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How dangerous are RIFAs?

liamur

Active member
I've got a Mac Plus that appears to be stock (aside from 4MB of RAM) and I'm wondering about the RIFA caps. First of all, do I really need to replace them? I'm not adverse to soldering---the analog board probably has cracked joints anyway---but I don't like waiting for parts (and paying $10 shipping for $5 worth of caps). Also, I know that when the RIFAs go bad, they explode and make lots of smoke. How much of a threat is this to the wall supply, the computer, and/or me?

From what I've read on here and r/VintageApple, my current understanding is that it's okay to run with old RIFAs, but not ideal, and that when they explode, it's pretty nasty but harmless.
 

3lectr1cPPC

Well-known member
First of all, do I really need to replace them?
Replace? No. Remove? Yes. Just clip them out of the board, no fancy soldering needed. They will blow up at some point, and from what I've heard, RIFA smoke smells absolutely awful. It isn't dangerous when they blow, but that stuff stinks and probably isn't great for the lungs either. No hard in leaving them out, worst that could happen is that it trips the wall supply breaker, but I haven't ever heard of this actually happening. I'd replace them at some point, but at least get them out now.
 

Byrd

Well-known member
Check the RIFA caps for cracking - most will already have deep groove in them suggesting replacement, but you might be lucky. And yes, you need to replace these eventually otherwise the stink the fills your house - it won't give you many fans.
 

liamur

Active member
Ok, then. Thank you both. I'll check for capacitor cracks (I highly doubt they've been replaced), and if they're bad or old I'll desolder them completely. I want to go over the analog board anyway to check for and reflow cracked joints.

If I have a DigiKey order for another project, I'll grab some replacement RIFAs and solder them in.
 

Phipli

Well-known member
Cracks are a sign of age rather than imminent failure - they will have cracks. I've never replaced X and Y line filter caps unless they're already failed. Sorry to contradict.
 

cheesestraws

Well-known member
You should replace them. The machine will work without them, but you're introducing high frequency noise back into the power lines, which may have a deleterious effect on other devices, which may be your neighbour's rather than yours. They are protection devices in that they are protecting other devices from this one, not protecting this one from other devices.

This comes under the same heading as RF shielding. It is there for a reason, you should respect that.
 

3lectr1cPPC

Well-known member
Yeah, that's about what I've heard. Replacement not strictly necessary, but should be done just in case. Short term it should be fine but I'd agree that they should be replaced.
 

liamur

Active member
Well, fortune is on my side. It seems that somebody got to this analog board before I did and installed film caps in place of the RIFAs.
IMG_20221001_130130245_HDR.jpg
Picture for reference, see the red caps next to the small transformer and the blue/green/white toroid.
 

68kPlus

Well-known member
I replaced mine, as I couldn't bare with leaving the Plus and then one day the RIFAs explode and I'd have to open it up to clean things and remove the RIFAs. Easier to just replace them and get it over with.
Note: I had no experience doing this and it was all a learning experience, but I did it anyway and learned a lot!
 

Corgi

Well-known member
I have two SEs of unknown condition and I was about to plug them in and see if they work and then I remembered this thread. Do SE systems have RIFAs? I couldn't find a good answer other than this page that basically said "maybe" – without showing where to even look. Also, it's been trying for me to find what I am meant to replace them with. Is there a resource I should be looking at?

One is a standard SE, and the other is an SE FDHD, if that helps.
 
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