No Power or Battery Charge on Laptop - Power Jack seems OK

[BlayneRTFM]

I had a client recently bring in a Dell Inspiron 9400 Laptop that he said was no longer charging the battery. The first thing I did was test the Targus charger which the client had just bought to replace the original. It was then that I noticed in testing it that it was showing -19.5 volts. After looking at it more closely, I saw that someone had put the removable tip on backwards. I tried another charger on the laptop and I cannot power on the laptop or charge the battery at all. I tried removing the external battery and cmos battery and holding the power button for 60 seconds to discharge the laptop and plugged the adapter back in - still nothing. I tested the posts connecting the power jack to the motherboard and it is getting sufficient power. So I am assuming the power jack is fine.

I am thinking that the client plugged the ac adapter in the laptop with the power tip on backwards and fried a transformer or charging circuit or some other diode or component somewhere. However, I have also read in several forums that the Inspiron 9400 is notorious for not being usable with generic ac adapters. That is, the data line in the jack tells the laptop that it is not a Dell ac adapter and won't work properly. However, it was my understanding that older Dells with the Data line check only made the generic adapter unable to charge the battery but supplied sufficient power to run the laptop otherwise.

Can anyone clarify this for me? Is plugging in the ac adapter once with the tip on backwards sufficient to fry components on the board or would the adapters protection mode not kick in and prevent damage? And would a generic charger have issues with older Dells like the 9400 or do new adapters have a built in workaround for this issue?

Thanks.

 

[BlayneRTFM]

Can't seem to edit my own post? Forgot to add that the laptop works fine on battery. Just can't run on external power only or charge the battery.

 

[ChrisHirst]

Sounds like the PSU has died and cannot deliver enough current. Test meters are very high resistance do do not put any load on the circuit or the device being tested.

Chris.

Indifference will be the downfall of mankind, but who cares?
Time flies like an arrow, however, fruit flies like a banana.
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[rclarke250]

Well, the Transformer is in the Targus power supply, And it would not be damaged by flipping the tip around, it could care less, as it sits on the AC side of the circuit. Now that being said, it is more likely that the regulators and diodes of the charging circuit were damaged if they did indeed plug it in with the polarity reversed. As it most certainly supplied enough voltage to go past the breakdown voltage and the diodes and p-n junctions of the regulators were destroyed. This is on the motherboard, and if you want to and can replace components on the board, more power to you, good luck finding the schematic. As the machine is 6-7 years old, it is not worth putting any money into it, as for under $300.00 usd you could get a brand new machine with better specs.

 

[ChrisHirst]

But for for under $10

http://www.amazon.com/Replacement-L...HV4M/ref=sr_1_1?ie=UTF8&qid=1395015478&sr=8-1

Chris.

Indifference will be the downfall of mankind, but who cares?
Time flies like an arrow, however, fruit flies like a banana.
Webmaster Forum

 

[BlayneRTFM]

Thanks for the replies. I figured the mainboard was done. Trying to hunt down all the components that are fried and replacing them would be far too much trouble and a replacement board is $150.00 + shipping. Add the cost of labor and it's clearly not worth it. Already told the client they'd be better off getting another laptop - preferably not a Dell. Hate telling people their item is not worth fixing but - what can you do? It's 7 years old and has XP. I figure they've gotten their money's worth out of it. The only reason they still use it is to run an old program for their business. I'll have to teach him how to use windows xp mode on a new laptop.

Thanks for the help.

 

[rclarke250]

Chris, that is great, but it's not the power supply. It's the charging circuit on the motherboard that is most likely damaged. Also Blayne, with a 2 pin power adapter, there is no such thing as a data line. It is a positive voltage, and ground, that is it. Try another adapter either another dell or 3rd party.

 

[BlayneRTFM]

Thanks. I've already tried 3 adapters all with the same result. No power to the laptop or the battery. I have dozens of adapters but, no Dell's at the moment.

From what I understand and have seen with some old Dell's, some do have a 3 line adapter. A positive, a ground and a data line that connects to a chip inside the adapter. If you cut the line on some older Dell's, and crack open the adapter, you can see the 3 wires. One wire, leads to a small chip in the adapter on one end and to the center pin on the male end. Some people have actually removed the chip from the Dell adapter and soldered it to the center pin post on the motherboard creating a permanent connection with the chip allowing the ability to use any adapter. As I don't have the original adapter, I have no way of knowing if this model uses the same "feature".

The Targus adapter that the client purchased was charging the battery just fine for a few days before the client accidently disconnected the tip and put it back on in reverse. So, I am assuming either this one doesn't require an original Dell adapter with that chip or the motherboard was flashed with a newer BIOS that removed the requirement. I have no way of checking the current BIOS version as the laptop battery is now drained.

I'm pretty sure the charging circuit is toast - probably other components as well. I've checked the female ac jack on the motherboard and all posts have a good connection to the board and receiving a charge from the adapter so, the only possibility I can think of is a bad component on the main PCB.

Thanks.