Chevrolet DB90 Series, Руководство по обслуживанию

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S ec. 6Y-145
A. C. GENERATING SYSTEM (NON-INTEGRAL TYPE)
CHECKING
ZENER
DIODE
D
CHECKING
BACK-8IAS
DlODfc
CHECKING
FIELD-
DISCHARGE
DIODE
F
UNSOLDER
CHECKING
SUPPRESSION
DIODE
CHECKING CHECKING
FILTER FEED-BACK
CAPACITOR CAPACITOR
T -7 6 5
CH ECKIN G CH ECKIN G
CHECKIN G V O LTA G E- V O LTA G E-
DRI VER-COLLECTOR DIVIDER DIVIDER
RESISTOR RESISTOR R 3 RESISTOR R-5
A B C
CHECKIN G
POTENTIOMETER
CH ECKIN G
POTENTIOM ETER T766
Figure 3 6 —Checking Regulator Circuits
ZENER DIODE (D2),
(PART D, F ig. 36)
R eplace the diode if both readings are zero,
o r if both readings a r e infinite.
BACK-BIAS DIODE (D l),
(PART E, F ig. 36)
R eplace the diode if both readings are zero,
if both readings are infinite or identical.
FIELD-DISCHARGE DIODE (D3),
(PART F, F ig. 36)
R eplace the diode if both readings are z ero , if
both readings are infinite, or if both are identical.
DRIVER-COLLECTOR RESISTOR
(PART A, F ig. 37)
If both readings are infinite, the r e s is to r is
open.
VOLTAGE-DIVIDER RESISTOR (R3),
(PART B, F ig. 37)
If one reading is infinite or nearly infinite, or
if both readings a re infinite or nearly infinite, the
r e s is t o r is open.
VOLTAGE DIVIDER RESISTOR (R5),
(PART C, F ig. 37)
If one reading is infinite or nearly infinite, or
if both readings a re infinite or nearly infinite, the
r e s is to r is open.
Figure 3 7 —Checking■ Regulator Circuits
POTENTIOMETER
(PARTS D AND E, F ig. 37)
If one reading is infinite or nearly infinite in
P art D, the potentiom eter is open. If both readings
a re infinite in P art E, the potentiom eter is open.
NOTE: When installing a new potentiom eter,
mount on panel board and turn the potentiom eter
adjustm ent to the m iddle position . Then, after a ll
t e s ts have been com pleted and the unit has been
a ssem b led as shown in figure 34, connect the regu­
lator to a generator and adjust the potentiom eter
to 14 v o lts. With the adjustm ent le v e r in a v ertica l
p osition (fig. 34) u se a sold erin g iron to m elt the
adjusting le v e r into the potentiom eter.
EMITTER-BASE RESISTOR
(OHMMETER CHECK NOT ILLUSTRATED)
Since the r e s is to r has been unsoldered from
the panel board at one end, m erely connect an ohm ­
m eter a c r o s s the r e s is to r - an infinite reading in ­
d icates an open. R eplace if defective.
DRIVER AND POWER TRANSISTORS
(R efer to Fig. 29)
If both readings in Step 1 are z ero , or if both
readings are very low and id entical, the tr a n sisto r
is shorted. S im ilarly, if both readings in Step 2,
o r in Step 3, a r e zero or very low and identical,
the tr a n sisto r is shorted.
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT