beyond repairs.

 

That isn't how it works. The voltage remains steady, and is determined by the power adapter, but the current is variable, and is determined by the laptop, but with a hard cap on the maximum that the power supply can provide. If the power adapter can't supply enough current, the computer will either run down the battery even while plugged in, or will simply shut off. In most situations when you are charging the battery, the power adapter is supplying its maximum rated current, even though the computer could consume more. On the other end, a power supply can never be able to supply too much current. The laptop will consume as much as it wants, with the power adapter never limiting the ability of the laptop to run or charge its battery as fast as its internal circuitry will allow.

 

No that isn't how electrical system they don't follow your lead if the charger isn't able to supply the Amperage draw you will force the charger to work harder to supply the need Amperage and that will shorten or short circuit the charger itself causing it to heat up and cause fires eventually leading to hardware failures. Why do you think manufactures tell you when you order replacement chargers they must match both Voltage and Amperage to maintain proper system integrity. This other example...a Car battery without you can run or start the car...have a failure in the Alternator and the battery is discharged causing internal cell damage and in turn causing the alternator to work harder to maintain the proper voltage and charge levels which leads to more Alternator failures and thus damaging the battery more. So as you see one problems leads to failure in the other and back and forth eventually you will kill both or one of the components. So you end up with both a bad battery because of being discharged to point it can't take a charge anymore and a Alternator worked so hard it also fails. So if Voltage and Amperage isn't maintain in the system you can expect problems to happen.

This part doesn't make sense consume more like kill your laptop would be more precise they make the charger and laptop charging circuit to match for specs to prevent such damages to laptop and charger to start with. This logic will consume more will end up burning up the board and charger. Overloading or overtaxing circuits will result in component failures. Laptop are made for exact specs not because you want it but that is what the components can handle safely before failures.

The logic isn't sound in itself...if there is a short in the system the power supply will get shorted out because the draw is to much. And no laptop don't consume as much as it wants otherwise you would burn out the board power control circuits-that makes no sense. A short in the system will overload the charges circuits anyone will know that works on electrical devices with battery and external power source resulting in electrical hardware failures.

 

Besides pointing out that you also have no idea how the electrical system in cars works, I guess you have never heard of people using different sized power supplies with their laptops? For example, my laptop came in two versions, one with integrated graphics with a 65w power supply, and one with switchable graphics with a 90w power supply. I have the one with switchable graphics, and I can use either power supply just fine. The 90w one charges the battery faster. However, if I use the 65w power supply and run the CPU at full load while using the discrete graphics, I can get the computer to shut itself off. Nothing is damaged. Conversely, my old netbook had a 45w power supply, but it would take a while to charge a dead battery if I was using the computer at the same time. I got a 65w power supply for it and it worked perfectly to speed up the charging speed. On this forum in the past I have seen lots of people who have upgraded their power adapters to ones rated higher, especially for those wanting to overclock gaming laptops.

In addition, how on earth do you expect a desktop computer's power supply to work? They don't have specific power supplies for DIY computers. You just need to get something that puts out at least XXX. If you get a power supply that is too big, it doesn't matter. You just won't use it to its full potential. If you get one that is too small, well, then your computer will shut down when you put it under load.