How to break ultrasonic welding

[@rt]

Hi Guys,
I have a couple of linear PSUs for retro computing I’d like to replace the smoothing capacitors,
and perhaps even the whole PSU, but preferably save the plastic enclosure.

Is there a common way to open them other than the obvious butter knife?
Cheers, Brek.

[james_s]

I sometimes have luck using a bench vice with a rag to prevent marring the plastic. Squeeze it from opposite corners and some enclosures will crack open along the welds. It's tricky though and some stuff is virtually impossible to get apart without mangling it.

[Towger]

High impact shock.  Aka whack the item along it's seams with the head of a large screwdriver or some such object.

[@rt]

I don’t see it being so easy somehow
http://www.amigahistory.plus.com/commodore/cd32powersupply.jpg

Nothing to loose though I suppose.
I’ve spend enough time & money on the machines, I’ll never be happy with the stock PSU.

[Gyro]

Just double check that it  is ultrasonic welded. Rub over the label on the underside with something hard to look for screw holes. Also look under any rubber feet, another favorite hiding place.

[@rt]

I’ve got one that has been neatly broken, and the PSU replaced,
I just don’t know how they did it.

[mikeselectricstuff]

High impact shock.  Aka whack the item along it's seams with the head of a large screwdriver or some such object.

Mikeselectricstuff showed this technique recently.
https://youtu.be/Iw4wr75YZb4?t=4m8s

They don't usually break that quickly, but I've never had that technique fail, and I've taken a lot of things apart 

[amyk]

High impact shock.  Aka whack the item along it's seams with the head of a large screwdriver or some such object.

Mikeselectricstuff showed this technique recently.
https://youtu.be/Iw4wr75YZb4?t=4m8s

The ultra-sonic screwdriver.

[@rt]

The thing is you’d usually care about the guts,
but here I care about the case, and the guts are secondary... but will try.

[thom]

reviving this old thread to share some info I just stumbled upon. no, this doesn't affec tultrasonic welds, but most of the time these power bricks aren't welded shut, but held together with a solvent.

if oyu don't care about the smell, wick some gasoline into the seam, wait 30 seconds, then wick some more into the seam and wait another minute or two, and it will cleanly pull apart. there are sprays you can buy that do this as well with less smell but they aren't as strong so your mileage may vary.

[richnormand]

I usually use the combo of a vise or a C clamp and listening at the source of the cracking sound.

Then, a 1" wood chisel with a hammer to go around. I find the screwdriver methods leaves to many damaged spots on the enclosure.
Sometime you have to repeat the whole process several times, but it works at the end. Small increments and patience are the key.

Looking for hidden screws and, in a couple of cases, going to a friend to xray the piece! One handy tool is a diamond wire saw to get in the seam and cut there to weaken the corners
while being carefun not to damage the insides. Diamond wire method is much more controllable than using a Dremel.



 

[cantata.tech]

Is there a common way to open them other than the obvious butter knife?

I don't know if this is common, I doubt it, but the obvious tool would be an ultrasonic plastic cutter.

[tunk]

I think I read it on this forum:
Place two 3-4mm drill bits (or similar) on the seams and then put it all in a vice.
This will concentrate the pressure on the seams.

[abdulbadii]

supposing have handy DC motor with its gears to be a grinder, driller, etc, and spudger(s), highly recommended many of it :

get 1 mm (or less) thick grinding disc
just start grinding with it onto part that seems to be the easiest/weakest to open then continued by use of spudger

pry it up mildly strong to judge finding the screwed fastened part
 
if meet a hard/impossible part repeat using grinder just for it, then back use spudger

it'd be most of time, succeed finishing such task

[Swake]

I hope that after 6 years he managed to crack it open 
But thanks for the tips

[WattsThat]

If it has been ultrasonically welded - Place item on a solid surface. Insert a new, heavy duty utility knife blade sharp edge into the seam and smack with a hammer all along the edges. Repeat until it opens. It will. Cleanly. Battery packs are where I learned this. Works for PSU bricks as well.

 It sounds dangerous and probably is if you’re an all thumbs kind of individual. But, it works well with little to no damage of evidence of opening. Re-close with MEK or appropriate solvent cement.

[wraper]

If it has been ultrasonically welded - Place item on a solid surface. Insert a new, heavy duty utility knife blade sharp edge into the seam and smack with a hammer all along the edges. Repeat until it opens. It will. Cleanly. Battery packs are where I learned this. Works for PSU bricks as well.

Only if you are almost blind and don't see a shit. This does not work without significant visual damage. Also it does not work well on stronger welds. Solvent method allows to take power bricks apart with zero damage. You can take it apart, glue it back and there will be no way to find it out by looking on it.

[Original]

Like #15 and also put it in the freezer. The colder it gets the easier it will crack open. If attacked correctly, you will not even need a hammer. Wear gloves watch the sharp edges!

[wraper]

Like #15 and also put it in the freezer. The colder it gets the easier it will crack open. If attacked correctly, you will not even need a hammer. Wear gloves watch the sharp edges!

Freezer helps and I've done it before. But solvent works better and there is no chance enclosure will crack in a wrong place. Also you don't need any blade shit. While cold, put is on some semi-hard surface and smash it with a mallet all around on the seam until it cracks. Blade only does more damage as it's not really pushing pieces apart but only mauling the seam.