Apple IIe Power Supply popped and now dead

Those X2 caps (commonly referred to as "RIFA caps" because RIFA was the brand normally used in Astec and Dynacomp powersupplies used by Apple) blow frequently.  Unfortunately when they do they often pop the fuse and/or other components.  I'd start by replacing all of those large caps like that one and the fust if necessary.  If that doesn't do it then you'll need to start troubleshooting from there.

And yes, you can easily remove those and purchase replacements.  I bought some through Aliexpress, but places like Mouser, Digikey, JDR, etc, should also have them.

The chirping and flashing power light is generally the sign of a short circuit. The power supply is essentially starting up/shutting down/starting up/shutting down...

Something must have shorted when the X2 cap died. You will need to troubleshoot the board by hand using a multimeter (in continuity mode) looking for a short circuit and replace any bad components. If you are not into electronic repairs, you may need to inlist the help of someone with experience in this area.

Make sure you remove all cards from the expansion slots when testing to confirm whether it is the motherboard or an expansion card that has the short circuit. If after removing all expansion cards you are still getting the chirping, you know for sure that something on the motherboard has shorted. If after removing all expansion cards the problem goes away, try reinserting the cards one at a time until the chirping returns and you will have identified the offending card which will need repair.

The foul smelling brown goo is what is released from the X2 capacitors when they explode. You are lucky as I have had these X2 capacitors blow twice (in separate //e's) and in both cases they sprayed that brown foul smelling goo throughout the PSU case which required significant cleaning to try and get rid of the odour. The first time it happened the smoke could be smelt in my house for days! :-)

Cheers,

Mike

Yes the components in the middle "coated in caramel" should look like that.

I would probably not arbitrarily replace other caps unless they show signs of leakage, swelling or they show a dead short when you meter them.

You should be able to find a schematic for your motherboard here:

https://mirrors.apple2.org.za/ftp.apple.asimov.net/documentation/hardware/schematics/

In particular the files - apple_iie_euro_schematic.pdf or apple_iie_ntsc_schematic.pdf  (depending on which region your //e was designed for).

First Off: If you have access to another PSU, try using that with your motherboard to determine if it is the original PSU or motherboard that has the fault.

As for troubleshooting, I would:

1. Test the PSU with a load whilst it is not connected to your motherboard. Does it still make the chirping sound? If so, the short is almost certainly in the PSU itself.
2. If not, make sure that you have removed all expansion cards, and reconnect the PSU. Does it still act like it is shorted? If yes, then the short is probably on the motherboard. If not, then the short is in one of the expansion cards. Install them one at a time until the short comes back - then you will know which card is bad.
3. Depending upon where the short is (PSU, motherboard, or expansion card), I would start by looking for a burnt out resistor or capacitor that has failed CLOSED to ground - i.e. the resistor shows no resistance (continuity testing a resistor with no resistance will produce a beep); likewise for a capacitor. Use this method to find any suspicious component(s) and replace it/them.

Testing components in-circuit can be problematic, but generally you should not have resistors or capacitors that are CLOSED or have essentially no resistance between the two terminals. With capacitors, you can expect to get a short beep while the capacitor charges up, but it should not beep continuously.

It's difficult to be more specific due the fact that the short could be in any number of places.

There are far more qualified electronics people out there than me that might provide more in-depth troubleshooting advice. But that might be enough to get you started.

Hopefully you will be lucky and can identify where the short is. If not, you may need to seek further assistance from someone more qualified than me.

Let us know how you get on, and good luck!

Cheers,

Mike

I've repaired hundreds of these things over the years and the only time you will see a dead short is on the mains side of the supply, either the bridge rectifier or the switching transformer.

Your  supply is chirping so neither the bridge or switching transformer is faulty.Chirping occurs when excess current draw is detected on the  +5v output.  It does that by tripping an SCR when +12v get too high. When the SCR trips it stops power to the feedback circuit and stops the oscillations that drive the switching transistor.

Deteriorating capacitors that will look fine to a multimeter is the most common cause due to internal current leakage.  It could be a failed zener in the SCR trigger circuit but that is unlikely. It could also be a short on the motherboard.   Try it with nothing plugged into the output, if it chirps with no load then the supply has issues. The 2e supplies should not need a load if they are functioning within spec.

If it chirps with no load then my advice is to recap the supply  if some caps are leaking then the others are probably failing too or wont be long before they start to fail.It's a 2e power supply they have a high capacitor failure rate,  when I refurbish machines the older 2+ power supplies often dont need a recap but the 2e supplies almost always show signs of leaking capacitors.

So it sounds like you have a short somewhere on the motherboard. Most likely it is one of the chips so you will have to start removing them until the short goes away. If you remove all of the chips and the short persists, then you either have a bad passive (e.g. capacitor) or a trace short (less likely since the board was working).

If you have a good ohmmeter, you can also try tracking down the short trace by trace. Start at the power plug (which should show less than 10 ohms) and then follow the traces toward the area where the resistance drops even more.

Easy fix, it will be one of the axial tantalum capacitors near the power connector next to slot 1.

Check them with a multimeter, one of them will be short circuit.

When you use a multimeter on a capacitor you should see the resistance start low and increase in value over a few seconds as it charges.

What you are looking for is one that doesnt behave that way.

But since you most likely have a short already, you will need to disconnect one lead of the capacitor to test that way to make sure you are not reading the short from somewhere else.

Since you are reading a short across C15, I'd start there. Lift one lead and check directly across the cap. If it still shows a short, then you've  found your problem. Otherwise keep checking the trace where you removed the lead and start removing chips.

This is with your multimeter set to the lowest resistance range (R X 1). Don't use the continuity mode.

Don't replace anything until you find out what is bad. Again, I'd start with C15. In fact, after disconnecting one lead you could try powering up the computer. If that was the bad cap, it should at least turn on. If not, check the other black caps near the power connector. The mustard colored ones are not likely to be the issue.

Once you find the bad cap(s), remove them and take them to your shop. They will be able to give you replacements. Make sure you put the replacements in correctly with the + side aligned to the marking on the motherboard.

Good work! It looks like you found the cause of your short. You can try re-connecting C15 but I suspect that both of these caps will need to be replaced. After that, you still may have other parts that were damaged when the supply blew. 

I don't believe your current issue is due to the caps being removed. They are just filter caps that smooth out the power supply are surely are needed to keep the computer running reliably under various loads. But I would still expect the computer to run without them. Nevertheless, after you replace them if this issue persists you will have to do some fairly detailed troubleshooting. An oscilloscope will definitely be of help here.

Lots of troubleshooting info online. Here's a good place to start (courtesy of fellow fritter SpeedyG):

http://www.appleii-box.de/H198HomeRepairGuide.htm

Maybe this will help:

https://www.classic-computers.org.nz/blog/2011-05-04-apple-iie-adventures3.htm

Your problem is probably not specific to the PAL version, so try any repair suggestions relevant to all Apple IIe's.

robbo007 wrote:

I've just replaced the 4 capacitors mentioned above on the motherboard. After running the built in self test with Control+closedd apple+Reset I get a Kernel OK after. Looks like the board is backonline. Just need to finish the power supply. 

Hello! found your post and it looks like i have the same issue!, also from an exploding filter cap in my psu! so very similar, could you please tell me the specs of the caps (c9 to c17)  you brought ? thank you!

I bought Nichicon "PW" series. Failing that, Panasonic "FR" series. Same capacitance, same or higher voltage. Be aware they will be MUCH smaller than the original (40 years of innovation!)

tony359 wrote:

I bought Nichicon "PW" series. Failing that, Panasonic "FR" series. Same capacitance, same or higher voltage. Be aware they will be MUCH smaller than the original (40 years of innovation!)

Does the PW or FR series comes in axial form factor? or it does not matter?

I could not find Axial capacitors - if you bend the legs and put a little isolator, it'll look good.  (You could run the legs above the caps if that helps). Does the main PSU have axial caps? I can't remember. 

IMG_08552.jpeg

tony359 wrote:

Does the main PSU have axial caps? I can't remember. 

Thanks for the tip! will def try if i dont find axial. Not really sure if psu have axial, the caps im referring to are the ones up the power intake in the motherboard (c9, c12, c15, c,17)

Personally I would prioritise a good quality capacitor (low ESR, long life, high temp) over an average quality axial. The PW series of Nichicon is designed for Switching Mode Power Supplies, so on the motherboard I would personally select the FR series.

That said, my //e motherboard does not have any electrolytic at all! But I may have seen pics of later models which do.

Another tip: if you have plenty of space, you can just keep the capacitor standing up and just stretch its legs! The ones in the picture are from the Disk ][ and I had to use that trick as the metal cover ends up being very close to the logic board.

tony359 wrote:

That said, my //e motherboard does not have any electrolytic at all! But I may have seen pics of later models which do.

They are —from what i learned— tantalium axial caps, hard to find here in mexico, mouser is charging me 44 usd for 5 caps+shipping to mx :/

I'll try to find same specs but different form factor, and make use of those tips. thanks!!

I'm not sure you need to replace tantalium caps. Yes, they can fail but I am not sure I would do that. Electrolytic caps are more subject to fail and I feel it's wise to replace 40 years old ones. But tantalium... If you really want to replace them you should be able to replace them with plastic ones and definitely not electrolytics - but I will leave others to answer this.