Daftpunkerz started following Fixing Macintosh Plus Analog board keep's blowing its fuse.
Daftpunkerz posted a topic in Compact MacHi everyone So I have something that wouldn't really be considered unusual a very sick Macintosh Plus I have yet to see it boot or do anything else than try and kill it's self. I bought this Macintosh Plus off a Friend who had more money than sense and he bought it from Canada and had shipped here to Ireland, sadly he thought it would be a simple plug and play and he never heard of a step down converter. when he plugged straight in the Irish 250V socked it blow the crap out of it and he said it just popped. So 2 months later he offered it to me because he bought a UK one instead and I got it for a tidy €40 which is cheap on this side of the pond even for a broken one. On opening the machine I noticed 2 things the Fuse on F1 was blown looked burn't out and the thermistor on R39 was broken in half. so I replaced both of those think this may resolve the issue but both the Fuse and the thermistor blow again with spark's coming form the new thermistor and I new I did buy the right one but when I took a second look at the board both the Rectifier and Diode on CR20 and CR21 had heat damage on there legs, I have also replaced these and this fixed one issue the Thermistor no longer sparks but the fuse is still blowing when I plug it in. Yes I am using a step-down converter which I have tested that output's 117V to be exact so it should be safe. There is one more thing I can think of which is the Fuse trace lead's directly to 3 spick suppressing capacitor's the first one is a large one which I have just removed to test with a Multimeter (which I know isn't exactly accurate but my ESR meter is broken and waiting for a new one in the mail) and it has showing no signs of life on capacitance on the multimeter so I'm guessing this could be dead and causing the fuse to blow I'm not use it's only 0,1uf 250V this located on C38 and the other 2 are C33 and C37 are these known to case a fuse to blow ?. I would be very grateful for some in put on this analog board I have wanted a Macintosh Plus since my Grandad would let me play on his just a bit of nostalgia, also this Analog is starting to get expensive to repair and I'll need a solution soon before I've replaced everything on the board haha.