[SlideCube] B&H Operation

John H. DuBois III spcecdt@armory.com
Sun, 19 Jan 2003 19:14:49 -0800

On Sun, Jan 19, 2003 at 01:15:25PM -0500, Greg wrote:
> I have a Bell & Howell slide cube projector (CP 40) that has a square button
> that is supposed to advance the slide turntable.  My problem is that the
> turntable only turns as long as I have the button depressed.

Slide cube projectors use a pin-and-slot mechanism to continue the advance
until the next viewing position is reached.  When you press the advance switch,
a solenoid pulls a pin out of a slot on the turntable.  The pin itself is
connected to a switch that parallels the advance switch, so as long as it is
out of the slot the advance continues.  A spring tries to pull the pin back
into the slot, but as soon as the turntable has advanced the slightest amount,
it can't go back into the slot it was in, so if you let go of the advance
switch at that point the turntable will continue advancing until the next slot
is reached, which corresponds to the next viewing position.  This linkage also
extends to the shutter, so the projector is blacked out during the slide

While the pin is in the slot the projector can't advance, and when it's out of
the slot you can't see anything since the shutter is closed.  Since you are
able to advance the projector and see a projected image, the basic mechanism
(solenoid, spring, etc.) is obviously working.  My guess is that the switch
connected to the pin linkage is broken, or one of the wires that connect the
switch to the advance motor is broken.  Fixing your problem may be just a
matter of reconnecting a wire or bending some switch contacts so that they
close properly when the pin moves, or it might be that you will need to replace
the entire switch.  My recollection is that the switch consists of some springy
contacts, not a standard switch, so if the switch isn't repairable you
might have to build a replacement.  

John DuBois  spcecdt@armory.com.  KC6QKZ/AE  http://www.armory.com./~spcecdt/