10 Apr
2025
10 Apr
'25
5:26 a.m.
On Thu, Apr 10, 2025 at 3:02 AM Fred Cisin via cctalk
<cctalk(a)classiccmp.org> wrote:
But Tony has already removed the lock. Either by
picking it to open the
case, or coming in through the back of the case. Locks on computer cases
offer extremely little security.
To make some reference to a classic computer here (:-)) the lock on
the P3800 only operates the switches. It does not anchor any part of
the case.
To get inside the machine you first remove the side panels (2
quarter-turn fasteners towards the top on each one, #2 Pozidriver to
undo them). Then remove the rear panel in the same way. The top is
retained by the rear panel, after removing the latter you slide the
top backwards to free it from the studs on the chassis and lift it
off. This reveals 2 thread-forming screws going through a bracket on
the top of the front panel. Loosen those (same #2 Pozidriver) and take
the front off.
You now have some normal dismantling to do to get the bezel round the
drives, drives, etc out to get better access to the switch unit. You
have to then disconnect its cables (one to a PCB on the back of said
bezel, one to the PSU backplane in the cardcage, one to the mains
relay board) and free them. Cut cable ties, etc. Take out the earth
wire screw and the 2 screws holding the switch assembly to the front
right chassis upright and pull the lot out.
With that on the bench, cut the 2 cable ties holding the cables down.
Take out the 4 (2 on some machines?) self tapping screws on the front.
The plastic housing with the switches and camshaft comes off. There's
then a large nut round the lock barrel on the back of the metal
bracket. Undo that, slide out the lock. There's a plastic spacer on
the lock that then slides off.
However, 4 pin/tumbler sets would make
it hard to turn on and off the machine without "breaking" into it.
And, the interlock (in/out for a different pin stack prevents anybody
without the key from turning it off. A wise move if there are college
administrators around.
Exactly. If you have unrestricted physical access to the machine (as I
obviously do in this case) the lock is not a problem. I can remove it
and turn the camshaft by hand. I can bypass the switches electrically
(it took me only a couple of minutes to work out what they do). I can
fit a replacement lock if I can find something suitable.
But if the machine is in use where others are around they are likely
to notice somebody taking it apart. Or attempting to pick the lock. If
it was just a knob then anyone could walk past and twiddle it without
being noticed.
-tony