Possible solutions for burnt-out circuitry on Dell Latitude D505 mobo?

[logand]

Recently my Dell Latitude D505 quit powering off of the AC adaptor or charging the battery while plugged in. It still runs fine on battery. I've ruled out an AC adaptor problem, and an in-depth (read: take laptop to pieces) examination seemed to indicate that there was nothing wrong with the AC adaptor-to-motherboard connection. Best guess is at this point that a power surge knocked out some of the circuitry on the mobo (there was a storm on the night the problem started, and the laptop was plugged in), a problem that would cost around $500 to fix with a Dell-supplied part. Therefore I am looking at other ways that I could continue to use this laptop.

Most probably I considered getting several laptop batteries + an external battery charger. Does anyone know of a good place to get an external battery charger?

Secondly, does anyone know if it might be possible to somehow hack a solution so that I could power the laptop with AC through the battery power connections, which seem to bypass the affected circuitry. Has anyone ever done this before? People on this board have discussed over-hauling laptop batteries using replacement cells, couldn't theoretically someone simply power the connectors in the battery with the equivalent current? I'm really a newbe at these hardware issues, so help would be appreciated.

[elroy]

Proceed at your own risk !!!
If the AC power supply puts out the same voltage as the batteries I would solder the wires from the AC adapter to the battery terminals inside the lappy. Then you would have a permanently attached power supply.
If you want to go with the mulitple batteries and an external charger I would look on Ebay for a charger.

[d505]

Hi, I opened the battery and took out the cells. soldered the wire from a 12V AC adapter directly to the battery connecter. Then put the empty battery (only has the connecter/circuit board and the ac wires) back to the laptop. Mulitmeter reads 12.58v that is similar to the battery's reading 12.0v. However, the laptop does not turn on at all. Does anyone knows what's the problem/

Quote:

Originally Posted by logand

Recently my Dell Latitude D505 quit powering off of the AC adaptor or charging the battery while plugged in. It still runs fine on battery. I've ruled out an AC adaptor problem, and an in-depth (read: take laptop to pieces) examination seemed to indicate that there was nothing wrong with the AC adaptor-to-motherboard connection. Best guess is at this point that a power surge knocked out some of the circuitry on the mobo (there was a storm on the night the problem started, and the laptop was plugged in), a problem that would cost around $500 to fix with a Dell-supplied part. Therefore I am looking at other ways that I could continue to use this laptop.

Most probably I considered getting several laptop batteries + an external battery charger. Does anyone know of a good place to get an external battery charger?

Secondly, does anyone know if it might be possible to somehow hack a solution so that I could power the laptop with AC through the battery power connections, which seem to bypass the affected circuitry. Has anyone ever done this before? People on this board have discussed over-hauling laptop batteries using replacement cells, couldn't theoretically someone simply power the connectors in the battery with the equivalent current? I'm really a newbe at these hardware issues, so help would be appreciated.

[nubber]

Quote:

Originally Posted by d505

Hi, I opened the battery and took out the cells. soldered the wire from a 12V AC adapter directly to the battery connecter. Then put the empty battery (only has the connecter/circuit board and the ac wires) back to the laptop. Mulitmeter reads 12.58v that is similar to the battery's reading 12.0v. However, the laptop does not turn on at all. Does anyone knows what's the problem/

I was thinking about trying the same thing. Does anyone know if a AC/DC to battery terminal approach is possible. It sounds like a fairly sensible fix. I just don't know if the voltage will be the same. Any thoughts?

-James

[Nuser]

Yup, I got the same problem. Tried to connect a DC supply from the battery connectors but it didn't work. The pc I'm using just blinked for a second and shut off.

Some info I gathered from other forums (EeeUser ASUS Eee PC Forum / Running EEE w/ a power supply connected to the battery terminals.)
suggests that the laptop "reads" data from the batteries and determines their states and shuts off when the requiered response (from the batteries) does not come. Still thinking of ways to overcome this ...else got a brick that won't charge the battery and won't work on AC.

Somebody else have anymore ideas?

[Nuser]

Yup, I got the same problem. Tried to connect a DC supply from the battery connectors but it didn't work. The pc I'm using just blinked for a second and shut off.

Some info I gathered from other forums (EeeUser ASUS Eee PC Forum / Running EEE w/ a power supply connected to the battery terminals.)
suggests that the laptop "reads" data from the batteries and determines their states and shuts off when the requiered response (from the batteries) does not come. Still thinking of ways to overcome this ...else got a brick that won't charge the battery and won't work on AC.

Somebody else have anymore ideas?

[brimar]

Quote:

Originally Posted by Nuser

Yup, I got the same problem. Tried to connect a DC supply from the battery connectors but it didn't work. The pc I'm using just blinked for a second and shut off.

Some info I gathered from other forums (EeeUser ASUS Eee PC Forum / Running EEE w/ a power supply connected to the battery terminals.)
suggests that the laptop "reads" data from the batteries and determines their states and shuts off when the requiered response (from the batteries) does not come. Still thinking of ways to overcome this ...else got a brick that won't charge the battery and won't work on AC.

Somebody else have anymore ideas?

Just repaired a laptop with the same symptoms:
Won't charge the battery, won't power from AC.
Also if you power the AC adapter when not connected to laptop you get green power LED on the adapter. When you plug it in the laptop the green power LED immediately goes out.

Opened it up and found SO-8 P-ch mosfet by the DC input socket. Source (pins1,2,3) is connected to the inner barrel (+19.5V), Gate 4 gets driven low, applying the input to the Drain. (pins 5,6,7,8) On my board the drain was short to GND. Applying power directly to the Drain via a current limited bench PSU (set 1A limit) showed a couple of volts.

Placing a finger on the opposite side of the board revealed a SMT ceramic cap getting hot.
CP13 I think. Opposite side to the power connector, almost under it. I would guess at 1206 or slightly larger and there is an 0402 cap just next to its bottom pad at 90 degrees to it. Cap was glued before soldering so had to flow both sides at the same time with a soldering iron and force off. Would likely have been 1uF or bigger 25V. Removal restored operation. Runs OK without but would suggest putting something in there 0.1uF 1206 50V, perhaps a couple stacked ?

BTW you have to strip down everything and remove the main board to get to the cap :-(

Hope this info is of use to someone....

(EDIT) correction: cap is PC13. Pic showing location of failed cap - D505fix

Robin
die4laser.com

[Bomans]

Hi,

Was the laptop that you repaired also a dell latitude?
Because I don’t understand which component you removed . So if it was the same laptop type, maybe I can post some pictures of the circuit board and than you can indicate which component you removed?

Thx

[brimar]

Yes, it was a D505.


To get at the capacitor you have to follow the full teardown given on the Dell website as service info for the D505.
Documentation

If you can send me a photo of the underside of the board in the area of the power connector I might be able to point out the one I had fail.
There is some metalwork which obscures the underside of the power connector. I ended up hacking this away with a pair of side cutters whilst trying to trace through the input circuit. I think when I found the cap I realised that I could have got away without doing the hacking. Try a couple of photos from different angles so if the cap was just under the metalwork I could still see it.

The cap is a fairly large ceramic - on the underside of the board and on its own with the exception of a MUCH smaller ceramic one by one of its pads but the smaller one is rotated 90 degrees to it.
I think all the other large ceramic capacitors in this area are grouped together.

You might be able to see some signs of damage to the cap.
when these fail they can crack. The cracks appear as a lighter cream line in the ceramic body of the cap.

[ShineOn]

brimar,

I also have the same issue - my D505 works off battery but battery won't charge, and if you plug in the PS the light on the brick goes out. I have my mobo in front of me and see the mosfet you're talking about (PQ12 is silkscreened next to it).

Not sure where the ceramic cap might be on the underside. You mention CP13, but all the power-related components on my mobo appear to have a P before the component type (PC, PQ, PR, PD, etc.) I found a PC13 in line with the PV3 flexible contact on the underside next to where the power connector is mounted. Hard to tell from visual inspection if it's bad.

I suppose it could be any of the caps in the power circuit, though...

How did you connect your low-output PS at your test-bench, and could the resistance test setting of a multitester work as a low-output PS for the purpose of heating up the defective cap?

(edit) Never mind - I found that cap has a dead short across it using my multimeter's continuity test. Replaced it with one the exact size & shape I snagged from a bad Inspiron 5100 mobo... I'll post back with the results.

(edit) That did the trick! You're a genius! This little "secret" has GOT to be shouted from the rooftops.

That just goes to show you that a dead component doesn't have to have any visible signs of damage.