Dilbert Electronic Candy Dispenser Troubleshooting & Repair Videos for Engineers
My daughter, Sally, recently bought me a Dilbert Electronic
Candy Dispenser at a second-hand store. We soon learned the reason it was there and not dispensing candy
electronically on someone's desk.
When I loaded in a fresh set of batteries and pressed Dilbert's
computer mouse, nothing happened. I whipped out the DMM and measured the voltage at the two AA batteries
as 3.2 V with the switch open, and about 2 V with the switch closed. The system was getting voltage
and drawing current, but nothing was happening. I disassembled the contraption (no easy task), and assessed the
situation. The cam-operated shutoff switch was crammed against a stop, but it was not apparent why.
I then pried out the little DC motor and verified that voltage was getting to the motor. Having toyed
around with many similar motors as a kid, and noting that basically nothing has changed over the years,
I confidently unbent the two case retaining tabs and pulled the rotor assembly out from the stator magnets.
The key to getting it apart is removing the CPU front cover beneath the computer monitor.
I used a thin metal 6" engineering ruler (scale). The cover snaps in on each side with a little locking
tab. It will take a lot of force to pry the tabs out of the holes, but I have done it at least three
times with no damage to the tabs or the mating holes.
Be sure to note the placement of all the
gears and cams as you disassemble everything since the timing of the electrical switch is dependent
on getting it back together correctly.
were carbon deposits all over the brushes (2) and commutators (3), along with some poorly applied grease
that was supposed to be at the rear rotor support (not on the brushes). A little MEK on a Q-tip took
care of the misplaced grease, and then some 600 grit sandpaper on the brushes and commutators took care
of the carbon deposits. The motor was reassembled and then fired up while still outside the dispenser
reinstalling the motor and aligning its gear with the main dispenser gear, I pressed the start button
and it immediately started to run and then stall. I hurriedly removed one of the AA cells to prevent
damage; it is not possible to put the batteries in backwards. Upon close examination of the situation,
it became obvious that the entire gearworks was running backwards, causing the cam-operated shutoff
switch to get jammed into the cam rather than ride over the top of it. A quick reversal of the two wires
at the battery box rectified (literally) the problem; soldering required.
Everything else was cleaned (remember that it was second-hand) and reassembled. The
video below shows the results.
This collection of video and a few audio files represents files that have been featured on the RF Cafe homepage. Every week or so a new file
is added that should be of interest to RF Cafe visitors.
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB.
Its primary purpose was to provide me with ready access to commonly needed formulas and reference
material while performing my work as an RF system and circuit design engineer. The Internet
was still largely an unknown entity at the time and not much was available in the form of
All trademarks, copyrights, patents, and other rights of ownership to images and text used
on the RF Cafe website are hereby acknowledged.