14 Jan
2006
14 Jan
'06
11:53 a.m.
All:
I'm playing around with my relatively new IMSAI and I was
pondering the following. The unit is constructed with the front panel power
switch unconnected and the corresponding terminals on the power supply board
jumpered together. There is a mains switch on the rear panel which takes the
place of the front panel switch.
While for safety reasons I cannot disagree with the approach -
it's plain stupid to put uninsulated mains voltage in a low-voltage area
I would agree.... That is asking to either come into contact with some
signal line (and blow chips all over the place) or you (and blow you all
over the place).
(and unpassable by UL evaluators I'm sure) - it
detracts a bit from its use
because you have to reach behind the unit to turn it on.
Has anyone come up with an elegant solution to being able to use
the front panel power switch while keeping it safe? I was toying with some
sort of low-voltage circuit (small LV transformer and relay, with the front
That's how DEC did it in some of the PDPs. A little transformer energised
all the time with a rectifier and smoothing capacitor which suppled the
voltage to operate a relay. DEC, of course, added circuity to allow for
remote power on, emergency shutdown (if the machine overheated), etc. We
had a discussion of the DEC power bus a week or so back.
panel switch in the loop on the coil side). Another
idea I had was to hot
glue a dielectric insulator board (that gray cardboard kind of stuff) over
the parts of the front panel that would be exposed.
This has the advantage of being closer to the original design (in that
the machine is electrically unchanged).
But I would go for the relay solution if it was my machine. It would be
safer I think (both to you and the machine).
-tony