Insulation in PSU of Performa 475

[acn128]

Hi!

I tried to replace the PSU from my Performa 475 (TDK brand) with a RPT-60A.
I bought JST-VH connectors and crimped them to the original cables, so no soldering had to be done to the Meanwell PSU.

To mount the Meanwell in the case, I 3D-printed the base by SpocksBeer (Link to post) in PETG and screwed everything together.

But when powering it on on my workbench (without the computer attached), I only heard a loud bang and the fuse blew...
After a while, I looked inside the case, and it seems that a spark between a heatsink (HS1 on the Meanwell documentation PDF) and the metal case ignited.
I have to admint that I forgot to add insulation between the PSU and the upper case, so that might have been the problem...
(Oh, and the PSU seems to be dead now...)

My question here is: Do I have to take anything else into account before burning the next RPT-60A?
I've added a layer of duct tape and electrical tape on the cover.
I also included the connection between the outer case and the two screws M1 and M2 as noted in the documentation.

Do I need to add something else?
I have a new RPT-60A here now, but I don't want to kill another one...

Thank you very much!

Regards,
Anna

 

[dalek]

I personally would be worried that the electrical tape will eventually come unstuck with the heat from the PSU. I think you might have a touching issue at the sides of the heatsink too?

It will "probably" be fine but I'd suggest a proper thermally and electrically resistant product made for the task. e.g. I bought a pack of these https://au.rs-online.com/web/p/plastic-film/7757797 ages ago and it has lasted me forever. You can also scavenge similar material from old/broken PC power supplies etc. Or google thermal electrical insulation and there are a stack of options.

Airflow in there looks like it might be a problem too - maybe add in a small slow fan in the empty space?

Also - I think those meanwells have a fuse buried in there somewhere, though I think it's at the input not at the output where you likely had the short - might be worth digging in to it and see if it's blown and can be replaced.

 

[acn128]

Thank you for your answer!

The heat could be a problem for the electrical tape, yes.
I guess that Kapton tape should also work? I have a roll of it at home...

I will also insulate the sides even more, so that this should not be a problem anymore. I was worried as I saw that some other users did replace the PSU with this Meanwell model, so I thought that it should be a little more straightforward

I've looked for a fuse but did not see one that could be replaced...

So I'll try it with kapton tape and hope for the best.

Thank you!

Regards,
Anna

 

[cheesestraws]

The datasheet does say to be careful never to short the heatsinks together. I put some plastic insulation on top of mine, but arguably I should have put it down the sides as well - and yes, careful with the heat tolerance of adhesives. You don't want it to come off without warning.

Heatsinks in PSUs are relatively often at unexpected voltages, and it's usually best to assume you can't let them too close to other metal parts.

Could have been worse, the case of the PSU could have come live

 

[Bolle]

Could have been worse, the case of the PSU could have come live

I ALWAYS check for that not being the case once everything is assembled when modifying power supplies to go into cases they weren't originally supposed to go in... before plugging it in that is.

 

[cheesestraws]

I ALWAYS check for that not being the case once everything is assembled when modifying power supplies to go into cases they weren't originally supposed to go in... before plugging it in that is.

Yeah, same: check safety earth is in the right places, and that the case isn't live.

 

[acn128]

Hi!
Thank you for the hint. I will insulate the top and the sides.

I also was prepared to check the voltage on the metal case against GND. But at least, the case is also connected to the green/yellow protective earth, so that should prevent that (and even might have been the reason for the fuse to pop).

I'll work on the PSU over the weekend or the next week, I have some other tasks to do before I have time for it again...

Have a nice weekend!

Regards,
Anna

 

[cheesestraws]

But at least, the case is also connected to the green/yellow protective earth, so that should prevent that (and even might have been the reason for the fuse to pop).

Yeah, think so.

Glad you're taking the safety earth seriously. Sorry if I sounded a bit neurotic, but some people don't really take much notice of it and that scares me...

 

[acn128]

Glad you're taking the safety earth seriously. Sorry if I sounded a bit neurotic, but some people don't really take much notice of it and that scares me...

No problem
I also did read the PDF from Meanwell and connected the two screw points together and to the case...

Regards,
Anna