Mitsubishi Electric CITY MULTI PUHY-400YMF-B, Service Handbook, Page: 140 / 204

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Power transistor
Measure resistances between each terminal of transistor module with tester, and use the results for troubleshooting.
Specified resistance value is dependent on tester type to be used for resistance measurement, because diode transis-
tor has non-linearity, thus difference of impedance and voltage in tester being influential. As the internal impedance of
resistance range of analog tester equals to the center value of meter indication, the affect of internal impedance can be
minimized if the tester having close center value of resistance range. Because internal voltage is normally 1.5 V, the
tester to be used for troubleshooting of transistor module should satisfy the following conditions.
The measured values for troubleshooting are shown in the table below.
(Use the minimum range for tester resistance range.)
Diode stack
Perform continuity check with tester. Judged as normal if the following characteristics are observed.
(Use the minimum range for tester resistance range.)
Internal voltage 1.5 V (Power source: one dry cell battery)
Central value of resistance range 10 ~ 40
Ω
C1
B1
E1 C2,E1
E2
B2
E2
C
B
E
Transistor module has 6
circuits shown in the left.
(See figure below.)
Tester
,
Tester .
C B E
C
∞ ∞
B 2 ~ 100
Ω
100 ~ 1500
Ω
E 2 ~ 100
Ω
100 ~ 1500
Ω
+ –
1 10 ~ 50
Ω ∞
2 10 ~ 50
Ω ∞
3 10 ~ 50
Ω ∞
+ –
1
∞
10 ~ 50
Ω
2
∞
10 ~ 50
Ω
3
∞
10 ~ 50
Ω
Tester
,
Tester .
Tester
.
Tester ,
1
2
3
+
–
1 2 3