Apple IIe DynaComp power supply - capacitor identification and repair advice needed

[yggg]

Hi everyone,

My Apple IIe power supply unit, Dyna Comp variant from 1984, had a cap failure recently, Kemet/RIFA PME271M EMI/RF X2 ones to be exact.

As I went in to replace those with new ones, I noticed that a couple of capacitors nearby seemed chipped or cracked and I can't readily identify them *see attached pics*. They seem to be Mullard ones after a quick search on Google, but I'm not really sure... Any ideas on what I could replace these with?

Also, while I'm at it, should I consider recapping all the electrolytic ones? They are all original and ~30 years old, but none seem to be leaking or bulging right now. Any ideas or thoughts?

[japlytic]

Re: Apple IIe DynaComp power supply - capacitor identification and repair advice need

Welcome, yggg!
The first capacitor: Brown (1) Black (0) Yellow (x10000) White (10%) Red (250V DC) - 0.1uF 250VDC 10%
The second capacitor: Brown (1) Black (0) Green (x100000) White (10%) Red (250V DC) - 1uF 250VDC 10%

You can use 400V or 600/630V units if you are still unsure.

As I said elsewhere, the Rifa/Miniprint X-class units are known to be unreliable.

[yggg]

Re: Apple IIe DynaComp power supply - capacitor identification and repair advice need

japlytic, I really appreciate it!

I wasn't sure if the red color at the bottom of the caps meant a voltage rating of 250 VDC or VAC. But you're right, it is VDC and I could always go with a higher voltage rating. I plan to use Vishay MKT368 caps to replace these two as I think I found some where the lead spacing is fairly close.

Still, any thoughts on whether I should recap the electrolytic ones? There are about a dozen of those and I could save by ordering new ones for those as well.

Thanks again!

[sam_sam_sam]

Re: Apple IIe DynaComp power supply - capacitor identification and repair advice need

If were up to me I just recap it

[PeteS in CA]

Re: Apple IIe DynaComp power supply - capacitor identification and repair advice need

I wouldn't think of Rifa PME271 (I'm pretty sure the "M" refers to the 20% tolerance) X-caps that failed after 30 years of whatever line surges they absorbed there in North Carolina as poor reliability. Quite the opposite! Pretty much any brand and dielectric type will fail after lots of years and surges as an X-cap.

Anyway, the lytics ... replacing 30YO O/P capacitors would probably be a good idea, though you should be careful not to get parts whose impedance is too low. That precaution sounds odd, but the feedback control circuit is designed for O/P caps with ESR and ESL in a certain range. Modern ultra-low impedance parts might cause stability problems. I would recommend Nichicon PJ or UCC LXV, if you can find them; or Nichicon PW or UCC LXZ as second choices.