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joshc

Macintosh Plus (originally 128K) International Analog board capacitors / components

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I have a 128K which was upgraded back in the day to a Plus. It has the 128K front and the Plus 1MB back case. Logic board and Analog board are Plus parts.

 

It powers on but has no video. I suspect some worn out components on the analog board.

 

Straight away upon inspection - the C1 capacitor is bulging badly at the top, and leaking at the bottom. So I've removed that, and now I'm finding it hard to find a replacement!

 

The capacitor says 35 V 3.9 uF (M) on it.

 

The analog board is part number 630-0108 - it's stamped with 'International'. (I'm in the UK...)

 

I checked this well-circulated list of components for the analog board, but it says C1 is 3.9µF 100V. However this list seems to be for U.S. analog boards only...

 

https://docs.google.com/spreadsheets/d/132RwzC8HM5ask-BdY_31txErOCwJDSkz099GY2XLpE0/edit?hl=en&hl=en#gid=0

 

So does the International version of the board use a lower voltage capacitor, or are they interchangeable ?

 

I also removed the two RIFA film capacitors, as they looked ready to explode and are badly cracked. These are marked RIFA 4700pF PME 271 Y 250V~SH . What can these be replaced with?

 

Photos attached if it helps.

 

Thanks in advance.

IMG_5172.JPG

IMG_5174.JPG

Edited by joshc

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Woops, I might have answered my own question with the paper capacitors...I am fairly certain these are the correct replacements. Unless anyone knows of a more robust component to replace them with?

 

https://uk.farnell.com/kemet/pme271y447mr30/cap-4700pf-20-paper-radial/dp/9717552?scope=partnumberlookahead&ost=PME271Y447MR30&searchref=searchlookahead&exaMfpn=true&ddkey=https%3Aen-GB%2FElement14_United_Kingdom%2Fw%2Fsearch

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Potential replacement for C1?

 

https://www.mouser.co.uk/ProductDetail/United-Chemi-Con/EKXE401ELL3R9MH15D?qs=sGAEpiMZZMvwFf0viD3Y3fHxNcSaiftwx%2B5cRnxFQPSqFS4oBxuzkQ%3D%3D

 

Seems like its OK to change to a higher voltage as I believe that's an upper limit? This is also 105 C vs the original 85 C rated one so should last a bit longer perhaps.

 

I'm still keen to hear from others here regarding what you've used for the C1 capacitor on your Plus analog board.

 

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I haven't actually done my Pluses yet, but I was planning to use a ~100V cap personally since that's what I have in my big drawer o' capacitors (I too am in the UK).  I don't think it matters unless the rated cap voltage is *stupidly far* above the voltage at point of use.

 

That said, I'm by no means an expert...

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