Cromemco Z2 and Electrical Safety

Jay Jaeger cube1 at charter.net
Mon Dec 26 09:31:49 CST 2005


I am restoring a Cromemco Z2D and have spotted a couple of electrical 
safety issues.

The machine was set up and the instructions were set up to fuse the 
*Neutral* rather than Hot.  I believe this is very bad, because if a fault 
develops (say, a ground fault from hot to ground) you want that fuse to 
blow so as not to start a fire.  (If the neutral is fused, even if the fuse 
blows, a hot to ground fault still has a current path thru the ground).  As 
the machine was shipped, and as the instructions were set up, they had the 
AC hot coming in on the wrong side, such that neutral is fused, rather than 
hot.

What happened was that they (Cromemco) had the Hot coming from the AC input 
connected to their White wire, which was not fused.   And the Neutral 
coming from the AC input was connected to their Black wire, which was 
fused.  Also, the way they had it set up, the neutral wire connects to some 
*GREEN* wires on the transformer, which is very misleading.  (Worse yet, if 
you fix the aforementioned problem by reversing the leads on the input 
filter, you end up with HOT on those green wires.

And it wasn't just this unit.  The instructions and diagrams in the manual 
have it wrong.  (The schematic is non-committal -- it doesn't identify hot 
and neutral, just colors on the output side of the line filter).

What a bunch a maroons.....

---	
Jay R. Jaeger					The Computer Collection
cube1 at charter.net




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