2.
Trouble diagnosis. To diagnose troubles in a tape machine, you need to remember that a
combination of features can cause trouble. In a tape machine, you have a group of mechanical functions
as well as the various electrical circuits. Indications obtained from the electrical circuits point to most of
the troubles. These troubles may or may not be in the mechanical mechanism, but you must "read
through" the troubles to make your diagnosis. Once you detect a malfunction, you should look
immediately for the cause; however, a quick mental reference to the most common troubles and their
causes should speed your diagnosis.
3.
Variations of speed. Identifying "wow" and "flutter." The word "wow" is used to describe a
slow variation of speed, whereas, "flutter" describes a fast variation of speed. If the speed is consistently
wrong, the audio signal is off pitch. This condition is easily recognized with music but can be difficult
to determine with spoken words.
a. A "wow" could be caused by certain faults, such as a slipping belt, a lack of proper pressure
on the capstan motor winding damage, or an uneven tape surface.
b. A "flutter," which is much faster, would more likely be caused by something moving at a
higher speed. The capstan could be out of round and give this fault with every revolution.
c. Sometimes a tape guide can cause a bouncing action to be repeated at a fast rate. A signal
which is consistently off pitch or key may be caused by insufficient or excessive drag on the tape as it
passes through the transport system. This could be incorrect action of the supply reel, the pressure pads,
tape guides, or improper threading of the machine.
4.
Weak outputs. If you have an indication that the output seems to be weak, or that it is not giving
full response to the higher frequencies, you might look for electrical trouble. Pause for a moment and
think what would happen if you have only a portion of a track passing over a head. We know that the
strength of the output signal is relative to the magnetic influx recorded on the tape and the tape speed.
You already know that head wear causes a drop in high-frequency response, but if the track or head is
misaligned, you will not get full benefit from the recorded signal. You may need to check head wear,
track, and head alignment. If these seem to be correct, then check the circuit components. Again, you
can solve many of the tape machine problems by "reading" the symptoms and making a logical
conclusion.
a. For still another example of a problem, let us assume that when you make an audio recording
and play it back, you don't get a signal. There are two ways to start checking. Use a known good
machine to check the tape or a known good tape to check the machine. If you determine that the trouble
is in the record or playback portion, you should proceed to check out the items in those sections.
b. If the trouble is in the record circuits, you may check the input source or the bias oscillator;
either one could cause a failure in the record mode.
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