Re: Dell PA-12 / PA-10 laptop adapter repair / rebuild
ChipInNC
The DC power cable going to the laptop has three conductors that are
layered similar to coax or audio cables. It has a single center
conductor that is wrapped with a (middle-layer) shield and then both
conductors are then wrapped again by a final outer shield. The layers /
shields optimize the cable for minimal electrical emissions and
interferences while allowing for maximum flexibility.
The center conductor goes to the center pin on the barrel shaped laptop
connector and is used as a data line to tell the laptop what "kind" of
power supply it is.
The inner (middle) layered "shield" is actually VCC / positive (+ 19.5
volts DC) and goes to the inside edge of the barrel connector (nearest
to the center pin).
The outer most "shield" is ground and goes to the outside edge of the
barrel connector.
During the course of use (and abuse) the cables tend to get damaged and
need to be repaired or replaced. The good news is that when the cable
has a short between VCC (+19.5 volts) and ground, the adapter usually
detects the problem and shuts itself down (no power LED) on both PA-10
and PA-12s.
If the center / data connector is shorted to VCC, the adapter may still
be protected on a PA-10, but will most likely be trashed on a PA-12 due
to the lack of a protection circuit.
NOW, WITH THE UNIT OFF AND TOTALLY UNPLUGGED FROM BOTH AC AND THE
LAPTOP...
Open the clamshell as listed above, and test the conductivity between
all three conductors at the barrell connector. Ground to positive,
ground to the center pin / data connection and positive to the center
pin.
They should all be open connections between each other. If there is a
short, between two or more connections then that will be the first issue
to fix.
Take the DC power cord and cut it off from the adapter at a point that
is closest to the rubber sleeve coming out of the adapter, but past any
obvious distress / exposed wires. This is our starting point.
Take a sharp knife and carefully cut the outside insulation from the
cord about 1.5 inches down from the newly cut end. Separate the shield
from the inner layer and twist it tightly. This is the ground
conductor.
Next take the inner conductors and remove the last inch of insulation
from around that shield. Separate the middle shield from the center
conductor and twist it tightly.
Now take the knife and remove about a 1/4 inch of insulation from the
center electrode and twist it tightly.
You may tin the ends of all three conductors with solder now if you
like.
Test all three contuctors for shorts and then for full conductivity
with their repective connections on the barrel connector.
If you found shorts or open connections, move up the line about 6
inches (or past wherever you suspect there is damage to the cable) and
re-do all the above. Continue until there are no shorts and full
conductivity to the connections on the barrel.
Keep in mind that you are also looking for intermittiant shorts / opens
as well.
** You may end up running out of wire and have to get a new cord **
If you do end up needing a new DC power cord, here's a vendor for them
($15 each though):
Let me know if anyone finds a better / cheaper source for these!
ChipInNC
We started this discussion in another thread, but looking at it I
thought it would be better served in a new thread.
Many people have problematic or dead Dell PA-12 or PA-10 series laptop
power adapters that they'd like to fix but don't know how to.
First a BIG disclaimer!
*** IT VERY EASY TO GET SHOCKED AND MAYBE KILLED WORKING ON THESE.***
*** DON'T EVER PLUG IN THE AC CORD WHILE THE CLAMSHELL IS OPEN OR ANY
PART OF THE UNIT IS EXPOSED!!! ***
*** DON'T WORK ON THESE IF YOU ARE NOT TOTALLY FAMILIAR WITH
ELECTRONICS AND SWITCHING POWER SUPPLIES! ***
*** THERE'S A LOT MORE THAN THE 20 VOLTS DC TO DEAL WITH AND YOU COULD
DIE! ***
Keep in mind that although I have fixed over 100 of these, it probably
took opening and working on about 150 of them to get the 100 fixed ones.
PA-10 are usually more easily fixed than the PA-12s. There's lots of
reasons why, but the things I've found that favor the PA-10s are easier
opening of the clamshells and and some electronic protections (resistor
/ diode) in the center-pin / data line circuit that protect the DS2501
(the three legged transistor looking device near the DC output
connections) from over voltage spikes. There can happen when the center
pin of the barrel connector touches or otherwise connects with the
inside of the barrel connector (+19.5 volts DC).
The DS2501 sends data to the laptop "describing" the AC power adapter
attached. It needs to function properly to use the adapter on a Dell
Laptop or docking station / port replicator. Otherwise it may not
charge the battery or even work at all.
To "fix" one of these adapters, you need to find out what the issues
are. It's usuallay an open or short on one or more conductors on the DC
power cord. (possibly intermittant)
To test the adapter, first remove the barrel connector from the laptop.
Then plug the adapter into an AC outlet and observe the LED indicator.
A lighted LED indicator usually means you have good DC voltage present
inside the adapter.
If the LED was on, check to see if there is 19.5 volts at the barrel
connector. Take your ground from the outside edge of the barrel
connector and take your positive from the inside edge of the barrel. Be
vary careful not to allow you probe to cause a connection between the
inside of the barrel (Vcc) and the center pin (data) connector.
If the LED was on and there was voltage present, then most likely the
inside data line conductor is open or possibly the data
"chip/transistor" has been fried.
If the LED was on and there is no voltage present, then most likely the
positive or ground connection is open.
If the LED was off, there should be no voltage and probably (hopefully)
the positive and ground connections are shorted and the unit turned
itself off before any damage occoured.
You may have intermittiant connections that come and go as well.
Write down or remember the initial state of the adapter for additional
troubleshooting steps later.
OPENING THE ADAPTER:
The first step in fixing one of these adapters is to open the adapter's
clamshell case.
Let me tell you, I've looked all over for a video to help describe this
process, but couldn't find one. That's why there's such long
descriptions here.
Here's the best description I can give. First, you need to find the
right sized flat bladed screwdriver to help you open these. It needs to
be thin enough to get between the cracks but also wide enough in the
other dimension to maximize the force on the PA-10/PA-12 clamshell when
turned/twisted.
I have a Victorinox "Swiss Army" knife that I love to use for this.
Either a "One-Hand Trekker Black Blade" or "Soldier Knife 08" are the
best. The main reason is that they have a locking screwdriver blade
(thin, but 7mm wide) and a locking serrated knife blade. The locked
blades means they are safer to use as it won't fold up on you, mid use,
causing problems or injury.
Take the adapter off the computer and remove the AC cord (two prong or
three prong) from the unit. You now have the clamshell that contains the
transformers and electronics of the power supply, and the DC power cord
that delivers the 19.5 Volts DC (and data line) to your laptop.
Next, I take the wide, locking, 7mm flat screwdriver blade and insert
it between the clamshell and the AC power socket (2 prong or three
prong), close to each outer edge of the socket, and twist the
screwdriver blade clockwise and counter-clockwise to try and get the
clamshell to "pop" on either or both sides.
If that area is stuck, I put the blade in the side of the clamshell
where the rubber strap goes and twist there as well. I don't push the
screwdriver into the clamshell here as there is usually a large
capacitor just behind that indentation that can get punctured if you
push it in too much. I'm really just using the blade against the "lips"
that are there for leverage in separating the clamshell.
If you're lucky, you'll get a nice clean "pop" on all of these areas
and it becomes easy to open the clamshell. If not, then you have to get
some amount of clamshell separation at one of these points to use as a
starting point for using either the knife or screwdriver blade to slowly
and carefully expand the crack along the edge.
Once you get a crack started along one of the edges, you'll notice that
the clamshell has an overbite side and an underbite side. The overbite
side hides the seam and is on the outside of the seal. The underbite
side attaches / seals to the inside of the overbite side.
Insert the screwdriver blade between the clamshell, at the crack, with
the blade laying against the side of the clamshell and the top edge of
the blade inside the clamshell under the "overbite" side. Twist the
blade to open and separate the inside and outside edges of the clamshell
seal while scooting the blade along the edge.
Keep in mind that there are components inside that can get damaged if
you just go jamming blades in randomly.
You will have to judge how hard to "push" or turn the screwdriver blade
as you go along. Some adapters are easier than others. Most PA-10s are
easier than most PA-12s. Also, most PA-12s don't have a protection diode
on the center data line, so they usually aren't as easily fixed.
Hopefully at some point you'll get to a point where you can easily
separate the clamshell halves. I usually end up popping the sides with
the AC socket and the "lips" for the rubber strap first, next opening up
the side where the DC wire comes out of the adapter. Then the "flat"
side of the clamshell can be separated by bending it back and forth at
the seam to separate the other side.
ChipInNC
Once you have the unit opened up (yes you might have cracked the
clamshell or otherwise done some cosmetic damage), take a close look at
the DC wire and what it looks like. This will be the most often damaged
part of the unit.
More disclaimers:
*** IT VERY EASY TO GET SHOCKED AND MAYBE KILLED WORKING ON THESE.***
*** DON'T EVER PLUG IN THE AC CORD WHILE THE CLAMSHELL IS OPEN OR ANY
PART OF THE UNIT IS EXPOSED!!! ***
*** DON'T WORK ON THESE IF YOU ARE NOT TOTALLY FAMILIAR WITH
ELECTRONICS AND SWITCHING POWER SUPPLIES! ***
*** THERE'S A LOT MORE THAN THE 20 VOLTS DC TO DEAL WITH AND YOU COULD
DIE! ***
On the PA-10's, I usually replace the final capacitor, usually closest
to the DC wire, with a new one (I use Panasonic FM or FC series, 470uf /
25volt, capacitors from Digi-Key). By the time you're repairing one of
these power supplies they usually have started to fail, the top is
popping up and ESR is increasing.
I'd rather spend the little bit of time and energy doing that, then
having unfiltered / under filtered power going into the laptops where it
can do much more damage.
Usually when you're opening these units, it's to repair or replace the
DC wire. If there is anything that has failed, other than the wire and
/ or final capacitor, I recommend trashing the unit and getting a new
one. It's just not worth the time and energy to fix anything else
inside. It's potentially dangerous too as there are very high voltages
inside that can hurt you, kill you or damage your laptop. Please, be
careful!!!
RnR
Personally for the $20 to $30 / brick, it wasn't worth my life, so I
just ordered 2 new ones. One of mine acted up in the past, tho lately
it's working fine. I won't trust it so I have 2 on standby (also have
another laptop of the same).