I'm building a Mimeo 1 and have just finished building the board, and just built my power entry module.
I tested the PEM by itself (not connected to the Mimeo 1), and the leads coming off the transformers looked good. I think I was getting 11.5V AC on one of the transformers, and 32V AC on the other.
When I plugged it in on the Mimeo 1, the fuse made a humming sound for about 1-2 seconds then it stopped. I checked the voltages, and nothing now. I checked the fuse and it had blown (darkened but not actually broken). The fuse I used is a 3AG 250V 0.5A slo-blo fuse as per the Apple 1 schematics. I used an IEC connector on my PEM, and connected "live" to my on-off-switch, to the fuse, to the transformers (in parallel to each other). I connected the other line from the transformers to the "neutral" lead of the IEC plug.
I tested it again with another fuse, and same thing, it blew in 1-2 seconds - this time I noticed a small flash at the fuse.
I unplugged the PEM from the Mimeo 1, and installed a new fuse, and tested again, and the voltages look good coming out of it.
So in building the Mimeo 1, I took special care with everything. I checked continuity along the way and no issues. I solder everything under magnification, and visually inspect each joint as I do it. I've build one other homebrew computer (N8VEM), with no issues, and have build numerous other arduino projects. The only issue I had was when checking continuity was checking the LM323K. When testing the "input" to the "can" (actually to the screws on the underside of the board), my fluke VMM signaled a connection one way, but not on the same test point with leads switched. I turned it to ohms, and measured the following:
1) input to CAN: 1.3 M-ohms (or 1,300,000 ohms)
2) input to output: 1.3 M-ohms (or 1,300,000 ohms)
3) output to CAN: 1.1 K-ohms (or 1,100 ohms)
I can post a picture of my board and PEM.
Does anyone see anything that looks amiss?
I thought the 0.5A fuse was a bit small, but if that's in the Apple 1 schematic specs, then I guess it works.
Anyone have any specific areas to look for problems?
Thanks for any suggestions.
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