Section 4
OM6636-B-00
12 February 2015
4-3
NOTE 2: If this reading is not obtained, check Q1.
Check the operation of the temperature sensitive oscillator. If the resistance of RT1/RT2
is greater than the resistance of Rl, then the oscillator should be running. Check with an
oscilloscope between TP1 (collector of Q102) and Pl-7. The waveform should be as
shown. If not, then check the following components:
Q101, Q102, C104, T101, C102, R103, R125, R104, R110
TP1
If oscillation is observed, then check between TP2 (collector Q103) and Pl-7. The
waveform should be as shown. If not, then check the following components:
Q103, C106, R117, R112, R106
TP2
If this waveform is observed, then measure the DC voltage between TP3 (CR104 anode)
and Pl-7. It should read -2.5 V. If not, then check C105, C107, CR103 and CR104. If
it is correct, then check Q104, Q105, R121, R122 and R114.
* Indicated waveform typical, if RT1 is at ambient temperature of about 25 C°.
As a further guide to trouble shooting, typical DC voltage at the transistor terminals are
given in Table 4-2.
