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Film capacitor Apple II+/e power supply

orlandoave

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There is a .1uF 250V film capacitor that has burnt or blown out in several of my Apple ii computer power supplies.
It is easy to get to in the Astec and the Dyna, except the Dyna has two of them. They are a simple replace.
I am having trouble finding a supplier that has the correct one here in the US.
Any one know of the exact part I am talking about and where to get them?
 

Chuck(G)

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By the sound of it, it's just a line filter cap, which should probably be a safety (X- or Y- rated) capacitor. Polyester or polypropylene versions generally age better and are not expensive, so unless you're picky about "original parts", it should be a simple matter.

Got a photo of an old one?
 

orlandoave

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Thanks Chuck(G) - no sharp photos that you could tell much from. The caps are quite toasty as well.
The information on the cap is as follows:RIFA 40/85/56 fe=4,9 250V 0,1uF@X
Forgive me my component electronics education is way in the past, I can solder and keep these old Apple girls alive though.
I hope this gives you something to go on.
Many thanks!
 

retrogear

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Speak of the devil ... The same thing just happened to me tonight. I was testing a board and after a few minutes heard / smelled it. Shut it off before the program even quit running.
Now the room reeks. I see that cap burned through the side. Guess I'll be ordering that cap too. I see a few others swelled as well.

Larry G
 

Chuck(G)

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David's got the right part, even though the infamous Rifa caps are usually encapsulated in clear or yellow-brownish resin. The important part is the "X2" safety rating.

It happens more frequently than one might think.
 

retrogear

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I've got the caps on order but still question whether the RIFA cap is even necessary. If it's purpose is to keep RFI from travelling back out the AC mains, does it even matter anymore? Who uses analog TV or radio anymore in the home? I'm tempted to just snip it out. I bet it would work just fine. Having an RIFA cap seems like a problem just waiting to happen ...

PS - hmmm, unless it keeps the display from getting squirrelly lines ...

Larry G
 
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retrogear

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Thanks david. I don't like waiting for parts so I might try removing it and see if the family complains about the wifi performance :)

PS - come to think of it, my workbench is not too far away from the wireless router ...
 

hideehoo

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I've been using these Panasonic's to replace Rifa's in most of my old supplies. Bought a couple dozen of various values when they were less than 10 cents a piece at Newark, but looks like only the 0.22uf are the only one's on "sale" currenlty.

http://www.newark.com/webapp/wcs/st...estType=Base&partNumber=58T1725&storeId=10194

http://www.newark.com/webapp/wcs/st...estType=Base&partNumber=49W2075&storeId=10194

http://www.newark.com/webapp/wcs/st...estType=Base&partNumber=58T1731&storeId=10194

The lead spacing on these are narrower than the Rifa's of the same value, but most of the PSU PCB's I've seen/done had over-sized pads with multiple holes drilled so they fit just fine. Last one I had go before a preemptive replacement was a 0.22uf Rifa in an Apple III PSU that made the house smell bad for days.

If you want the exact Rifa 0.1uf replacement (too rich for my blood), here it is

http://www.newark.com/kemet/pme271m610mr30/capacitor-paper-film-0-1uf-275v/dp/11N7706
 

Chuck(G)

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I've got a mixed box of NOS Rifas up to about 2.0 uF, if you're after the real thing, but otherwise, I wouldn't bother with putting the old stuff in gear that's supposed to be used. It's an old design. Modern caps are better. Rifas do seem to have a following in the audiophile community, however.
 
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retrogear

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I unsoldered the rifa and my power supply plus the board I was testing when it smoked work fine. I'm grateful for this thread because when mine went, my first thought was this discussion I had just read the same day and I immediately switched it off. It didn't even blow the fuse !! I will replace the rifa and change some swelled caps, though.

Larry G
 

orlandoave

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I received some new film capacitors from Mouser Electronics to replace the RIFA blown caps in the Apple II p.s.
Mouser part number 539-158X104K. I replaced the blown caps in two power supplies and both now work well.
Thanks to David Schmidt, you were absolutely correct.
 

Malc

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I just left it off, hopefully there won't be any issues.. so far, so good.

Time will tell, After all they were there for a reason, Personally i don't see the point in 'not' replacing them for the little money that they cost. It's just false economy imo.
 

retrogear

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While waiting for parts, I'm still running mine w/o the RIFA cap and my family hasn't complained about wifi troubles. The display looks fine. Besides, the transmitter would be the switchmode transformer running in the 100's of KHz and everything modern including HDTV broadcast in the UHF range and wifi is in the GHz range. Even with harmonics, it's not in the same ballpark.
 

Chuck(G)

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Theoretically, you don't need the MOVs that are sometimes placed across the AC line for surge protection in PSUs. I'd still replace them, since they cost so little.
 
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