Apple IIe Power Supply popped and now dead

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Apple IIe Power Supply popped and now dead

Hi all,

My Apple IIe power supply just popped and died. I've opened it up and I see what looks like a capacitor or something which is labled: "0,1uF@X" has a buldge in it. There is also this dried carmel coated stuff on some of the other componets what that? 

 

Can this component be purcahsed and removeded and resoldered? I cant see anything else dmaangd.

 

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Those X2 caps (commonly

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.

 

 

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ok thanks. I've got a local

ok thanks. I've got a local electronics shop what should I ask for? 

 

Also the mainboard that was connected to this power supply when it blu now does not boot up. The "POWER ON" led flashes and when tested with a working powersupply the power supply makes a soft cherping sound and only flashers the POWER ON LED. I've visual inspected the mainboard and can't see anything burnt out. Where should I start?

 

BTW: here is a photo of the power supply. The big thing in the middle that looks like it coated in caremel is that blowen? Or did it have some protective layer? it looks different to the blown "capacitor carmel" as its not sprayed on the mainboard its only on the actual component. And also the component to its left.

 

 

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Time to Troubleshoot

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

 

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Yes the components in the

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

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Thanks for the reply. I'll

Thanks for the reply. I'll have to get myself a multimeter and read up on the testing process. Should I change any other capacitors while I have it open? 

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I would probably not

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.

 

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Hi Mike,

Hi Mike,

I've got out my multimeter and been trying continous mode but dont have a massive electronic background. I've dabbled with cap replacements etc but not trying to find a probelm like this. From the naked eye the board looks and smells normal. Nothing seems blown.  Which are should I start in and could you explain a little more in detail how and what to look for with countinous mode? 

 

Do any electronic shematics exist for the mainboards?

 

cheers,

 

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You should be able to find a

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

 

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I've repaired hunfreds of

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.

 

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Thanks for the replies. The

Thanks for the replies. The chirping occures when I connect a second working PSU from my other Apple IIe. I have nothing else connected to the mainboard  apart from the second PSU, nothing in the slots. The second PSU works fine on my other Apple IIe with no probems. So it looks like the problem is with the motherboard.

 

The original PSU from this APPLE II blew its cap as you can see above in the photos. But all testing on the motherboard is done on a second working PSU from my other Apple II. I'll get around to replaceing the blown caps on the other psu after I get this working.  This motherboard problem started right after the PSU blew its CAP. 

 

Here's my motherboard, if you could help with the area that you were refering too so I can further investigate it that would be cool. 

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So it sounds like you have a

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.

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Easy fix, it will be one of

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.

 

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David_M wrote:Easy fix, it

David_M wrote:

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.

 

 

Thanks guys, Do you mean the black ones, C9, C12,C17,C15 ? or the mustard colour ones. C10, C13, C18, C16, C92, C93, C91 ?

 

Here are the results from my multi meter:

In continuous mode I get a beep only on two. C12 reading 18.46 and C13 reading of 18.35. The rest read 0 and don't beep.

In normal mode they read:

C9: 875.9

C12: 18,14

C17:6.47

C15:0

C10: 876.0

C13:18.72

C18:4.4

C16:4.2

 

So. Could you explain whats going on here :) thanks. 

 

 

 

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When you use a multimeter on

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.

 

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But since you most likely

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.

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Could you tell me what caps I

Could you tell me what caps I need to buy? The black ones and the mustard ones? I'm going to replace all of them I think. Well the ones near the power connector..

 

Thanks,

Rob

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The reference number or type.

The reference number or type. 

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Since you are reading a short

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.

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