Macintosh SE powered off unexpectedly, strong electrical smell

Hey y’all,

after finally being able to use my Macintosh SE (it had been sitting unused for weeks due to a faulty floppy drive while I was waiting for replacement parts from overseas), I ran into an issue today that I wanted to document and ask about.

Earlier today my BlueSCSI arrived, and before switching over to it I wanted to create an archive of the internal hard drive, as it contains some software I’d like to preserve. Disk Copy gave me a bit of trouble, so this involved some trial and error, and the SE ended up running continuously for roughly two hours.

I then briefly left the room to say good night to my cat and when I came back a few minutes later, the Macintosh was completely powered off. The entire room smelled very strongly of burnt electronics.

I immediately went to the outlet and cut the power. I did not attempt to turn the machine back on but it is possible it still had power for at least 8 minutes.

After a few minutes to calm down, I opened the SE for a visual inspection only (no touching of course). I couldn’t see anything obviously damaged or burnt. My assumption is that the RIFA capacitor in the power supply failed. I didn’t personally see any smoke, but the SE sits directly next to a wide open window, so any smoke could easily have went outside before I returned. Even so, the smell remained very strong for at least 50 minutes afterward (counting).

I’m not planning to apply power again until the PSU has been serviced. While I do have a fair amount of experience repairing vintage Apple hardware, I’m honestly very uncomfortable working around high voltage components, especially in CRT era machines. I did a Floppy repair on it a few days ago but this was my pain tolerance.

So my two questions are:
1. How safe is it to service or recap a power supply in an 80s Macintosh like the SE?
2. Does this failure pattern sound consistent with a RIFA capacitor, or are there other common PSU faults that could produce a similar smell and sudden shutdown?

I know RIFA failures are notorious for producing a lot of smoke and an extremely persistent smell. I didn’t witness smoke directly, but the odor is by far the strongest I’ve ever experienced from electronics, even though it didn’t smell "fishy" as often described, just strongly of burnt electronics.

Thanks a lot!
 
There are no failure-prone RIFA safety caps in the SE power supply or on its analog board. You were having some display issues before this happened, right? I suspect the flyback transformer is what failed.

The SE and SE/30 power supplies are compatible, but you may need an analog board repair, not a power supply.

Also, you can use the initiator mode on BlueSCSI to copy the contents of the hard drive to an image on an SD card without another computer involved, as long as you have a way to power the hard drive.
 
There are no failure-prone RIFA safety caps in the SE power supply or on its analog board. You were having some display issues before this happened, right? I suspect the flyback transformer is what failed.

The SE and SE/30 power supplies are compatible, but you may need an analog board repair, not a power supply.

Also, you can use the initiator mode on BlueSCSI to copy the contents of the hard drive to an image on an SD card without another computer involved, as long as you have a way to power the hard drive.
Thank you for your response!

That does make the situation a bit more concerning, since a RIFA would obviously be a much easier fix than a flyback transformer.

That said, I didn’t notice any display related issues prior to this happening. The only thing I observed was a slight tilt of the CRT (the left side appearing a bit lower than the right), but it was very minor and I heard that many old CRTs have them. I never experienced any flickering, strange noises, arcing, or other obvious symptoms that would point to a flyback failure.

If the SE and SE/30 power supplies are indeed compatible, I’m still hoping the issue is PSU related, but the flyback definetly makes sense, especially since it only smells like burned electronics and not fishy.

Unfortunately, I have the DB25 variant of the BlueSCSI, so I can’t connect it directly to the internal hard drive to use initiator mode in this case.

At this point, I think the safest next step for me will be to bring the SE to an old radio/TV repair shop and have them take a look. especially since a potential flyback issue is now on the table.

Thanks again!
 
Maybe you can troubleshoot the issue, have you voltages at the molex side ?
Thanks for the suggestion!
I haven’t taken any voltage measurements yet. Given the sudden shutdown and the strong burnt electronics smell, i decided not to power the machine on again until it’s been properly inspected. I’m not very comfortable doing live measurements in a CRT system (honestly, even with it powered off 😅), so I’m planning to have the PSU and analog board checked by a professional first (if I can find one).
 
One additional detail I just remembered: when I returned to the room, the SE was completely silent and had no fan noise at all. Normally it’s quite audible. That makes me think the PSU shut down entirely rather than a flyback issue.
 
what does electricity smell like
By „electricity“ I meant the typical burnt electronics smell. I can’t say for certain whether it was ozone, but I don’t think so, especially since the fan was completely off when I returned. It smelled more like overheated components or burned insulation. The odor was very strong and lingered in the room for quite a while after the shutdown. It didn’t smell fishy or ammonia like, as failed capacitors are often described.
 
Back
Top