Dell Inspiron Laptop frying AC adapters

joe7dust

God this sucks... There used to be a green light on the power brick, but now it's not there at all.

I went ahead and tested it anyway. I'm using a Cen-Tech digital multimeter with black cable plugged into COM and red cable in V(Ohm)mA. The dial is set to 200 ACV. Putting the red lead on the unshielded and black lead on the white gives about 0.4 and with red lead on the white cable and black lead on the red cable it can go as high as 0.6 but there doesn't seem to be a real solid contact so it varies.

I'm thinking that I need to connect the unshielded to either the red or white because they connect at the laptop plug and its some sort of fail safe mechanism. Basically it knows I cut the cord somehow so it's not turning on.

Strider590

Hard to say without having it in front of me.
If the 2 pins are shorted on the laptop side try that, I cant see why they would be though.

Oh and set your meter to DC voltage though else you'll get nothing useful.

joe7dust

OK got some data for you, what does this mean? Multimeter dialed to the DC section, more specifically "20" between "2000 M" and "200"

Red to Unshielded = 0.06
Red to White = 12.5
White to Unshielded = 19.75

About my last post I guess that was just a fluke or maybe because I had it plugged into a strip with a lot of other things.

Strider590

Sounds like white is the supply, red is apparently used to detect whether the PSU is genuine Dell and to detect the current capacity of the supply. The final pin is GND. Dell make two different inspiron supplies, one is a 65W the other is a 90W, but they are autodetected by the laptop which kinda blows the over current theory out of the water unless there's a problem with the detection circuit.

Something on the laptop is causing the PSU to operate outside its intended parameters, an intermittent power connector could cause perhaps transient voltage spikes causing the PSU to have to constantly adjust its output voltage more than it normally would, especially during battery charging. I just can't imagine it myself, it's almost like an extreme possibility.
But from a fault finding pov, the golden rule is never to over look anything no matter how obvious or unlikely and no matter who says they've done what or checked what.
Give that connector the once over, even if it looks ok, resolder it anyway. Check the surrounding components (soldering) while your there.

joe7dust

65W detected in BIOS

Current being drawn on the white wire = 3A
" " red wire = 0A
" " bare wire = 3A

This doesn't quite match up with what it says on the power supply. (3.34A)

Something else I noticed is that when I complete the circuit it says "idle" and the current = 0.9A then a few seconds later it switchs to "charging" and then its 3A. About 10 seconds later it goes back down to 0.9A yet still says "charging" then about 3 seconds later switches back up to 3A and appears to hold there. (I monitored it for about 1 minutes)

I think perhaps my connections weren't that great because when I try to test the current on the red wire it goes to an error message about non-genuine Dell power supply detected. I should probably twist the wires around the leads and tape them. For these tests I was just pushing down on the wires with the leads.

Maybe I should try loading windows and see if the current changes. I just had an idea for a virus that could switch it from idle to current over and over taxing the power supply.

joe7dust

When the laptop is off it is only drawing 2.46A which is a lot less than what it says on the "brick" part (3.34A)

The connections were fine btw, tape didn't change readings at all.

I may have identified the problem, seems the connection between the wall plug and the "brick" has to be nearly perfect. I couldn't get the light on the "brick" to come on so I just unplugged this connection, examined it and reconnected very firmly and it came back on.

I'm thinking that either he considered the other 3 adapters to be broken when it just needed to be reconnected like this, or they broke because of stress brought on by a loose/intermittent connection here.

Another more complicated possibility is that there is another unknown intermittent problem and what I noticed here was a coincidence and sign that this adapter is soon to join it's broken cousins.

I hope its not the last theory...

Strider590

joe7dust wrote: »

Something else I noticed is that when I complete the circuit it says "idle" and the current = 0.9A then a few seconds later it switchs to "charging" and then its 3A. About 10 seconds later it goes back down to 0.9A yet still says "charging" then about 3 seconds later switches back up to 3A and appears to hold there. (I monitored it for about 1 minutes)

I'd expect this behaviour, it's a charger/battery test prior to starting full charge. If the battery accepts the short duration charge and then holds voltage it'll assume all is ok and continue charging. SLA battery mantainence chargers do the same thing over a longer period of time.

So far i've only seen one reference anywhere to Inspiron PSU failures, this was regarding the 1100, 1150, 5150 and 5160 model's.

Mentioned was the DC socket on the laptop, then your intermittent mains power connection and also a few reports of wires going open circuit at the DC side at the laptop..

The later I assume is from the manual removal/replacment of the power lead when going mobile with the laptop, or picking up the laptop with it plugged in and stressing the cable (those bricks do weight a fair bit). I get through mobile phone chargers the same way! Luckily my laptops (1 for work 1 for my HTTP/FTP servers) both have docking stations.

Does the plug have a ferrite core/block next to it? was that being used to pull the lead out of the laptop? damn silly question I know!

joe7dust

Yes there is a cyclinder near the laptop plug, but I don't know if that was being pulled on. I would assume no, but I'll ask tomorrow. It is an Inspiron 1525 by the way.

"Mentioned was the DC socket on the laptop, then your intermittent mains power connection and also a few reports of wires going open circuit at the DC side at the laptop..

The later I assume is from the manual removal/replacment of the power lead when going mobile with the laptop, or picking up the laptop with it plugged in and stressing the cable (those bricks do weight a fair bit). I get through mobile phone chargers the same way! Luckily my laptops (1 for work 1 for my HTTP/FTP servers) both have docking stations."

You pretty much lost me after 'DC socket on the laptop'. I guess I should mention I'm never really deal with electrical issues like this. Usually I would just buy a higher wattage power supply or find a better electrical outlet to use.

What do you make of the lower than expected amperage?

Strider590

Oh I see what you mean, sorry I have this habbit of assuming people know what im thinking, I should have noticed and responded, but my head ran off into tech land.
It's just like.... I can handle two conversations on two PC's at the same time with the left hand on one keyboard and the right hand on the laptop keyboard.... I often get annoyed (very wrongly) when im communicating with people who can't and I have to slow down what im doing to accomodate. I really must work on that! lol

Anyway, back to the point.
I think basically it's operating normally, it should never reach the maximum capacity of the supply, in fact i'd be more worried if it did. An overloading switch mode power supply is never a pretty sight.

Im sure the PSU's can be picked up on ebay for a bargain price, I would be inclined to suggest that your friend really looks after this one, taking care to remove the power connector carefully and siwtches off at the mains when its not in use, which is better for the L-ion battery anyway.
If it goes again with all the possible care being taken then you'll know for sure that the problem lies within the laptop itself.

joe7dust

I decided to drain the battery to 0% and try charging it to see how it does. It kept waivering between 0.00A to 0.80A (mainly 0.70Aish) with occasional spikes to 1.00A and 2.30A.

I noticed the light on the brick was glowing bright, then medium then fading out a bit and back and forth. It seemed to get better after wiggling the connection between the brick and the cable that leads to the electrical outlet.

If I didn't know the backstory involves 3 separate adapters I would think this is a problem with the adapter. If that is the case it would have to be a design flaw and then you'd probably have found something about it when you found that other stuff.

Finally after much disconnecting and reconnecting of this part I was able to get it to stabalize at 2.3A and it has held for 10 minutes so far.