Macintosh Plus keeps tripping RCD

[mpe]

I recently acquired a Macintosh Plus (version with the international 220V analog board - as I am in UK).

It seems to be working fine. However, there is a strange issue with it.

When switched off and connected to a wall socket (the switch on the back is off) it always after a couple of minutes keeps tripping RCD fuse in my house. So it looks like it is leaking current to ground somewhere.

It is not the power cable. I tried to visually inspect the analog board, measure input voltage and ground using a multimeter and did not find anything suspicious or obviously broken.

Any ideas?

 

[marcelv]

probable C33 and C36 these will be cracked after all the years of service and create a shortcut.

you can remove the capacitors, you can test the mac without them,

 

[mpe]

Thanks. C33 and C36. Is that on the original board? The only scheme I found is for the 120V board where this part is actually slightly different. Anyway, I guess these are two small line filter caps (4700 pico farad, Y class) just next to the power inlet. I will try to replace them.

 

[marcelv]

C33 and C36 are the numbers for the international board. these are the 4700 pf line filter caps

 

[techknight]

look for the yellow boxy caps if your board is different. they will have cracks. 

 

[mpe]

Replaced C33/C36 and the board seems to be fine now. Thanks!

These were relatively easy to replace. I even didn't have to take the board out. I am happy I didn't have to replace the bigger caps...

Originals don't look too good:

 

[Solvalou]

Necro time.

I'm having exactly the same problem. It tripped as I was trying to initialise an external SCSI drive for my Plus (thankfully I was only testing it at the time). But when rearming the RCD after the Mac Plus was switched off, it went off a couple of minutes later.

Scared the shit out of me.

Who would have imagined that something that is switched off would cause it to trip?

Trouble is I really don't like working with high voltage stuff, so I'm going to have to find someone fairly local for help.

Il get the components in the mean time I suppose.

Fun times!  :undecided:

Edit: Quick question; does it matter what material it is?

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F253399756065

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F273462730158

Are either of them suitable replacements? I would rather replace it with something as-good-as, if not better and by a trusted brand.