Mains Suppression Capacitors - Page 1
Forum section: electronics / projects

author: NivagSwerdna
author_rank: Super Contributor
timestamp: November 18, 2020, 08:36:32 pm
content: 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?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 18, 2020, 08:45:01 pm
content: The calculation is as follows:Capacitance: 1.0 * original capacitance +/- 20%Voltage: >= 1.0 * original voltage ratingAcross-the-line type: X2 or betterLine-to-ground type: Y1 or betterTim

author: NivagSwerdna
author_rank: Super Contributor
timestamp: November 18, 2020, 09:05:12 pm
content: 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?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 18, 2020, 09:12:43 pm
content: 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.htmlIf 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

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 18, 2020, 10:00:01 pm
content: 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).

author: NivagSwerdna
author_rank: Super Contributor
timestamp: November 20, 2020, 08:13:48 pm
content: 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?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 20, 2020, 08:51:21 pm
content: 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

author: NivagSwerdna
author_rank: Super Contributor
timestamp: November 20, 2020, 08:56:21 pm
content: Quote from: T3sl4co1l on November 20, 2020, 08:51:21 pmSo it's unlikely to be of an exploding 'RIFA' type then?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: November 20, 2020, 08:59:56 pm
content: 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=ukIt was the "These too have a tendency to go bang in their old age" that worried meAnd 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?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: November 21, 2020, 09:54:23 am
content: 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 EMIReplace with a more modern alternative... these seem to exist in vacuum cleaners and dishwashers so probably could use one of thoseReplace the socket with this filtering built inI think I am going to go with the last option... e.g.