Repairing laptop computer power supplies

[Mr. K]

Our school has a number of power supplies for laptop computers that are out of service because the DC output wire has frayed or broken at the end of the strain relief at the power pack. Electrically, they're still good. The power packs are sealed plastic units (perhaps 4" x 2" x 1 1/2") with a visible seam around the "equator" where the two halves of the case were originally assembled. It appears to be a lap joint which has been glued together. I believe that if I could open them up and then satisfactorily reclose them, cord repairs would be pretty simple. Since these units cost nearly $100 each to replace, I have incentive! <p>I've considered using something like a Dremel or a jewler's saw to cut the case at the original assembly seam, but this would obviously destroy the overlap of the two case halves. I'm not sure how to reassemble the unit in a manner that will stand up to the abuse high school kids routinely dish out. Does anyone have any experience or suggestions? <p>TIA!

[Dave Dixon]

Mr. K,
I would suggest buying new, cheap enclosures. Something like this...
Enclosure here
Only costs around $4.00 or so, and has screws for easy access the next time the wires break.
Hope this helps,
Dave

[jollyrgr]

Radio Shack sells cases like those pictured at Newark and are usually local.<p>As far as how the case is sealed, I believe they are ultrasonically welded. But a Dremel will solve that problem. I can also suggest another solution to the case problem. You can get heat shrink tubing and place it around the case once repairs are made. You don't have to cover the entire power supply, just the ends. I have seen heat shrink tubing up to two inches in diameter. In case you are not familiar with the stuff heat shrink tubing is plastic similar to that of a drinking straw. You slip it over wires (normally) and heat it with a heat gun. (I've also used a hair dryer successfully.) When heated it shrinks around the wire or, in this case, power supply case.<p>As always there is duct tape.

[jwax]

Ideally, you cut out the area of the case that you need to, to get access to the leads, do your repair to the wires, and add a strain relief. Many types of strain reliefs are available.
Then, a 2-component epoxy is poured in to seal the strain relief to the housing.
John

[Will]

Mr K,
If I am reading you correctly, a principal requirement is to have the outside dimmension remain exactly as before so that the whole will fit back into the lap top ? - This is what I have done before and it worked for me !
Cut the assembdly open carefully as you proposed - Might a hacksaw and hacksaw blade make a neater, narower cut than a Dremel ? Then when you re-assemble it just put spots of two component adhesive (Perhaps even super glue ?) at various points on the joint and around the whole and it will work OK. If it seems necessary in order to keep the glue off the internal components then, after or during assembly, place small pieces of paper, cardboard, thin plastic ? inside the case and co-incident with the points you choose to place the glue at. Even stick this pieces to one side of the case before you assemble ? Hope this helps

[Chris Smith]

I cut them open with either a hot exacto knife, hack saw or a jewelers saw and glue them back together with a either PVC glue ABS glue or epoxy. To strengthen the missing over lap, place ½ inch wide strips of PVC or ABS plastic cut from another box,.... inside of one half of the case prior to re-assembly, whole or just two small strips per side and one for the top and bottom like pegs, and glue it there to replace the over lap. <p>Clean the two halves up before fitting them Back together, and when you apply the primer and lots of glue, you can re-shape and smooth the rough edges out quite easily when the glue melts the joint. Let it sit for 24 hours, if its ABS. That or replace the case?

[Mr. K]

Thanks for the suggestions.<p>This link goes to a site that has units which appear physically similar to mine: http://www.toshibaacadapter.com. Choose a unit, select "More Details", then enlarge the picture to see the assembly more clearly. There is a detachable 6 foot line cord which supplies the unit and a permanently attached 6 foot DC output cord which goes to the laptop. New cases mean that I'd have to create a rectangular hole to support the recessed AC input plug.<p>Duct tape or heat shrink would work fine for me, but wouldn't stand a chance against our "creative" high school kids. <p>Still lookin'......<p>[ September 03, 2004: Message edited by: Mr. K ]<p>[ September 03, 2004: Message edited by: Mr. K ]</p>