The original Macintosh desktop computer, initially released as the "Apple Macintosh" in 1984.

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Macintosh Plus Analog board keeps blowing its Fuss and Thermistor.

Hi I bought a Macintosh Plus from Canada ( I'm from Ireland) and plugged into my step-down converter then I flicked the switch on the back and I heard a really load pop, so I opened the machine the 2.5A tube fuse was blown ( black sot inside the tube) and the thermistor at R39 had blown in half. I checked over the Analog board and I cant seem to find any thing else damage besides the fuse and thermistor, so I order 10 Ohm 3A Power NTC Thermistors and I received them today (a month later) I have soldered the new thermistor in and the fuse is still blowing and the new thermistor looked to be slightly damaged at the tip of the leg. I'm mainly wondering if anyone has experienced this before and if so did they find a way to resolve it ?


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Hi kevinayres5, take more pics, of the affected area, there could be a short which keep blowing the components.


The bridge rectifier may be shorted. Desolder it and see that none of the pins are shorting to any others (typically all will short together when failed)


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The is probably the best place to go on this. I've used this guy on the Mac+ machines and he's good but slow (just like the machine):

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