Probable Cause
Trouble
Remedy
Winding on toroid may be open. Check
Transient response is poor
If winding is open, replace toroid, or
repair if feasible.
(cont.)
to see if there is a voltage drop across
R45 which would indicate such an
opening.
Monitor filament voltage with Triplett
A change of 0.1 volt or more in fila-
Meter on 12 volts while injecting a
ment volt age while a transient is being
transient. Adjust filament potenti-
injected will cause output to increase
excessively.
ometer R47 so that filament voltage is
6.3V dc on low side.
Amplifier peaks up on low
If reading is not 0, replace tube V2.
V2 defective. Check potential on grid
frequency end of frequency
of tube (pin 7) using voltohmist.
response
Voltage should read 0.
Remove short or replace scope con-
This may be due to a ground at scope
Gain is high
connector J7. This would short out
nector.
the negative feedback. The ground
may or may not be intermittent.
Check switch; replace if defective.
High hum in last stages
Defective microswitch. (CALI-
BRATE SIGNAL control. ) Hum
turns out to be calibrating signal.
Check capacitor; replace if defective.
Amplifier is noisy
Capacitor C1 on plate of first stage.
It may be noisy.
Replace R22.
Resistor R2 is noisy. Short one end
of R22 to ground; short other end. If
noise does not decrease, fault lies in
R22.
Filter capacitor C14 may have one
Replace capacitor if necessary, or
Filaments will not regulate
Voltage is low. Rectifiers
side shorted to the case. Measure
remove short.
get hot.
from one side of filament to ground.
Should not be dead short.
Replace defective diodes.
Diodes CR5, CR6, CR7, and CR8
Filaments will not regulate
have incorrect or faulty resistance.
or regulation is poor
Remove all diodes and measure
forward and reverse. Resistance
should be 2-3 ohms forward, and
over 500 ohms in reverse.
Figure 1-28. Troubleshooting Chart Vibration Meter Type 1-117-0105 (Sheet 3 of 3)
b. Adjust the SENSITIVITY control for the channel
and adjust the CALIBRATE SIGNAL control until a
under test to obtain a full-scale reading (CALIBRATE
full-scale reading is obtained. This corresponds to a
SIGNAL control released; channel selector set to the
theoretical transducer sensitivity of (15 x 10) = 150
channel under test; INPUT NETWORK selector switch
mv/in./sec = S. As an example, for 5 in./sec aver-
set to OUT).
age velocity:
c. Inject a sine wave signal into the CHANNEL con-
M VRMS = (1.11) (S) (Vaverage )
=
nector corresponding to the channel under test from
(1.11) (150) (5) = 833 mv
1-29
