Heat and noice concerns

[sje]

If I recall correctly, MITS offered the Altair 680 with an optional five inch box fan to be mounted on the back plate. For such an exhaust fan to work properly, there was a need for side vents in the case.

A big difference between then and now is the substitution of smaller and more efficient power supplies. The old style linear supplies used a lot of energy taking 60 Hz 120 VAC and beating it into submission (as we used to say) and all that energy wound up as heat inside the case. So the vents were useful with dumping that heat, and a fan was a good idea if there were any expansion cards in the machine.

If there aren't going to be any expansion cards in a replica 680, then I wouldn't be concerned about the lack of vents or a fan. However, please note that unlke the 8800, the 680 had its expansion cards mounted horizontally. And that tends to traps heat due to lack of convection. Would that be a problem? Maybe not, but consider this: would MITS have paid extra for any feature (like vents) if the feature wasn't truly needed?

[marty]

Hi;
I saw in an old Mits Computer News, that enough power was sometimes a problem and they showed mounting a transformer on the outside, like one of you pictures shows. I didn't read the article, so I don't know the particulars. Thanks Marty

[frotz]

I have a vintage IMSAI 8080 that has transformers mounted on the outside like that.