Power
Adapter Cable Repair
The following represents the edited opinions of several individuals. General thanks to owners of PowerBook 2400 computers and members of the DuoList. Special thanks to Gregory, Ralph, Mark, Marc, Jack, Mad Dog, David and Jani. Keep ideas coming - photos, edits to the text, other shortcuts, materials suggestions, methods. Anyone had a cable fray at the opposite end - beside the plug to the 2400? Any other repairs done to 2400 power supplies? (Note: we still need a good image for the last frame if anyone has done a good job at reassembling the case).
- Gregory La Vardera Architect www.lamidesign.com
- Marc Blessington, Researcher www.martlet-online.com
Problem: The cable of the 2400's standard issue power supply has a known weakness near the point at which it meets the rubber strain relief protruding from the power adapter's case. Over time, stresses due to the differing flexibilities of the cable and strain relief cause an internal or external break in the cable.
Symptoms: Due to the nature of the cable's construction and severity of the damage, several different symptoms can occur. In some cases a flickering of the screen will be the first sign of trouble. (The flickering is due to different Screen Brightness settings for AC and Battery in the Energy Saver Control Panel.) This will get progressively worse with use, until finally no current reaches the PowerBook. In other cases, a visible tear develops in the outer insulation of the cable, which similarly deteriorates until one of the conductors within fails or the cable snaps off.
Solution: With the 2400's standard power adapter now officially EOL (End of Life), the only options are to either replace the adapter with a second-hand or alternative unit, or to repair the cable. The following article is a step-by-step list of instructions on how to attempt the repair.
Please note carefully: Neither the authors nor hosts of this article accept any responsibility for injury or death of anyone due to an attempt at such a repair, nor damage to their's or anyone else's property or equipment. This is merely a description of the work undertaken by others, and should not be considered an authoritative document in any sense of the word. Attempting this repair will expose people to electrical and chemical dangers, and sharp instruments.
Suggested tools: For a quite functional repair you will only need: a sharp knife, a sharp drill bit of slightly smaller diameter than the cable, and a roll of electricians tape. See also "Additional Suggestions" at the end of this page regarding the use of heat-shrink tubing or volcano tape for cable reinforcement, and "Case Sealing" regarding ABS plastic cement.
You should allow yourself about one hour, though the repair will likely take less time than that.
Enjoy.
The
Damage:
Depending on how close the damaged part of the cable is to the strain relief, there are two ways to go about a repair - repair (splice) the cable externally, or internally after opening the case.
The most common cable failure occurs as shown, right next to the rubber strain relief. No option here to splice externally.
The following instructions assume this is your case and describe a splice inside the case.
Note: If you are just attempting an external splice, sections 8, 9, and 10 may be useful in understanding the construction of the cable itself.
First step is open the power supply case.
The joint is a tongue and groove that appears to be solvent welded. The two halves can not be prized apart, they will need to be cut.
Cut the case at the visible joint that runs around the mid line of the sides, intersecting the strain relief and the power socket. The plastic is up to 3/16" thick in places so it will take a while to get through it. Getting the case open is a matter of many slow passes with a blade or the point of a blade. This is probably the hardest and slowest part of the whole procedure.
Important Note: Be warned, the more material you remove cutting the case open, the harder it will be to glue the two haves back together. Remove too much material and it will become impossible to do so.
Watch your fingers. Using some sort of clamp to hold the case might be a good idea. Be careful also not to damage either the strain relief or the two-pin power socket on the opposite side.
- "Take your time, as the guts are packed in tightly and
sit very close to the casing."
"I started with a drywall knife and new blade. After half an hour I had an idea of the thickness and I knew I did not have time to complete cutting this way. I used a dremel with a very narrow cutting blade. I'm not going to recommend this because even using a very narrow cutting blade, it removes too much material, leaving too wide a gap when you get it all back together - but it is much faster."
- "Take your time, as the guts are packed in tightly and
sit very close to the casing."
The open case.
The internal electronic block is now visible.
Note: On the under side of this block, there is an unprotected circuit board. This is a good time to take anti-static precautions.
Note also how the rubber strain relief slots into a square opening in each half of the case.
Lift out both the electronic block and strain relief from the case. These are both just held in by friction and come out quite easily.
The cable splits to the circuit board.
You can now see the two leads from the cable connecting to the circut board.
- "...and those are all the helpful directions from the list on the right!"
Note: There is in fact a third option in this repair not undertaken here. Rather than splice the cable, those more adept with a soldering iron, may prefer to solder the healthy cable ends directly back to the circuit board. Though a cleaner repair, it does carry with it increased risk of damaging the electronic components nearby. If you do attempt the soldering, make careful note now as to where each wire was originally connected to the board. Write it down.
The white wire is the core conductor, that originally ran through the center of the cable. The other, the black lead (green arrow), contains the braided conductor that used to surround the white wire, which here has been separated off and insulated with heat-shrink. Where the two conductors separate, there is a larger diam. heat-shrink (red arrow). I point this out because you will have to do something similar later to again cover this transition.
Time to cut the cable.
It seems unlikely that you'll pull any cable through and out of the strain relief - the two being either welded or just a very tight fit. (Do not try pulling too hard on the cable - you'll risk further damaging what's left!) You'll therefore need to cut the cable on both sides of the strain relief.
On the interior (case) side cut the wire as close as possible to the strain relief so as to have as much wire as possible to work with still connected to the electronics.
On the other side, again cut the wire as close as possible to the strain relief so as to preserve as much of the length as possible, but remove the damaged part of the cable.
Then, in preparation for the splice, also remove a portion of the heat-shrink insulation from the divided braided wire (red arrow).
Clean out of the strain relief.
You will need to pass the healthy cable back through the strain relief. So use a sharp drill bit, a little smaller than the diam of the cable, to clear out all the remains of the cable from the center of it - it is quite a bit softer than the rubber of the strain relief and should come out in the end.
- "When it is clear you should be able to see the
drill-bit inside the little grooves (arrows). I also tried
picking at it with a pin first, but this seemed to work
better."
"I used a very small screwdriver, about the same diameter as the cable, and by twisting and tearing, removed the remainder of the cable from the inside (it should come out in nearly one piece)."
"The long nose pliers in the photograph were useful to grip the drill-bit while I twisted the strain relief."
Another option is to entirely replace the strain relief with a length of something possibly more flexible...
- "I used a bit of auto vacuum line to replace the plastic piece that secures the cord coming out of the adapter (square hole compresses and holds the round line.)"
- "When it is clear you should be able to see the
drill-bit inside the little grooves (arrows). I also tried
picking at it with a pin first, but this seemed to work
better."
Pull Cable Back Through Strain Relief
Looks so easy - but don't be fooled.
- "Twisting helped at first, but as friction increased, it
would go no further. I had left an extension of the center
conductor to pull on - any damage the pliers do to the end
of the wire can be cut off. Once it does comes through,
though snug, it will move without too much strain."
"I used a razor blade to cut the (new) end of the power cable at a sharp angle, forming a point, before pushing it back through."
Leave plenty of slack for the splices and for tying a knot. The knot will sit against the strain relief and avoids any pulling on the cable being transferred to where it is soldered to the board. You can always adjust the position of the knot later...
- "Although tight in the case, I did manage to stuff quite a bit of wire in there."
There is a little hollow on that side of the strain relief that you can later push the knot into.
- "Twisting helped at first, but as friction increased, it
would go no further. I had left an extension of the center
conductor to pull on - any damage the pliers do to the end
of the wire can be cut off. Once it does comes through,
though snug, it will move without too much strain."
Preparing the Splice, Decisions
You now need to prepare the various elements for splicing, by separating the central core conductor (white wire) from the woven conductor that surrounds it.
There are several ways to achieve this. The most elegant option is unfortunately also the most time consuming and fidgety. The simplest is described in the accompanying photographs. The middle option lies, well, between the two.
Whichever method you choose, the aim is to have a bit less than 3-5cm of each of the two conductors (inch to inch and a half) protruding from the end of the cable. A "Y" shape, (see photo of section 10)
Simplest: Remove a section of the outer insulation (arrow) from the end of the main cable. Then as described in the following section, undo the weave, and seperate the white wire to the side.
Hardest: Achieve the same thing as above but without removing the insulation, by making a small careful cut lengthways in the cable and gently work the white wire out through the cut from between the weave with a pointed instrument.
- "Like pushing you arm through a hole in the elbow of your sweater - sleeve to one side, arm to the other"
Middle Option: Remove the length of insulation, but then ease the wire out through the side of the weave as in the above method.
Preparing the Splice, Part 2
Having removed the insulation as per the first option above, you now have to separate out the white wire.
- "I used a push pin to "comb" out the braid."
Start at the cut end and work back up towards the black insulation. "Comb" the strands of the weave to one side and the white wire to the other.
The foil shield that lies between the weave and the white wire, can either just be trimmed off when you've finished or be left amongst the strands of the weave.
Preparing the Splice, Part 3
With the two conductors separated, twist all the loose strands together to form a second "wire", something you can splice to easily.
Again, your aim now is to have a bit less than 3-5cm of each of the two conductors (inch to inch and a half) protruding from the end of the cable.
Note: Those choosing to solder directly back to the circuit board will need to proceed on their own. Pretty straight forward stuff apart from the dangers of excessive heat on the electronics. Confirm again where each wire connects.Bare, prep and tin the ends, clear the holes, and solder on. One suggestion...
- "I found it far simpler to cut the braid back leaving only 1/4 of an inch, far less to push right into the hole and solder. This way there was no need to add any insulation."
Splicing the Braided Conductor
Some planning is worthwhile at this point. Keep in mind that you will have to fit all this wiring into a small space (see photo of section 3) behind the strain relief. Too great a length of wiring and it won't all fit.
Also keep the knot loose at this point (green arrow) - you will want to move it up close to the splice shortly.
- "I considered doing an "inline" splice but then it seemed like this "twisted" splice would allow the wires to double-back and fit in better."
Splice the (formerly) braided wires together (red arrow). Twist them together right up next to the black insulation of the cable. Tinning them lightly with solder helps hold them together.
- "Note the grey work surface? Concrete doesn't burn when soldering."
Splicing the White Wire
Again, plan ahead. You can start to see how this whole thing will fold up on itself. The red arrows show how the two splices will be brought down. Don't form the two splices too close together on the wires, offset them along the length as shown.
Strip the ends of the two white wires, and twist together.
Then, wrap tape over the braided wire splice making sure to also cover the transition from cable to separate wires. The white wire just passes through this bundle.
- "Sorry, no photo of the tape wrapping step."
Fold the white wire splice down flat on top of the other. Wrap one last piece of tape around it to insulate.
Move the knot as close as possible to the splices. Gently slide the strain relief up against the knot. You may find the knot fits partly into the strain relief. Insert the splices carefully into the small space available within the adaptor block.
Reassemble, Close the Case, and Test.
Reassemble the two halves of the case around the adaptor block, tucking in all the wires, and sloting the strain relief back in its groves.
Seal the two halves just with tape for the moment - test your repair before securing it any more than that.
Test.
- "I used big plastic cable ties to hold it together."
"...just use black electrical tape for a few weeks to confirm the repair holds."
"yes that is a spare 2400 screw cover "dot" on my case - where else would you keep it!"
Congratulations!
- "I used big plastic cable ties to hold it together."
- Sealing the Case More
Permanently
The final job, a luxury possibly, is to completely reseal the case.
- "I've used PVC/ABS purple primer and ABS plastic cement
and it worked very well. It's the type you would use when
putting together your lawn sprinkler system. Just mask off
the outside of the case, prime, and apply cement. Use a
couple of spring clips until the cement sets up. Since the
ABS cement is black it blends nicely with the plastic case.
In fact, you can't even tell it's been taken apart if you're
careful in doing a neat job. All these materials are
available at your local Home Depot(local building supply
store for those of you not in the US/rpm)."
(We are looking for a nice closing shot for this 'Sealing the Case" segment if anyone has a photo)
- "I've used PVC/ABS purple primer and ABS plastic cement
and it worked very well. It's the type you would use when
putting together your lawn sprinkler system. Just mask off
the outside of the case, prime, and apply cement. Use a
couple of spring clips until the cement sets up. Since the
ABS cement is black it blends nicely with the plastic case.
In fact, you can't even tell it's been taken apart if you're
careful in doing a neat job. All these materials are
available at your local Home Depot(local building supply
store for those of you not in the US/rpm)."
Additional Suggestions / Further Improvements :
Cable Reinforcement: Several suggestions came in regarding preventing future problems by reinforcing the cable where it meets the strain relief and spreading the stresses over a greater part of the cable...
" I have used both volcanic tape (which when strained and warped molds to the surface), or shrink-wrap (thin rubber tubing which shrinks when heated). The tape is good but expensive. Shrink-wrap is cheaper (but needs to be slid onto the cable before you push it back through the strain relief).""Keep in mind that although adding reinforcement spreads the load over an increase amount of the cable, if too stiff this can lead to problems when packing the power supply into bags etc."
Cable Replacement: There is always the possibility of completely replacing the cable...
"As a DJ, the abuse I gave my headphones (Sennheiser HD414) was pretty harsh, and it wasn't long before I had to replace the cables. They were thin, coaxial copper wire cables, only slightly smaller than the 2400's power supply cable. After two replacements, I was getting a little tired of the repetition! Sennheiser came out with STEEL cables. About the same size, but noticeably stiffer, they lasted several years."
Hope all this helps some other 2400 owners out there.