Service manual

STP 11-25R13-SM-TG
F - 4
c. Monostable MV.
(1) Without an input trigger pulse, the monostable MV remains in its static condition. When the
circuit is not developing an output, it must be determined if the multivibrator is at fault or if the trigger
circuit is at fault. There must not only be an input trigger; it must also have sufficient amplitude to trigger
the circuit. If a stable trigger is present and there is no output, then the trouble is localized to the MV
circuit.
(2) Refer to Figure F-3. An open in any part of the circuit would in most cases eliminate the pulses
in the output. A short could have the same effect if it occurred in either transistor, but the results may be
slightly different for different parts of the circuit. If R23 were to short, the output pulse width would no
longer be adjustable. If a short or open is suspected as being the probable cause of a malfunction, an in-
circuit voltage or resistance check compared with known good readings would be useful in identifying the
faulty component.
Figure F-3. Monostable Multivibrator