Recapping the M4896

[croissantking]

Anyone recapped an M4896 power supply, the one that comes with the PowerBook 1400 series? I’d like to do mine. I think in addition to cutting around the seam there is also a Philips screw hidden underneath the label. I’ll document my progress here if no guide already exists.

 

[3lectr1cPPC]

I've opened a 5300 supply, but not that one. Still have to actually recap that supply and get the values - I could definitely use the ones from the 1400 PSU!

 

[croissantking]

I've opened a 5300 supply, but not that one. Still have to actually recap that supply and get the values - I could definitely use the ones from the 1400 PSU!

It's the same, but with a different power connector, right?

Anyway, here's part 1 of disassembly.


First, remove the screw hidden under the label.




Use a sharp knife to cut round the seam. I've done this with my 500 series adapters and it gives a very nice and clean result.


Even after I'd completely cut round the seam, the casing didn't want to open. It seemed stuck together where the screw had been. I levered some more, and it snapped apart. It seems as though the standoff was fused together and visually, looks like I snapped it. But it's fine, since the screw still goes back in and holds it together.


Looks like there's 7 capacitors in total to swap out. I'll list their values and measurements shortly.


The underside of the PCB has an extra layer that will need to be desoldered to get access to the caps.

 

[3lectr1cPPC]

It looks the same from a first glance but I can't be sure as I'm on vacation. I thought it might be different inside since the 5300 supply would be a year older, but seemingly not. Will get the values up on macdat once you have them

 

[croissantking]

I've found some time to progress my work on this PSU, not least because I now have four of them to recap!

Here are all the caps:



And here is a link to a Mouser project that I put together just now.

 

[croissantking]

I whipped up this diagram as a visual aid.

 

[aladds]

Don’t forget the RIFAs or you’ll have a nasty surprise when they inevitably pop

 

[croissantking]

Don’t forget the RIFAs or you’ll have a nasty surprise when they inevitably pop

Are RIFAs really an issue in these? @cheesestraws what do you think?

 

[aladds]

In the photos above I see cracking in C3.

 

[croissantking]

I’ll take measurements and update the diagram later. I’ve never heard of RIFAs popping in anything other than the early compacts, but given that these units are a bugger to open up it’s probably the right thing to do.

I see three RIFAs - a large one at C1 and two smaller ones at C3 and C4.

 

[3lectr1cPPC]

There's a RIFA in the Duo power supply that blows up all the time. I'd replace them.

 

[aladds]

It's my understanding that the reason RIFAs aren't so much an issue in newer devices is because you usually see different brands of Class X/Y safety caps instead of RIFA branded ones, and it's the construction RIFA used which causes the issue, as the resin degrades. You can still get RIFAs made the same way, mind you. No idea if they're any better these days but I'd hope so.

 

[croissantking]

Here's a close up of the RIFAs in my PSU.



I removed them for analysis:



The three other PSUs I'm working on have all Iskra parts instead of RIFA.



The Iskra safety caps are labelled MKP, so they are polypropylene based and safe to leave in.

 

[cheesestraws]

The RIFAs go with age; they may not go yet but in a decade they'll be going in those too. I'd suggest doing it while you have them open. It's only paper safety caps that have the problem.

 

[nathall]

I have a 1400 power supply somewhere that needs repair. Something popped in it a couple years ago and it released the magic smoke. I never opened it but I’m curious to do so now, to see if it was a RIFA.