TM 11-5826-225-35
Probable trouble
Procedure
Indication
Item
Check continuity of reference winding of B5.
Using transistor tester, check transistor Q22
110-CPS oscillator stage de-
fective.
With oscilloscope, check waveforms on base
and collector of Q22 (fig. 218).
Make voltage measurements (fig. 2-17).
Check continuity of coil L32 (para 2-9a).
Check transistors Q24 and Q25 (fig. 2-6).
Push-pull resolver servo am-
plifier stage.
Make voltage measurements on Q24 and Q25
(fig. 2-17).
Adjust R10 (para 3-19).
Balanced modulator balance
adjustment variable resis-
tor R1O.
Check continuity through switch contacts of
Loss of 110 cps on balanced
S14 (fig. 28). Clean contacts if corroded.
m o d u l a t o r by reason of
s w i t c h wafer S1D not
making contact.
Check transistors Q1 and Q3 (fig. 2-8).
First or second RF ampli-
fier stage defective.
Make voltage measurements (fig. 2-17).
Adjust R131 (fig. 2-8 and para 3-20).
Power supply variable re-
16
Erratic operation of bear.
sistor R131 out of adjust-
ing indicator.
ment (provides base and
I
emitter bias voltages for
first resolver servo ampli-
fier Q17).
See item 15.
110-cps oscillator or 110-CPS
amplifier defective.
See item 15.
Push-pull resolver servo am-
plifier stage.
Check transistors Q17 and Q18 (fig. 2-8).
First or second resolver
servo amplifier stage de-
fective.
Make voltage measurements (fig. 2-17).
Check transistors Q19 and Q20 (fig. 2-3).
Synchronous filter stage de-
fective.
Make voltage measurements (fig. 2-17).
Using oscilloscope, check 110-CPS waveforms
on bases of Q19 and Q20. Compare with
waveforms in figure 218.
Check transistor Q16 (fig. 2-3).
First agc amplifier defective
(emitter follower function
drives synchronous filter).
Make voltage measurements (fig. 2-17).
Using oscilloscope, check for presence of 110-
cps on base and emitter of Q16.
Note. Before continuing with items 17 and 18, set
control unit function switch to LOOP. Modulate signal
modulation. Using LOOP switch,
rotate bearing indi-
cator to aural null in headset.
Check filter capacitors.
Will not reach aural null Voltage regulator filter ca-
17
(sound will not cut off).
pacitor defective.
oscilloscope or ac range of vtvm, check
Using
Voltage regulator zener di-
for ac ripple on collector of
ode CR4 or CR1l, oscillat-
ing.
Q 3 0 and base of Q31 (fig. 2-6).
2-21
Change 1
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