Macintosh Plus 120V to 230V conversion?

[mitchW]

I recently got a nice condition Macintosh Plus with one major problem: the previous owner got it from USA and therefore it was a 117V unit. Which he plugged into the 230V mains that we have here.

He said that the machine even started up and ran for a few seconds, then it died with some smoke.

I did a quick check on the analog board and the fuse is blown and also one of the two 200uF 250V caps is bulging. It is of course a 120V analog board. So perhaps there is not much damage after all.

As I don't really have a 230/115V step down transformer yet, I thought if someone figured out if it is possible to wire the 120V US board to accept the 230V? On the schematics, for the 120V analog board, there is 120VAC directly rectified to get the 170V DC, which differs to modern style SMPS where they use the rectifier as the voltage doubler on the 120VAC. 

I do have a broken 230V international 128/512K AB which I never got to fix, as I don't have proper schematics. As far as I searched, there are only available for 120V version. This one has few bad resistors on the primary, but it might also have other issues.

 

[bibilit]

The "International" Analog Board can be easily converted to 250V or left to 120V US, not the US "only"one.

 

[mitchW]

Yes, that is absolutely correct. The International version has a jumper that needs to be added and that switches it from 120V to 240V.

But, I thought that there might be a way to modify the 120V only version to work on 230V. Maybe change the rectifier diodes, change the capacitors to 400V or change them with higher values and wire them in series..?

If anyone has schematics for the International Analog Board version, I would be glad to get them.

Perhaps they only made a few changes to the primary side, and these changes could be easily done to the 120V unit. Anyways, even if not for that, I would need the schematics to repair my spare 230V International analog board.