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Up to this point we have discussed only the individual sections of the electron tube power supply. In
the next section, we will discuss the techniques of troubleshooting these individual sections and the total
power supply.
Q41. What is the purpose of the amperite regulator?
Q42. As the tube filaments in the load heat up, will the circuit current increase or decrease?
TROUBLESHOOTING POWER SUPPLIES
Whenever you work with electricity, you must follow all the appropriate safety precautions. In the
front of all electronic technical manuals, you will always find a section on safety precautions. You should
also find posted on each piece of equipment a sign listing the specific precautions for that equipment. One
hazardous area that is sometimes overlooked, especially on board ship, is grounding of equipment. By
grounding the return side of the power transformer to the metal chassis, manufacturers can wire the
cathodes of the tubes in both the power supply and the load being supplied by the power supply directly
to the metal chassis. This eliminates the necessity of wiring each tube directly to the return side of the
transformer, saving wire, and reducing the cost of building the equipment. While this solves one of the
problems of the manufacturer, it creates a problem for you, the technician. Unless the chassis is physically
grounded to the ship's ground (the hull), the chassis can be charged (or can float) several hundred volts
above ship's ground. If you come in contact with the metal chassis at the same time you are in contact
with the ship's hull, the current from the chassis can use your body as a low resistance path back to the
ship's ac generators. At best this can be an unpleasant experience; at worst it can be fatal. For this reason
Navy electronic equipment is always grounded to the ship's hull, and approved rubber mats are required
in all spaces where electronic equipment is present. Therefore, before you start to work on any electronic
or electrical equipment ALWAYS ENSURE THAT THE EQUIPMENT AND ANY TEST EQUIPMENT
YOU ARE USING IS PROPERLY GROUNDED AND THAT THE RUBBER MAT YOU ARE
STANDING ON IS IN GOOD CONDITION. As long as you follow these simple rules, you should be
able to avoid the possibility of becoming an electrical conductor.
TESTING
There are two widely used checks in testing electronic equipment. The first is the VISUAL
CHECK. Do not underestimate the importance of this check. Many technicians find defects right away
simply by looking for them. A visual check does not take long; in fact you should be able to see the
problem in about 2 minutes if it is the kind of problem that can be seen. You should learn the following
procedure. You will find yourself using it quite often, as it is good not only for power supplies but also
for any other type of electronic equipment you may be troubleshooting.
1. BEFORE YOU PLUG IN THE EQUIPMENT, LOOK FOR:
a. LOOSE TUBES—A tube that is not properly seated in its socket may not be making proper
contact with the rest of the circuit. It may very well be the source of your problem. Push the
tube completely into place.
b. SHORTS—Examine any terminal or connection that is close to the chassis or to any other
terminal for the possibility of a short. A short in any part of the power supply can cause
considerable damage. Look for and remove any stray drops of solder, bits of wire, nuts, or
screws. It sometimes helps to shake the chassis and listen for any tell-tale rattles. Remember
to correct any problem that may cause a short circuit. If it is not causing trouble now, it may
cause problems in the future.
