Replacing the Capacitors in an Apple ][e Power Supply Unit.
While, yes, this subject has been raised here previously, I felt it was time for an update (the referenced site below was updated this month). Two days ago the "magic smoke" appeared above the power supply on an Apple ][e. Actually, it was only "semi-magic smoke" as the power supply unit (PSU) kept working. But I know enough to shut off and unplug smoking electronics immediately. Also, research reveals that the failures cascade to a worse condition if you keep using a PSU in this condition (damaging the mother board).
THE BIG STANDARD WARNING:The PSU is not a user serviceable part. Anything you see here is not to encourage you to service it yourself unless you are fully aware of the high voltage capacitance in these circuits that can electrocute you and kill you DEAD!!! DON"T DO IT unless you know what you're doing.
Having said that, I now bow to the combined knowledge here with the following question: If I have thoroughly disconnected the PSU, open mine up, wearing the thick rubber electrically insulated gloves, and discharge each and every capacitor manually, do I have to worry about any other charges? I also know that when the danger of leaked capacitor fluid, which is carcinogenic, needs to be completely cleaned up, etc.
Obviously I want to do a re-capping job on my PSU. I found a good, recently updated site with some good information, including a parts list, (though I note that the filtering capacitors information is not as detailed as Speedy has previously posted here on the AF board).
Apple //e ASTEC AA11042C PSU Circuit Design
I plan to proceed with this if it's economically feasible. I know that ReactiveMicro will do the job for $90 per PSU. Is it worth it? Probably. But how much does it cost to do it myself? Is replacing the caps enough? Are other components robust forever, or are some others about to fail too? Is it better just to get the modern $40 PSU replacements? I'm not a purist, I don't have to keep the original equipment. But if fulfilling the parts list costs around $20, I'd definitely do the re-capping myself. I'm probably going to do about 10 of these PSU's, so a somewhat bulk purchase will save shipping costs.
I'm by no means an expert, but having said that I have serviced numerous Apple II PSU's in the last 14 years.
To make the PSU safe to work on, you need to discharge the large high voltage capacitors in the AC side of the PSU. There are usually one or two large 200+ volt capacitors - these are the ones most likely to do you harm. Most of the other capacitors are fairly low voltage and are not really of too much concern. The "magic smoke" from PSU's usually comes from the rectangular capacitor which is there for line noise suppression (they operate over the incoming mains supply). A PSU will (in most cases) operate fine without these, but it is probably best to replace them (they are readily available). In the cases where I have had the "magic smoke" released, it has also released a foul smelling brown goo throughout the inside of the PSU encosure including sections of the PSU PCB. This stuff is hard to clean up, but worthwhile as it stinks!
If you are comfortable replacing capacitors in the PSU it will save you a lot of money as the cost of all the capacitors combined is probably less than $20. But you need to be comfortable and competent in doing the replacement.
While no component will last forever, it is the electrolytic capacitors that have a tendency to fail the most. Especially when the PSU has not seen service for a long time. The fluid inside the capacitors dries out causing the capacitor to fail. You will occaisionally need to replace other components, but swapping them all out is generally not required or advised. Pretty much use the "if it aint broke don't fix it" rule.
But yes, I agree with your previous comments - don't even attempt to service a PSU if you don't know what you are doing.
Anyway, that's my 2 cents worth.
I recapped my Apple // PSU even before I powered it up when I purchased the system.
The trick is to get the correct capacitors - I mean, any cap would probably work but you may want to use good quality, low ESR, 105 degrees rated ones. I've recently discovered the "PW" series from Nichicon which is designed for switching mode power supplies. Failing that I like the FR series from Panasonic.
The "RIFA" filtering cap must be replaced with a Mains Rated cap - I think they are called X2 rated cap. I replaced it with the same type, other may have other recommendations as the RIFA cap may not be the most reliable one. But I'm sure it'll be fine for many years!
I always replace one cap at the time, double checking capacitance, voltage and polarity every time. Remember modern capacitors are much smaller than the ones you will find in the PSU. If you cannot find the same voltage rating, a higher voltage rating will be ok.
Before you plug the PSU I would run it on its own and check all the voltages. This is helpful so if something goes wrong you do not damage your motherboard.
Remember a PSU has potentially lethal voltages inside so do that at your own risk!! :)
Hi, sounds like the Rifa cap smoked. Have you looked at:
It looks like they sell recap kits for the
Has anyone purchased these? Are they namebrand caps?
I've bought a lot of kits from Console5 over the years, including most recently for my IIgs power supply, main board, and RGB monitor. He only uses 105c Nichicon and Panasonic caps for electrolytic (exception being for kits where he supplies axials like the Disk ][ kits he sells, they are 85c Nichicons). For the Rifa cap, I'm not sure what brand was in my IIgs power supply kit. But I'm sure it was name brand.
In addition to selling the cap kits for older computers and video game consoles, he's put a lot of time into documenting all the different revisions of hardware, the cap lists, and even cap maps of the orientation of the caps on his tech wiki. He's a good guy and highly recommend him and his kits.