Mains Suppression Capacitors

[NivagSwerdna]

I have just bought a 1980s vintage disk drive (Commodore 8050) and looking at the various videos on YouTube it suggests that if I plug it in I should expect smoke and fireworks from the Filter Suppression capacitor.... which I assumes means a RIFA type AC suppression capacitor.

I would ideally like to avoid the excitement and smoke induced by this soon to be failure...

How would I determine a suitable MODERN replacement?  How does the math work in respect of calculating size requirement?

[T3sl4co1l]

The calculation is as follows:
Capacitance: 1.0 * original capacitance +/- 20%
Voltage: >= 1.0 * original voltage rating
Across-the-line type: X2 or better
Line-to-ground type: Y1 or better

Tim

[NivagSwerdna]

OK... I'll have to dig and extract the old one first then.

I like the 1.00000 x calculation... that works for me.

I assume the original designer would have been taking the inductance of the primary side of the transformer into account?

[T3sl4co1l]

Wait, it doesn't even show any. What the hell do you have?
http://www.devili.iki.fi/Computers/Commodore/8050/Service_Manual/page_28.html

If you mean inside the connector, just replace the whole thing if you need to be sure.  They're cheap and plentiful, and likely something new still fits.

Tim

[Vovk_Z]

Any modern X2 cap will be good replace for old RIFA X2.I use even Chinese ones a lot (I am sure they will last at least 30 years, and I don't demand more).

[NivagSwerdna]

The Schematic Linked above is what I am working with I think...

So I opened her up and see...



The Markings suggest 0.1uF + 2x2500pF XY... and it has four(?) wires...  must be some combo job?

[T3sl4co1l]

That doesn't seem to correspond to the schematic, at least of that revision.

Anyway, those filter modules aren't uncommon, you're welcome to replace it if you like but I wouldn't bother, just test it (measure DCR H-H and N-N, and high resistance (capacitance) H-N and H/N-case).

Tim

[NivagSwerdna]

Anyway, those filter modules aren't uncommon, you're welcome to replace it if you like but I wouldn't bother, just test it (measure DCR H-H and N-N, and high resistance (capacitance) H-N and H/N-case).

So it's unlikely to be of an exploding 'RIFA' type then?

[NivagSwerdna]

I also found this now deleted but cached page...

http://webcache.googleusercontent.com/search?q=cache:98QpoDdY2ccJ:blog.tynemouthsoftware.co.uk/2015/08/exploding-commodore-pet-mains-filters.html+&cd=4&hl=en&ct=clnk&gl=uk

It was the "These too have a tendency to go bang in their old age" that worried me

And now looking at my photos... I can see it actually reads... 0.1uF+2x2500pF XY + 2x100uH 250V 2A... so it really is a combo thing.  Maybe I'll just disconnect it as per the page above?

[NivagSwerdna]

This investigation has opened a whole area of devices I was previously unaware of....

I seem to have three options...

• Just remove it (to avoid the smoke and bang) and not worry about the EMI
• Replace with a more modern alternative... these seem to exist in vacuum cleaners and dishwashers so probably could use one of those
• Replace the socket with this filtering built in

I think I am going to go with the last option... e.g.