• Please review our updated Terms and Rules here

Q: Recapping an Apple II Plus Power Supply

oldpcguy

Experienced Member
Joined
Sep 23, 2021
Messages
366
I need to recap my Apple II Plus power supply, model number 605-5703 / ASTEC # AA11040/B. I purchased the appropriate recapping kit from:


When I began the process of recapping the power supply the first thing I did was to take pictures for orientation (to note the positive and negative leads along with notating whether the marking on the capacitor was for the positive or negative lead) and the corresponding capacitance and voltage values. I then compared this list with the parts from the kit and noted the following two discrepancies:
  1. Two of the 1000uf capacitors, C13 and C14, are 12 volts instead of 10 volts (the kit contains four 1000uf, 10-volt capacitors).
  2. One capacitor, C12, is 680uf / 16 volts whereas the kit specifies C12 should be 1000uf, 10 volts.
I've double check the kit parts against the following wiki list:


and they match. I also doublechecked the power supply part numbers (both Apples 605-5703 part number along with the ASTEC #AA11040/B) to ensure I purchased the correct kit for this model power supply. All looks to be in order and matching except for the three capacitors installed in the power supply. I don't believe anyone has recapped the power supply before as I had to drill out the two rivets on the side and the PCB doesn't show signs of any hand soldering.

Does anyone have any familiarity with different model ASTEC power supplies which might explain this? What issues might arise if I were to just use the kit capacitors instead of the values of the installed capacitors? My primary concern would be C12 which varies not only in power rating (10 versus 16 volts) but also capacitance value (1000uf versus 680uf). I should note that I've used this exact kit to recap other 605-5703 power supplies and the parts matched exactly, this is the only one I've seen which varies.

Thoughts?
 
Dont see replacement RIFA capacitors in that kit ?

Of all the capacitors in a vintage PSU, its the RIFA's that explode and the ones I would replace.
 
Dont see replacement RIFA capacitors in that kit ?

Of all the capacitors in a vintage PSU, its the RIFA's that explode and the ones I would replace.
There's a RIFA capacitor included. This is a nice little kit for rebuilding these power supplies. I highly recommend. I've used them to rebuild a few other power supplies and everything needed is included. Which is why I was surprised to find what's actually in the power supply doesn't match the kit, or the parts listing provided by rittwage, or any other Apple II power supply I've recapped. The only thing I can think of is this one is some slight variation but I think I'll go forward with what's in the kit.
 
Ah, didn't see them. For the price it looks fine and a reasonable safety net rather than hunting for each component yourself if you've not got a high turnover of parts :)
 
Ah, didn't see them. For the price it looks fine and a reasonable safety net rather than hunting for each component yourself if you've not got a high turnover of parts :)
Agreed. Buying capacitors piecemeal can be expensive. I found an Ebay seller who sells Nichicon caps and he has been very helpful in putting together "kits" for me and selling the parts for a lot less than if I were buying them individually.
 
Last night I recapped the power supply and it passed the smoke test. Definitely a problem with the RIFA and one of the 47uf capacitors (C5). The RIFA hadn't blown out but it looks as if it may have leaked. The same with C5. Except for the RIFA capacitor I checked them all with my ESR meter and none of them came up obviously bad. But several were, IMO, further out of specification for my preference (of course I didn't perform the math to see if they fell within the tolerance limits). There was goop that needed cleaned up around the 47uf capacitors and associated parts along with the top cover of the power supply. Cleaned everything up with isopropyl alcohol and it's ready to close up and install.


Power Supply Circuit Board - Small.jpg
 
UPDATE: Reassembled the power supply and attempted to power up my system and still no signs of life. Apparently that wasn't capacitor goop (reinforces the ESR meter readings I measured) so something else is wrong. Will be setting this aside for the time being.
 
I’ve recapped a dozen of these PSUs. I use 35v on the 1000uf caps always. I used 10v once like the originals and I had problems. In fact I replace everything with a slightly higher voltage than face value. Just a suggestion. The safety cap (RIFA) should be replaced as they’re known to blow if it’s not blown already. Keep in mind, That safety cap has zero bearing on the function-ability of the PSU. I had one blown apart for months and I never even knew it was blown. But my personal experience is go a little higher on the voltage with the caps.
 
I’ve recapped a dozen of these PSUs. I use 35v on the 1000uf caps always. I used 10v once like the originals and I had problems. In fact I replace everything with a slightly higher voltage than face value. Just a suggestion. The safety cap (RIFA) should be replaced as they’re known to blow if it’s not blown already. Keep in mind, That safety cap has zero bearing on the function-ability of the PSU. I had one blown apart for months and I never even knew it was blown. But my personal experience is go a little higher on the voltage with the caps.
I've already completed the recapping and it didn't solve the problem. I am not surprised as there was a faint smell of something having burnt and failing caps don't result in a burnt smell. But in the majority of cases the problem ends up being bad caps so I was thinking that'd be the problem. Now I have to decide if I want to troubleshoot this power supply or replace it and recap the replacement (I guess I could pull these caps off and use them in the replacement power supply).
 
What is all that burn residue in the pic you posted? I know it can be frustrating. I had a Dynacomp show great readings and after 20 minutes of being on, the +5 volt rail would start slowly dropping (got all the way down to 3.5) and the -5 was doing the same. I fully recapped the unit and it still did the same thing after 20 minutes. My opinion is if the board requires more than a good recap and no broken traces shown, maybe it’s time to retire it. I put that board on the shelf, maybe it will be good for a trade one day.
 
What is all that burn residue in the pic you posted? I know it can be frustrating. I had a Dynacomp show great readings and after 20 minutes of being on, the +5 volt rail would start slowly dropping (got all the way down to 3.5) and the -5 was doing the same. I fully recapped the unit and it still did the same thing after 20 minutes. My opinion is if the board requires more than a good recap and no broken traces shown, maybe it’s time to retire it. I put that board on the shelf, maybe it will be good for a trade one day.
I'm fairly certain it was RIFA capacitor goop as there is a hole in the side. It's my understanding the RIFA will not cause the power supply to fail so I thought that one or more of the other capacitors would be the cause. Unfortunately that's not the case. I see a fuse in the schematic and I'll have to check that, maybe the RIFA failure caused the fuse to open.

Power Supply RIFA Capacitor Damage - Small.jpg
 
I have never seen a rifa cap explode anyhing wet.. Most of the time its just brownish paper powder and smoke.. But hey why not. rubbing alcohol and a cotton swab will get that off. Its most likely corrosive in the long run so you will want to be thorough in cleaning that goop off.
 
I pulled the power supply apart, checked the fuse, and observed it was blown. I was happy thinking I just overlooked this when recapping. I installed a new fuse, performed the smoke test, and observed no smoke. Well, that's because it was all contained within the fuse. Yep, it blew again. So something is definitely wrong. Next step is to pull the circuit board out of the chassis and perform a visual inspection to ensure no leads are touching the chassis (doubtful as there's an insulator to protect from just that, at least on the high voltage side). Then I'll check diodes and the transformer (TR1) for shorts.

A little background on this power supply. I purchased an Apple II Plus from Ebay which was advertised as not powering up. When I received it I performed several power on tests over a period of a few days. At no time did it show any signs of life. So I pulled the power supply and drilled out the rivets to check the fuse. All was good. I decided to measure the voltages when plugged into the system so I reassembled it all and flipped the power switch. To my surprise it powered up. I did nothing other than open it and inspect the fuse.

I've heard stories of power supplies, which hadn't been used for a long time, powering up after power had been applied for a little while. Something about the caps getting conditioned. While skeptical this was the case I had no other explanation for it suddenly working and I really didn't care. It was functioning and that was what was important. I then had to troubleshoot some functional issues with the system (which ended up being a bad memory chip). From that point forward I considered the system repaired, used it for a few things, then set it aside to work on other projects. I had considered recapping the supply but decided not to bother with it as it was working fine.

Last week I hooked it all back up and, to my surprise, it didn't power on. Leaving me where I am today. I am not sure why it wasn't working, started to work (with no repairs performed), worked for a few weeks, and then stopped working after it was put up for a few months. I suspect a marginal component is the reason but I can't say with any certainty.

If anyone has any other suggestions please feel free to offer them up.
 
Last edited:
Does anyone know where I can source the fuses? I am unable to locate a 2.75 amp fuse. I can find 2.5 and 3.0 but no 2.75. If I am unable to source the 2.75 has anyone used a 2.5 amp fuse successfully? A 3.0 amp is not that much larger so it may be a substitute. But I'd rather not go larger, even is by .25 amps, if I can avoid it.
 
New question: Do the red and black wires that connect the power connector / switch to the PCB just pull off? I thought I recall seeing a video where the individual just pulled them off. However, when I pull on them they don't budge. I have thought about using something like pliers to give me some additional pull but I don't want to damage them if they're not designed to pull off.
 
Back
Top