Is it necessary to recap the PSU (Sony)?

[colopick]

I’m currently wondering whether a recap of the PSU in my Macintosh SE/30 is actually needed.
I measured 4.97 V at the floppy connector and 5.19 V at the Molex. On the 12 V rail, I measured 12.8 V at the Molex.
These values seem fine to me, even for running an additional graphics card.

Are there any other reasons to do a recap?
Should I place more weight on the age-related degradation of the components in my consideration?

Thanks in advance for your feedback!

 

[aladds]

The reason to recap is essentially physical degradation of the capacitors. To really know how bad that is you need to take them out and inspect them for bulging, leaking. At that point if they don't have issues you can likely put them back, or maybe reform and then put them back...but at the point you've taken them out, it's usually easiest to just replace them with known good new ones.

I've worked on a number of SE/30 power supplies and the vast majority had at least 50% of the smaller capacitors in a state where they should be replaced, with the remaining 50% not having any physical issues but being at least somewhat out of their rated tolerance.

 

[colopick]

Thanks for the quick feedback!

Caps are already on order — guess I’ll just go ahead and give the PSU a proper recap then. Better safe than sorry

 

[obsolete]

I fell into the "you must recap everything" mentality and did two of these Sony power supplies a couple years ago. What I found was that all of the caps I removed measured good, and none were leaking, so I no longer mess with them. The Sony supplies are high quality. If the voltages are good, I leave them alone.

That said, since you already ordered the parts, might as well go for it. It's not a difficult job, and satisfying to get done, so enjoy

 

[Chuckdubuque]

FWIW I opened a Sony PSU two months ago and it was positively oily with cap goo with puffy caps. At minimum, inspection should always be done before plugging one in that is new-to-you or has been sitting idle for a while. And make sure you know what leakage looks like. This forum is full of pictures from newbies who say "looks pretty clean to me" when it has telltale signs of leakage and corrosion. At this point, I replace all the caps and on really bad ones (like that oily PSU), I look at modern replacement PSUs.

 

[colopick]

Thanks!
I think I’ll just open it up and take a look first, then decide from there.

It’s my first Mac PSU, but after doing a bunch of Game Boy DMG repairs, it’s about time I finally give the SE/30 some love too

 

[Juror22]

I think I’ll just open it up and take a look first, then decide from there.

Good plan - I have a few SE/30s and out of those, four of them had Sony PSUs. One is still in great shape with good voltages and no issues. Of the others, two had caps that leaked horribly and one seemed fine, but after testing all three had to be recapped, along with washing their boards. None of the traces were damaged by the leaking and it appears that I caught them in time.

 

[Nixontheknight]

always recap power supplies on compacts and LCs

 

[croissantking]

always recap power supplies on compacts and LCs

And IIsi units.

 

[Mk.558]

And IIci/IIcx/Quadra 700s.

Pretty much every single one of these is over 35 years old. Respectably decent capacitors from Japan, uh, were relatively inexpensive and there's just no reasonable excuse not to do it. "But the guide said this is probably always OK" -- replace it. You're already in there and what if it fails 2 months down the road?

The proper way to check capacitors is not with voltages, but with a combination of methods. Assuming a capacitor fully discharged, you can start with an ESR reading. This is done with a ESR meter, like the popular DE-5000 meter. Except that reading has to be compared with the the specification on the datasheet, which is probably not available anymore because of 35+ years, which is checked at a specific frequency setting or settings. Accounting of course for the relatively low tolerance of electrolytics, which can vary +/- 20% and still be in spec. Then you want to also check them under load, which requires AFAIK a special tester or the use of an oscilloscope, a basic circuit and a power supply/possibly a frequency generator.

Or, just skip all that and replace all of them.

 

[Nixontheknight]

And IIci/IIcx/Quadra 700s.

Pretty much every single one of these is over 35 years old. Respectably decent capacitors from Japan, uh, were relatively inexpensive and there's just no reasonable excuse not to do it. "But the guide said this is probably always OK" -- replace it. You're already in there and what if it fails 2 months down the road?

The proper way to check capacitors is not with voltages, but with a combination of methods. Assuming a capacitor fully discharged, you can start with an ESR reading. This is done with a ESR meter, like the popular DE-5000 meter. Except that reading has to be compared with the the specification on the datasheet, which is probably not available anymore because of 35+ years, which is checked at a specific frequency setting or settings. Accounting of course for the relatively low tolerance of electrolytics, which can vary +/- 20% and still be in spec. Then you want to also check them under load, which requires AFAIK a special tester or the use of an oscilloscope, a basic circuit and a power supply/possibly a frequency generator.

Or, just skip all that and replace all of them.

Yes. When I recapped my LC III's logic board, I recapped it with Vishay Sprague capacitors, a really reputable brand, and they're still holding up today

 

[mikes-macs]

This forum is full of pictures from newbies who say "looks pretty clean to me"

The Sony in my IIsi started a fire. I heard a pop and then flames and smoke. No pictures.

 

[croissantking]

And IIci/IIcx/Quadra 700s.

Pretty much every single one of these is over 35 years old. Respectably decent capacitors from Japan, uh, were relatively inexpensive and there's just no reasonable excuse not to do it. "But the guide said this is probably always OK" -- replace it. You're already in there and what if it fails 2 months down the road?

The proper way to check capacitors is not with voltages, but with a combination of methods. Assuming a capacitor fully discharged, you can start with an ESR reading. This is done with a ESR meter, like the popular DE-5000 meter. Except that reading has to be compared with the the specification on the datasheet, which is probably not available anymore because of 35+ years, which is checked at a specific frequency setting or settings. Accounting of course for the relatively low tolerance of electrolytics, which can vary +/- 20% and still be in spec. Then you want to also check them under load, which requires AFAIK a special tester or the use of an oscilloscope, a basic circuit and a power supply/possibly a frequency generator.

Or, just skip all that and replace all of them.

I still need to recap my IIci PSU. I’ve only changed out the RIFA films caps so far.