Figure 1-43.Zeroing a synchro using a synchro tester.
2. Set the unit whose position the TX or CX transmits accurately on zero or on its reference
position. In the case of the TR, set its rotor to zero or to its reference position.
3. Turn the stator of the synchro being zeroed until the synchro tester dial reads 0º. The synchro is
now approximately on electrically zero.
4. Momentarily short S1 to S3 as shown. If the synchro tester dial moves when S1 is shorted to S3,
the synchro is not zeroed. Check the tester dial to ensure it has not slipped. If the tester dial has
not slipped, move the synchro stator until there is no movement when S1 and S3 are shorted. This
is the electrical zero position of the synchro being aligned.
Q-68. What method of zeroing a synchro is perhaps the fastest but NOT necessarily the most accurate?
Q-69. What restrictions are placed on the use of the electrical lock method?
Q-70. When you zero a synchro with a synchro tester, what is indicated by a jump in the synchro tester's
dial when the S1 and S3 leads are momentarily shorted?
TROUBLESHOOTING SYNCHRO SYSTEMS
One of your duties in the Navy is to keep the synchro systems in your equipment in good working
order. Therefore, it is essential that you become familiar with the details of synchro maintenance and
First, let's consider some of the more common problem areas you should avoid when working with
synchros. As with any piece of electrical or electronic equipment, if it worksleave it alone. Do not
attempt to zero a synchro system that is already zeroed just because you want to practice. More often than
not, the system will end up more out of alignment than it was before you attempted to rezero it. Do not
attempt to take a synchro apart, even if it is defective. A synchro is a piece of precision equipment that
requires special equipment and techniques for disassembly. Disassembly should be done only by qualified
technicians in authorized repair shops. A synchro, unlike an electric motor, does not require periodic
lubrication. Therefore, never attempt to lubricate a synchro. Synchros also require careful handling. Never
force a synchro into place, never use pliers on the threaded shaft, and never force a gear or dial onto the
shaft. Finally, never connect equipment that is not related to the synchro system to the primary excitation
bus. This will cause the system to show all the symptoms of a shorted rotor when the equipment is turned
on; but, the system will check out good when the equipment is off.