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Servi ce
S
ERV
IC
E
S
HEE
T 4 (Cont'd)
Wh e n
t
he line
v
ol tage
i
s
r
em o ve d, C R 7
i
s
f
orw ard .-
bi ase d by
t
he curren t flo win g to the
P
ower M eter
begins to turn
o
ff. Th e co llector voltage b egins to
cir c uits fr om
t
he b attery. C R 6
i
s t urn e d
o
ff and no
go positive and
t
he ch ange
i
s tr ans mitte d
t
hrough
curr e n t flow s t hro ugh
t
he c harging cir cuit .
R
51 and VR5 to Q18 .
A
s Q18 begins to turn off,
i
ts
coll ector goes more n egativ e . Α negat iv e going
Current Lί m ίter
.
t r ansient
i
s coupled
t
hrough R55 to th e b ase of Q14
whi ch speeds up the turn -o ff
t
ime. Th e positive
If
t
he curr e n t flo w
t
hrou gh
t
h e 24V reg ulato r w e r e
supply voltage
i
s
r
emov e d from
t
he collector of
to sudd e nly in c r ease to appro ximate ly 90 mA, Q15
Q18 and also the
D
C Amplifi er.
A
s th e battery
would
t
urn on and dr aw the driv e current a wa y
voltage
i
s further redu ced, th e series r egul ated
from Q16 . Co nsequently , the cur rent flow to Q13
output begins to decr ease
f
aster
t
han
t
h e battery
would di sappear and
t
he r egul ato r
o
utput w o uld
voltage and, eventually, t h e 3
v
olt thresh old volt-
be re du ced .
age
i
s exceeded. Q14
i
s th en biased on, bu t,
because the battery vol tage
i
s less than 20 Vdc,th e
T
R
O
UBLE
S
H
OOTI
N
G
kn ee
v
oltage ofVR5 cannot be
r
each ed. Ther efore,
VR5 does not condu ct and Q18
r
em a in s biased off.
Set t h e LINE swi tc h to OFF and r e m ov e Α 4Ρ 1(red
wir e) fr om A 4J 1 and Α4 Ρ 2 (blue wire) fr o m A4J 2.
Thi s disconn ects the
l
oad fro m
t
he p ow er supply .
If
t
he s upply vo ltages a r e now correct, t he m al-
If α battery has been placed in
t
h e
P
ower Meter as
fun cti on is not in
t
he power supply .
α second a ry p ower so urce,
i
t
i
s al way s bein g
charged wh enever
t
he line
v
oltage
i
s coupled to
If, after r e m oving th e
l
oad, the output
v
ol tages
the in strum ent and
t
h e LINE swi tc h i s ON. With
measured are
l
ess th an norm al but of equ al and
ac lin e (Mains) power supplying e n ergy VR 3
i
s
oppos ite pol arity, th e m alfun cti on is pro ba bly in
t
urn ed on, which biases Q12
f
or α ch arging cur-
the seri es
r
egul ator cir cuits .
rent ofapproxim ate ly 90 mA. This curr e n t
i
s supp-
lied through
C
R6 to th e battery ΒΤ 1 . C R7
i
s
V
ol tages s hown in pa ren t h es is ar e
f
or battery
reverse biased while t he battery is be ing char ged.
o per ati on only .
B attery C
h
arger
M
ode l 435Β
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