Chevrolet DB90 Series, Service Manual

Page: 148 / 242

S ec. 6Y-142
A. C. GENERATING SYSTEM (NON-INTEGRAL TYPE)
OUTPUT BASE RESISTOR
(PART 13, F ig. 28)
If one reading is infinite or nearly infinite, or
if both readings are infinite or nearly infinite, the
r e s is to r is open.
DRIVER TRANSISTOR
(PART 14, 14A, 14B, F ig. 28)
If both readings in Step 14 are zero or if both
readings are very low and identical, the tra n sisto r
R E L A Y B A S E
C O IL C H E C K B A T T E R Y
1 -5 5 9 4
Figure 3 2 —Full Transistor Type Regulator
is shorted and m ust be replaced. S im ilarly, if both
readings in Step 14A or 14B are zero or very low
and identical, the tra n sisto r is shorted.
If both readings in Step 14 or 14B a r e infinite,
o r if both readings are very high and id en tical, the
tra n sisto r is open and m ust be replaced.
OUTPUT TRANSISTOR
(PART 15, F ig s. 29 and 30)
In figure 29, if both readings in Step 1 are
zero , or if both readings are very low and identical,
the tra n sisto r is shorted. S im ilarly, if both read ­
ings in Step 2 or Step 3 are zero or very low and
id en tical, the tra n sisto r is shorted.
In figure 30, if both readings in Step 1 are
infinite, o r if both readings a re very high and
id en tical, the tr a n sisto r is open. S im ilarly, if both
readings in Step 2 a re infinite or very high and
id entical, the tra n sisto r is open.
PANEL BOARD ASSEM BLY
Figure 31 —Field R elay Unit Check
Figure 3 3 —Regulator w ith Bottom Plate Rem oved
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT