Class X capacitors go across the line. Class Y capacitors go from the line to ground.
You mean X in parallel and Y in series? I've not looked at the traces on the power board closely enough to know...
Don't substitute. The failure modes are different. Y2 has higher insulation breakdown voltages as well I understand to reduce risk of exposure.
The thing is you want the class X capacitors to pop the dielectric if there is a line transient. They will absorb the transient and heal; that's the point. You don't want the Y class ones doing that.
Sounds like it's most important to get the X cap right then? Since it's behaviour is so different than standard? Is 'Y' essentially a 'normal' cap?
I just ordered
3 * 0.22uF X2 metal poly and
5 * 1nf/1000pF Y2 metal poly. Yes I only need 1 and 2 respectively but I always overbuy...
So I will replace the big X2 with an X2,
but on my scope (and in the photo you posted), the 1000pf is
not marked X2. Nor are they marked RIFA as far as I can see. Just the Farad rating. I would be replacing these with the 1000pF 'Y' caps. At Bitsbox the 1000pf value was
only available in 'Y' or non-specific ceramic of various kinds. See the links in previous post for what exactly I bought.
Did I screw up? Do I need to find X2 caps at 1000pF? :/ - note again I cannot see any 'X2' on the 1000pF(s) - only the big 0.22uF.
Parts arrive tomorrow. Someone please tell me if I got the wrong bits so I can kick myself. Cheers!
~Atheus
P.S. I am still reluctant to do this due to my soldering experience... I may
sound like I know what I'm doing (the best way to succeed as an engineer I find!) but I've been in software for 10+ years and have hardly touched a soldering iron since university (apart from the last few weeks of course). I'll be putting a kit together this weekend though (one of those cheap Chinese ESR meters which are apparently not too bad) so I think if that works first time (well... say third time lol...) I'll have a go at the scope. Might practice some desoldering too... I really do not want to f**k this up and break an instrument I'm damn lucky worked in the first place!
/edit: looking again, I don't think my 0.22uF X2 is mains voltage rated. The 1000pF Y2 is (250V). This might be okay since Y2 goes power -> ground and X2 goes across in parallel... or I might have completely misread the caps and ordered the wrong parts. Yay.
One thing is for sure - there is no 1000pF/1nF X2 for sale on the Bitsbox site (though I see it on others so know it exists) so it can't be too common. I hope I did the right thing!