Macintosh II PSU RIFA Cap Class? (ASTEC AA13780)

[BeniD82]

Hi There,

Currently working on restoring a Macintosh II system and would need some help with identification of some RIFA caps that are on the PSU. There are three 0.1 uF caps that are of the type that like to burn up. These have not cracked yet thankfully but I don't really want to push my luck. Unfortunately there's nothing that indicates whether those are X or Y type safety caps. Haven't really been able to find any thing about them online either unfortunately. There is also a larger 0.022 uF RIFA near the transformer and that one's clearly noted as a Y cap (which has completely cracked across its entire length so glad I didn't turn the PSU on before checking). Pics of the caps in question have been attached. Appreciate any input, thanks!

 

[Elemenoh]

I'll take a shot at answering but get a second source since I'm not an expert and safety is a factor.

An X capacitor is meant to be used line-to-line (i.e. between live and neutral) and is designed to fail short. If one fails, your fuse or circuit breaker would pop, preventing risk of shock.

A Y capacitor is meant to be used line-to-ground (i.e. between neutral and ground) and is designed to fail open. If one fails, the filtering will be compromised but there won't be a risk of shock.

That being said, what you have there is a 'precision capacitor' not an X or Y rated 'interference suppressor capacitor'. But I'm not familiar of why one would be chosen over the other for this application.

The data sheet for this specific cap is below. I think you'd be fine to replace it with a similarly rated polyester film capacitor. Just check the specs and make sure you get one with the right lead spacing. And again, getting a second opinion from someone who knows what they're talking about would be good. Perhaps cross-post to some place like eevblog forums.

 

[BeniD82]

Hi Elemenoh!

Not sure what dark crevasses of the internet you were able to pull the data sheet out from, but that was exactly what I was looking for. Spent a fair amount of time that evening looking for that specific piece of information but could not find anything, so clearly you're way better at sleuthing than I am, thank you so much for posting that!

From what I was able to gather, general consensus seems that metallized paper type caps, such as that PHE 280 one, can be replaced with equivalent modern metallized polyester or polypropylene (PP) versions without issue. Safety caps should only be replaced with a safety cap that has the same rating/class as the component that is being replaced (no issues with them using a more modern material). So your feedback pretty much was on point.

Seems if the cap were used for filtering on audio gear, with PP being a different material, it could impact audio quality, which for our intended use here wouldn't be an issue since we're not dealing with analogue audio. I ended up using PP film caps in place of the PHE 280 and replaced my blown safety cap with a modern equivalent with the same safety class/rating. Been running solid so far, no electrocutions or magic smoke.

Appreciate your help and feedback!

 

[Elemenoh]

Not sure what dark crevasses of the internet you were able to pull the data sheet out from, but that was exactly what I was looking for. Spent a fair amount of time that evening looking for that specific piece of information but could not find anything, so clearly you're way better at sleuthing than I am, thank you so much for posting that!

I found it on Archive.org by doing a text search