Macintosh 512k analog board replacement

[Apostrophe]

Hi,

The time is almost here to get my Macintosh 512k working again. Pretty soon I'll be able to afford a replacement analog board for it.

But I have several questions, and despite having searched online and here at the forums, I haven't found answers yet (I did read that classicmac2 PDF file. The questions I have here are the few that weren't answered by it), so here we go:

Please keep in mind that I'll be wearing gloves during the entire procedure.

1)

Also, verify that the machine is rated for your local line voltage.

How can I tell what voltage it's set for?

2) In this other Mac 128k/512k PDF file I found, it says that "Replacing only power/sweep may damage new power/sweep board. Replace power/sweep board, logic board, and internal drive, then turn on Macintosh." So I gather it's saying that replacing just the analog board may damage the new one. Is this really true? Here's the PDF file, and it's on page 21:

http://www.retrocomputing.net/info/siti/apple_repair/www.whoopis.com/computer_repair/Macintosh_128K_512K.pdf

3) This Mac has been sitting unplugged for a month; is CRT discharge necessary? If so, what's an easy way to do it if I don't have a discharge tool handy?

-Apostrophe

 

[tomlee59]

The warning in that pdf is a very general warning. It's saying this: "If the analog board died because other stuff connected to it misbehaved, then the new board is at risk of similar damage." It's certainly possible for this to be true, just as it's possible for a previously undetected comet to crash into your home. However true, neither is probable enough to constitute a source of concern.

The CRT's charge won't harm you, but it can surprise unpleasantly. A piece of wire will act perfectly fine as a "discharge tool." Assuming that the tube hasn't been removed, connect one end of the wire to the ground lead in the frame above the CRT (see pic in my doc), and stick the under end under the anode cup. That's it.

 

[Apostrophe]

Awesome! Thanks Tomlee!

-Apostrophe

 

[Mac128]

1) How can I tell what voltage it's set for?

3) This Mac has been sitting unplugged for a month; is CRT discharge necessary?

1) The voltage should be on the agency label on the back of the Mac. However if you suspect the analogue board has been replaced, THIS THREAD should help identify it.

2) Discharge is probably NOT necessary. Generally letting it sit for 24-48 hours is enough. But better safe than sorry.

 

[tomlee59]

Thanks to Mac128 for refreshing all of our memories on this, and for providing a link to Apple's own information on this topic. In the US, none of the classic Macs shipped with dual-voltage analog boards. Assuming that your source of analog boards is not too far from your home in Ohio, they should all be 110V units. If, by some chain of events, you end up with a 220V unit, you won't damage anything by operating it with 110V. But it also won't function, either.