So, I'm planning out a Mimeo build, and need to decide how much grounding to do, and where to connect everything up.
It looks like most people just use a 2-prong AC connector and mount everything on wood or plexi, so there's just a signal ground, no chassis ground to speak of, and no earth ground.
However, I'm thinking that's not the best bet, and proper grounding would be a good idea.
There's a few possibilities here, which could be combined as needed:
Connect motherboard power pin 6 directly to earth ground
Ground transformer cores
Mount everything on a conductive surface (with standoffs, obviously) - could set up ground loops, though, which would be Bad News(tm)
Thoughts?
You should join the retro-restore yahoo group. I put up a doc on what to do.
Disclaimer. You will be working with high voltage electricity and vintage components. I take no responsibility for the accuracy of the instructions or for any loss due to the use or misuse of the document.
Just submitted a membership request there, thanks for the tip.
For what it's worth, I've looked through the messages, files, and photos, and didn't see that document of yours - the only thing in the Apple-1 folder was Mike Willegal's 6502/Apple-1 cheat sheet.
What's the title, so I can better search for it?
Thanks,
Eric
I use a grounded receptacle and connect a 100K to 1Meg resistor between earth ground and the Apple 1 circuit ground. Since the Apple 1 board is isolated this prevents voltage buildup on the circuit board but prevents serious ground loops. I also earth ground the transformer shells so that a short cannot make them hot since they are usually exposed and could be a shock hazard. Cover all exposed 110V wiring to prevent shock and potential accidental shorts, this may seem obvious but some of the setups I have seen are accidents waiting to happen.
For power connection I use a power entry module Schurter DD11.0111.1110 with companion fuse holder 4301.1409. This provides a socket to use a standard PC power cable and a place for the fuse and spare fuse. These are in stock from Newark and Mouser.
wsander
My fault, I thought I uploaded it... It's there now... It includes the bleeder resistor that Wendell talks about (I got the idea from him originally).
One other comment. The operations manual shows the fuse on one side of AC input and the switch on the other. I recommend putting both the fuse and the switch on the "hot" side of the circuit. This will prevent a blown fuse from making the system appear off, when in fact the switch is on and the transformers are powered.
regards,
Mike W.
Yeah, I noticed that in the assembly guide. I'm guessing that Apple did it that way back then because of unpolarized plugs, and not knowing which would be hot or neutral?
I think I've got a pretty good idea of how I what to do the electrical system now. There'll be some slight personal touches I do that differ as far as component selection, but electrically, it'll basically be Wendell's design I think.