Dyna Comp DCF 353 RIFA cap values

[croissantking]

I'm servicing a Dyna Comp DCF 353 and the two RIFA caps are missing:



I've searched for values for these on 68kmla and elsewhere, but have come up short.

Does the PSU need these to be there to operate?

And if so, does anyone know what values these would be?

 

[cheesestraws]

They are not strictly necessary to operate, but they will stop the computer injecting noise into the power lines and breaking your neighbours' power line network. It's a good thing to reinstall them.

If you don't get an answer by mon/tues (when I'm back home), poke me and I'll look in one of mine.

 

[GRudolf94]

Presumably 220nF and 470nF (a.k.a. 0.22uF and 0.47uF), X or Y rated, depending on how they're wired (Y if line to earth, X if line to line), rated at higher than line voltage (typically 270V if memory serves?). That's the general ballpark formula for line filter caps.

 

[croissantking]

Presumably 220nF and 470nF (a.k.a. 0.22uF and 0.47uF), X or Y rated, depending on how they're wired (Y if line to earth, X if line to line), rated at higher than line voltage (typically 270V if memory serves?). That's the general ballpark formula for line filter caps.

I have a photo now showing that C2 is 0.22uF. According to what you’re saying C1 should be 0.47uF.

 

[GRudolf94]

Additionally, we can juuuust see C2 is X2-rated. That 250V rating is cutting it too close for comfort on an UK line voltage.

Care to get us a pic of the underside of the board? That should allow for deducing how C1 is wired.

 

[croissantking]

Additionally, we can juuuust see C2 is X2-rated. That 250V rating is cutting it too close for comfort on an UK line voltage.

Care to get us a pic of the underside of the board? That should allow for deducing how C1 is wired.

 

[GRudolf94]

Based on these guesschematics, they're both connected across the line, and as such should be rated X2 (or, even better, X).

 

[croissantking]

Based on these guesschematics

I've sourced these parts at Mouser, what do you think?

Kemet PME271 275V 0.22uF 10% LS=22.5mm

https://mou.sr/3uvzDdK

Kemet PME271 275V 0.47uF 10% LS=25.4mm

https://mou.sr/49uz0zL

The only problem is the 0.47uF cap is massive (15mm wide) and it will not fit. Is it possible that both caps were actually 0.22uF?

 

[GRudolf94]

Yes, it's quite possible. I find the lack of Y caps rather odd, but I don't see where any could go.

 

[croissantking]

If you don't get an answer by mon/tues (when I'm back home), poke me and I'll look in one of mine.

I haven’t been able to find out what value C1 should be. If you wouldn’t mind checking for me, that’d be a big help.

 

[cheesestraws]

Turns out mine all have Astec PSUs. Sorry :-( I thought I had a dynacomp.

 

[croissantking]

I’m going to put in both 0.22uF caps, then, and fingers crossed.

 

[dougg3]

I know I'm late here, but I figured I'd post this for completeness. I'm in the process of attempting to fix one of these Dyna Comps. Several of the parts have icky green corrosion so it might not be a fun repair, but I can confirm that C2 is X2 and 0.22uF +/- 10%. If I peel that piece of paper up a bit, I can also see that it's marked as KNB1530.

C1 is harder to see because of L1 being completely in the way, but I can also make out that it's identical, also 0.22uF and X2. Here are pictures.