AC power on front panels

Richard A. Cini rcini at
Sat Jan 14 00:15:07 CST 2006

Interestingly, there is no fuse holder at that location (bridged with a
jumper). Instead, there is a standard 1-1/4" glass fuse holder in the back
panel. Certain spots of the power supply board I've glued-over with
insulating plastic (salvaged from the HV section of various power supplies
over the years).

Very bad design indeed. The pads at the top are very close to the metal cage
and the HV traces on the power supply board are uninsulated.

-----Original Message-----
From: cctalk-bounces at [mailto:cctalk-bounces at]
On Behalf Of William Maddox
Sent: Saturday, January 14, 2006 12:21 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: AC power on front panels

I don't think there is anything intrinsically unsafe
about the switch itself, which is rated for line
voltage and likely UL approved.  The idiocy of the
IMSAI design is that the switch is connected via PC
traces to solder pads at the top edge of the board
where the wiring to the power supply attaches -- live
line voltage exposed at a location that just invites
contact while one is otherwise careful to avoid the
power-supply internals. I've seen people put a few
strips of electrician's tape over the pads to insulate
them, though a fold of fishpaper and hot-glue might be
less likely to fall off with age (??).  Another piece
of bad design is the bare metal fuse clip that is so
close to the edge of the power supply PC board that I
would be concerned about the possibility of contact
with the case cover, e.g., if the case was
sufficiently deformed.  Another fishpaper might be a
good idea there.


More information about the cctalk mailing list