Dell Inspiron Laptop frying AC adapters

joe7dust

Laptop works fine if a fresh battery from his friends Inspiron is inserted. Laptop works fine if a brand new AC adapter is used but after 1-7 days it "shorts out" and is completely broken and does not work on his friends Inspiron. (he has gone through 3 AC adapters)

I'm considering replacing the power jack but I am hesitant because he says he didn't drop it and usually power jacks break from force not out of the blue right?

Only other thing I can think is it has a faulty motherboard but that doesn't sit with the fact that a fresh battery = works fine.

daily_2

Have you tried it without the battery in?

joe7dust

I think he has. I am supposed to be fixing it tomorrow just trying to get a head start.

What are you trying to establish with that question? I would assume you are trying to rule out the battery. Since several batteries have been used with same results, even if the answer is no I still think several different batteries are unlikely to be the cause.

Strider590

Break into the supply line somewhere from the adaptor to the laptop and check the current consumption with a multimeter..... Does it exceed that of the AC adaptor?

Have you considered outside influences? like a dodgy/unstable mains supply?
They get really warm too, is there adequate ventilation where it's used?
Some cheap SMPSU's have no "dummy load" and don't like to be left turned on with minimal load current (they can get really unstable), does he turn the PSU off when the laptop is off?

pupmaster

Just a thought is the power right ie 19v 4.5amp if you use 19v 3amp it might be straining a little.

joe7dust

@daily
If the battery is not inside nothing happens, it will not run off the adapter without a battery in it.

@pupmaster
Both the laptop bottom and power adapter say 19.5V and 3.34A, and family PA-12 adapters.

Strider590 wrote: »

Break into the supply line somewhere from the adaptor to the laptop and check the current consumption with a multimeter..... Does it exceed that of the AC adaptor?

What is the least destructive way to do this? From the videos and how-tos I've read in order to measure current I have to "break" into the circuit which would mean cutting the cord between the power "brick" and the laptop. I don't want to give this guy his power adapter back with a kink in the cord and electrical tape, etc.

Strider590 wrote: »

Does he turn the PSU off when the laptop is off?

No, he usually leaves it plugged into the wall even when not in use.

Strider590

joe7dust wrote: »

What is the least destructive way to do this? From the videos and how-tos I've read in order to measure current I have to "break" into the circuit which would mean cutting the cord between the power "brick" and the laptop. I don't want to give this guy his power adapter back with a kink in the cord and electrical tape, etc.

No, he usually leaves it plugged into the wall even when not in use.

I would be inclined to find an adaptor plug of the same fitment, youve got other damaged ones haven't you? cut the wires making note of the polarity.
Plug that into the laptop with two stripped wires hanging freely, wrap the wire around the outside of the plug on the good adaptor (remember polarity) and place a multimeter between the other wire and the centre of the good adaptor plug. (the meter probe should fit). Or you could do it the other way around and push the other wire into the end of the plug.
Hope that makes sense? you'll avoid damaging the good adaptor that way.

Tell him not to leave the adaptor plugged in when the laptop is not in use, it's not a good thing to do, they don't really like it because once the battery has fully charged there's almost no load present. I've got a laptop adaptor that actually makes a screaming noise when left on with the laptop turned off, if I left it on it would definitely kill itself eventually, im 100% convinced of that.

joe7dust

Thanks for that, I think I understand. Just one more question about it. I was expecting 2 wires but there are 3, 1 unshielded 2 shielded. My guess is the white wire = (-), red wire = (+) and the unshielded is ground? If that is the case I can just ignore the unshielded one then?

Strider590

If that's the case, and I have to admit ive not come across that! but I know Dell use 3 pin connectors on some of their laptop range. You should take voltage measurements from pin to pin.

You are looking at the laptop side of the PSU right?
From your description you'd get +V and -V with reference to the ground and double that voltage across the + and - lines.
Laptop PSU's typically generate between +16v and +19v.

On a side note, you have brought genuine Dell PSU's haven't you? A friend of mine just informed me that after market PSU's for Dell's seem to have a high mortality rate.

joe7dust

Strider590 wrote: »

If that's the case, and I have to admit ive not come across that! but I know Dell use 3 pin connectors on some of their laptop range. You should take voltage measurements from pin to pin.

You are looking at the laptop side of the PSU right?
From your description you'd get +V and -V with reference to the ground and double that voltage across the + and - lines.
Laptop PSU's typically generate between +16v and +19v.

On a side note, you have brought genuine Dell PSU's haven't you? A friend of mine just informed me that after market PSU's for Dell's seem to have a high mortality rate.

Yes it's genuine, he got them under warranty but now it's not in warranty. Yes it's the laptop side. I actually haven't had to use a multimeter in a very long time, so I need to brush up on some how-tos before I even start measuring the lines. Just tell me if there is something I really want to avoid that could cause a short or damage my multimeter.

Strider590

joe7dust wrote: »

Yes it's genuine, he got them under warranty but now it's not in warranty. Yes it's the laptop side. I actually haven't had to use a multimeter in a very long time, so I need to brush up on some how-tos before I even start measuring the lines. Just tell me if there is something I really want to avoid that could cause a short or damage my multimeter.

Yeah make sure you don't have the leads on the meter connected for current measurement when your measuring voltage else you'll short the PSU.