Chevrolet DB90 Series, Service Manual

Page: 147 / 242

S ec. 6Y-141
A. C. GENERATING SYSTEM (NON-INTEGRAL TYPE)
Figure 2 7 —Checking
Regulator Circuits
o f the panel board. The low range s c a le on the
ohm m eter should be used.
If a component part on the panel board is found
to be faulty, it should be replaced b efore p ro ceed ­
ing with the rem aining ch eck s. A 25-watt sold erin g
gun is recom m ended, and a 60% tin 40% lead sold er
should be u sed when r e -so ld e r in g . Avoid e x c e s s iv e
heat which may damage panel board tr a c e s. Com­
ponent parts a re identified in figu res 25 and 26.
In a ll of the follow ing ch eck s, connect the ohm­
m eter as shown, then r e v e r se ohm m eter lea d s to
obtain a second reading:
NOTE: R efer to fig u res 25 and 26 for id en ti­
fication and location of following connections:
7. To check component parts of the panel
board, it is n e c e ssa r y to carefully unsolder the
sp e c ific connections at points shown in figure 27.
FILTER CAPACITOR
(PART 8, F ig. 27)
If both ohm m eter readings are zero, the cap­
acito r is d efectiv e. V isu ally inspect for open so ld ­
ered connections and broken lea d s. To a ssem b le a
new capacitor p rop erly, note location of the "+”
identifying mark in figu re 26.
TRANSIENT SUPPRESSION DIODE
(PART 9, F ig . 27)
If the two ohm m eter readings a re iden tical,
the diode is faulty.
BACK BIAS DIODE
(PART 10, F ig. 27)
R ep lace the diode if both readings a re z ero , if
both readings a re infinite, or if both readings are
id entical.
Figure 2 8 —Checking Regulator Circuits
FIELD DISCHARGE DIODE
(PART 11, F ig. 27)
R eplace the diode if both readings are zero ,
if both readings are infinite, or if both readings
a r e identical.
EMITTER BASE RESISTOR (IF USED)
(PART 12, F ig. 27)
Connect ohm m eter as shown. If the reading is
infinite, the r e s is to r is open and must be replaced.
Figure 2 9 —Checking Transistors for Shorts
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT