Advice Needed Fixing laptop PSU bricks - opening and resealing the cases?

jeallen01

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Afternoon

My biggest impediments to fixing laptop PSU bricks are how to open them without doing too much damage to the cases, and then how to safely reseal the cases after replacing the failed components - so I would be grateful to know the "best" approaches to those 2 issues as I have several failed bricks around and it would be good to be able to fix them safely.

Thanks in advance for any advice.
 

2cvbloke

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My thoughts are that as most OEM power supplies are ultrasonically welded shut, the only way to open them is to use a hot knife tool (basically a lower temperature soldering iron with a flat blade tip), of course this leaves the issue of reassembling the casing in an adequate fashion, such as using glue or solvent welding to re-join the two halves...

I've no experience of cutting open such supplies with the intent of repair, for me it'd be a one-shot deal just to see what went bang before it went in the bin... :)
 

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Like remote controls, drop from about 1.2m onto a hard floor, which will break the seal.

Check there are no screws under rubber feet or filling material first

(There might also be a single screw under a certificate)
 

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I hit around the seam with the rubber covered handle of a large screwdriver.
 

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Have successfully repaired a few (bad capacitors or some soldering\contact gone bad etc)
Tried as best as possible to cut open in a way that made it possible to glue back together without looking too bad, or simply used nylon strips :O)

If repair succeeds but box beyond recognition, maybe put the electronics in a new plastic box ?
 

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A small demidrill tool with a very small circular saw blade (and they make some small ones for that type of tool)has been the best choice for me in doing this type of job.

The bad part is trying to find parts for a switching power supply without a schematic and parts list, electrolytic caps that have blown or a burnt diode are easy fixes, but when it comes to an IC that has charcoaled up it's beyond repair.

As to sealing it back up, if you havent had too much coffee that day and your hands are steady enough, some gel type super glue works wonders, anything that globs out can be sanded away. And I think it even comes in black,
 

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A small demidrill tool with a very small circular saw blade (and they make some small ones for that type of tool)has been the best choice for me in doing this type of job.

The bad part is trying to find parts for a switching power supply without a schematic and parts list, electrolytic caps that have blown or a burnt diode are easy fixes, but when it comes to an IC that has charcoaled up it's beyond repair.

As to sealing it back up, if you havent had too much coffee that day and your hands are steady enough, some gel type super glue works wonders, anything that globs out can be sanded away. And I think it even comes in black,
@Terryl
Many thanks - and I think I was coming to pretty much the same conclusions myself about the tool with which to try to open the cases, and then how to seal them up again although I was thinking more of using a hot-melt glue gun (already having a gun and some black hot-melt glue sticks).

PS: Agree with you about the issues of identifying and replacing failed components - hopefully it'll be the "simple" ones in most cases, due probably to failure of primary rectifiers or secondary rectifiers or regulators. In any case, to try to replace anything more complicated won't be worth the cost.

PPS: already tried to open one of the cases with @PGH's method of belting it with the end of a large screwdriver - but that had no effect and just bounced off! :D
 
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I did, many years ago, and SWMBO chucked a Telecommander in my general direction: Needless to say, she missed by a considerable margin and it hit the floor - It split nicely along the seam without damaging the hidden lugs, so I cleaned up all the key pads and clicked it back together again. Result.
 

2cvbloke

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I was thinking more of using a hot-melt glue gun (already having a gun and some black hot-melt glue sticks).

I'd not recommend hot glue unless it was the higher temperature stuff, the regular hot-snot that we tend to get off the shelf will soften and come apart when the PSU is in use (depending on how much of a load the laptop places on it, mine can get quite hot to the touch), hence the use of other glues, even something like UHU All-purpose glue would work well as that stuff (from experience, both accidental and intentional!) will melt the plastic slightly and create a near weld-like joint as it is solvent-based... :)
 

jeallen01

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@2cvbloke

Good point about the temperatures - hadn't thought about that issue!

Hopefully will get a chance to experiment in a week or so (other things taking precedence ATM)
 

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I crack them with my hands by squeezing all around or put them in a vice with rubber on the vice jaws. I have "Dropped" a few or used a form of impact to open them but I've had inductors break off or smash and the same with small transformers.

With regard to sticking them back together I use Loctite Gel Superglue, the normal runny stuff isn't as good.
 

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Screw and then blows with large screwdriver.
Loctite Gel Superglue, It also works very well contact tail, hold with an elastic rubber a few hours (with better heat), so it opens better next time.:-rofl2
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Tornillo de banco y luego golpes con destornillador grande.
Loctite Gel Superglue, tambien funciona muy bien cola de contacto, sujetar con una goma elastica unas horas (con calor mejor), asi se abre mejor la proxima vez.:-rofl2
 

jeallen01

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Cracked one open yesterday - quite easily, in fact, because the seam along one side had partially opened anyway. Bit of levering with a small screwdriver opened the other side but some slight cracks in the case halves did result. Can't see any obvious signs of burning but need to investigate further (when I have time!).
 

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The most common failure in those things are capacitors. Usually the start-up cap.
 

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The standard fault (if it has an indicator of operation), it flashes.
If consumption is set, the led turns off.
The output capacitors of the switched source are those that suffer, if they do not have coils that stop the peaks of the switching.
With the tester / polymer in vacuum / no load well, with load / consumption, the volts fall.
The "transistor" input and output are cheap.
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El fallo estandar (si tiene led indicador de funcionamiento), este parpadea.
Si se pone consumo, se apaga el led.
Los condensadores de salida de la fuente conmutada son los que sufren, si no tienen bobinas que paren los picos de la conmutacion.
Con el tester/polimetro en vacio/sin carga bien, con carga/consumo, los voltios se caen.
El "transistor" de entrada y el de salida son baratos.
 
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