Apple II power supply help needed...

I have an Apple II and the power supply went pop as soon as it was plugged into the mains. It hasn't been used for 20 years so it was kind of expected.

Anyway due to the fumes and the smell I assumed it was a cap but upon opening the PSU it appears to be something else.

In this picture they called it a Transient Filter:



From what I can see it appears to have cracked. I'm a little nervous around the unit as I know they can be quite dangerous. Does anyone have any idea what this part is and where I can get one if at all and also does anyone know how I can safely remove the board from it's box without killing myself. I'm ok with electronics but I have been told to be extra careful around these things.

Thanks in advance.

EDIT: It appears to be a paper capacitor.

 

I'd do some research into discharging this thing properly before you do anything with it mate, a blue flash might be the last thing you see if you stick your finger or a screw driver in the wrong place.

Not sure there's an abundance of knowledge here on retro apple PSUs, I'd check in at one of the apple retro forums for that really. :/

At the end of the day the only option may be to replace the PSU completely as I heard many of those components are bespoke to that machine (might be thinking something else here though). But again, I'm certainly no expert...

 

They aren't overly high voltage or anything - not like messing around in a crt.

Also a power supply is a power supply for the most part, being apple 2 specific doesn't overly make much difference - other than the fact someone on that type of forum may have ran into it before.

 

That's why I was being specific, just incase someone here had worked on one before and new straight away what the part was. I feel better now you've said that it's not going to be as dangerous as I first thought. I took a shock from a modern iMac across the heart (both hands) a couple of months ago and that was bad and I survived, guessing this can only do similar, so I guess I'll suck it up and get on with it.

On another forum they've told me to buy one of these: http://www.jaycar.co.nz/productResults.asp?MID=1&SSUBID=636&SUBCATID=967&keyform=CAT2#1 so I just need to find out what rating it is and find somewhere in the UK which sells them which probably won't be too difficult.

 

put it this way, I pull out DC psu's all the time. Sometimes left plugged in by mistake and other than a 240v shock (which im used to, once being an apprentice electrician) - its not a huge deal.

Dont get me wrong, dont go ignoring all safety concerns, but its certainly not like working in a CRT - where odds of death can be pretty high.

Anyway, back to the point...

Any pictures of your actual unit, rather than one off the internet?

 

I can't get any decent pictures of mine until I get it out of the case (which I'm going to do tomorrow) I can only see the damaged component at the moment by looking it at a funny angle which my camera won't pick up as it sits under the power cord socket which is currently riveted into the case.

Only thing is, the parts the other forum have suggested don't seem to match the part which has blown on my board. Is it just that the more modernised parts are smaller and look different or have they misinterpreted what I've said. Just to re-interate the part on mine that has gone is the component with all of the numbers across the top on the far left hand side, doesn't seem to match the parts in the link I posted.

 

Yes, capacitors come in different shapes and sizes.

 

That's why engineers often use isolation transformers and variacs on old equipment - to protect yourself.

There's a chance if you replace just the capacitor, it'll happen again. It is set to 240V, right?

Incidentally, there were several versions of the Apple II PSU - 4 or 5 IIRC. If you're using a service manual or discussing with someone, it's worth noting which you have. I'm not sure where my copy is offhand, so I can't advise what the capacitor should be right now. I would suggest checking all the electrolytics and diodes, though. It wouldn't hurt to check the bridge rectifier, too.

 

on mine (apple IIE) same symptom (pffff sound then plastic burn smelt), it was the rectifier bridge capacitor (0.1 µF 400V IIRC), I've replaced by one from an old classic computer PSU.
And works flawlessly since.

 

Yup it's set to 240v, first thing I checked. As far as I know with the IIe only two PSU were used an Antec branded one and an unbranded model. The Antec one is apparently the "safer" of the two to repair which is the one I have.

That sounds about right. Anyway tomorrow I have some time off so I'm going to desolder the part so I can get a closer look and identify it properly before seeking out a replacement.

 

comp.sys.apple2

usenet group, bunch of old Apple II peeps there, active group. They can give you any pointers/tricks for fixing the power supply.

 

Well I finally got the thing apart and it turns out what blew wasn't actually on the power board itself (which is good as it hasn't leaked anything on to it) and was intact directly connected to the female power socket on the casing.

I've taken it off and snapped a few pics. Hopefully someone can help me work out what it is and hopefully help me find a replacement:

 

It's a capacitor - 0.47uF is the value, the "X" is a safety marking (designed for use directly across the line). 250VAC is the rated operating voltage, Fo=1.9MHz is the self-resonant frequency, MP is the material it's constructed from (metallised paper). The "VDE" "S" "N" "D" and "OVE" markings are safety agency approvals. GPC 40/085/56 is an IEC environmental category. Rifa is the manufacturer (now taken over by Kemet) PME271 is the series and the "M" indicates +/- 20% tolerance.

That part appears to have been discontinued - I would recommend replacing it with one of these:

http://www.digikey.com/product-sear...keywords=PME271M647KR30&x=0&y=0&formaction=on

It's the same basic series, but with an X2 safety rating rather than X, a slightly higher maximum operating voltage (275VAC vs 250VAC) and a closer tolerance (+/- 10% rather than +/- 20%) - I.E. all the specs are the same or better.

 

Would this be appropriate?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=221080802820&ssPageName=ADME:L:OC:GB:3160

 

It looks fine, although it has a much higher voltage rating than needed. Thats not really a problem except usually higher voltage rating caps are bigger. As long as the lead spacing is the same and it will actually fit on the board then i don't see much wrong with it.

EDIT: Nevermind, it specifies 275VAC at the bottom. Looks almost identical to what was posted earlier on digikey.

 

Good stuff, ordered one. I read on another forum that the 275VAC shouldn't matter. Do these things have polarity? I can sort of match it up to the existing one but I can't rely on them being manufactured the same way around.

 

No, those sort of film caps are non-polarized. Since it's an "X" cap, it's presumably just wired directly across the AC line anyway.

 

IT LIVES!!!

 

Good to see the Apple II returning from the grave!

Let's celebrate!

 

Nice!
I regret that I threw away my broken Apple II several years ago