Last month I wanted to use my good old Cobra Robot for a new hobby project.
I hadn´t used the robot for some months. When starting the control unit I noticed a smell like burnt electronics.
However, all functions of the robot still seemed to be working. But for safety reasons, it seemed advisable not to use the device.
Because my knowledge in electronics is limited I needed some help to find out what the exact problem was and how to repair it.
Fortunately, I had practical help of my good friend Jens and remote email support from the german cobra-robot guru Bernd Barnewald.
The first step was to check all voltages and fuses. All voltages seemed to be normal and stable, all fuses intact.
So all circuit boards had to be checked.
After some search we found a exploded buffer capacitor.
Jens said, these capacitors are well known problems: In the 1980s, the chemical quality of this type of capacitors was not as perfect as it is today.