Chevrolet DB90 Series, Service Manual

Page: 146 / 242

S ec. 6Y -140
A. C. GENERATING SYSTEM (NON-INTEGRAL TYPE)
OUTPUT TRANSISTOR
INSULATORS M
TRANSISTOR MOUNTING
SCREWS
T-5590
Figure
2 5
—Heat
S
ink a n d Circuit Board A ssem bly
NOTE: The air gap norm ally need not be ad­
justed. If the point opening and clo sin g voltages
a r e within lim its liste d in "Specifications" at end
of this sectio n , the relay w ill operate sa tisfa c to r ily
even though the air gap may not be exactly a cco rd ­
ing to sp ecifica tio n s.
4. If adjustm ent is n e c e ssa r y , bend the flat
contact support spring.
REGULATOR REPAIR
(MODEL 1116374 OR 1116378)
To check the regulator (fig. 23) for d efective
com ponents p roceed a s follow s:
1. R em ove four sc r e w s which attach cover to
b ase plate and rem ove the co v er.
2. R eferring to figure 24, rem ove lead s from
term in a ls 1, 2, and 3, then rem ove sc r e w s 4 and
5 which attach relay to b ase and rem ove relay.
3. R em ove sc r e w s (6 and 7, fig . 24), then lift
circu it board, heat sink and term in al assem b ly
from the regulator b a se.
4. Note the insulation between the output tran­
s is to r and heat sink, and the in su lators separating
the heat sink from the panel board (fig. 25).
5. R em ove screw s which attach tr a n sisto r to
panel board and sep arate the tr a n sisto r and heat
sink and in su lators from the panel board.
6. V isu ally inspect a ll copper tr a c e s on the
panel board for opens and for sh o rts or grounds
which could be caused by sold er runs.
NOTE: An ohm m eter having a 1^-volt c e ll,
which is the type usually found in s e r v ic e station s,
is recom m ended for checking tr a n sisto r s andparts
ZENER
DIODE
T R A N S IEN T No 2
SUPPRESSIO N
DIODE
No
T R A N S ISTO R
□ n n n
R 4 EM ITTER
BASE RESISTO R
O U TPU T BASE
R 5 RESISTO R
. R3 V O LTA G E DIVIDER
R ESISTO R
f
R 2 PO TEN TIO M ETER
No. 3 C A P A C ITO R
AD JU STIN G ARM
HEATIN G PO INT
No. 1 TH ER M ISTO R
R1 V O LTA G E DIVIDER
R ESISTO R
No 6
O U TPU T No 5 No 7 BACK BIAS DIODE
TR A N S ISTO R FIELD DISCHARGE
(M OUN TED ON REVERSE SIDE) DIODE
REGULATOR
Figure 2 6 —Com ponent Parts o f Panel Board A ssem bly
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT