Du Pont SORVALL RC-5 Service Manual page 93

Drive
System
CircuitSorvall®
CentrifugesTable
4-6.
Troubleshooting Chart,
Brake
CircuitPROBLEM:
No braking
action.SYSTEM
CONDITIONS:1.
System in RUN.2.
"SPEED"
control
set
for5000
rev/min.Electrically
confirm braking
actionby
checking for the following two
vol¬tages
immediately following
thetermination
of a run with
BRAKESwitch
ON and SPEED control
setfor
5000
rev/ m
in:1.
At least 1 V dc across
R201.2.
Approx.
25 V ac across
R202.Brake
lamp circuit open.
Performcontinuity
check.AYESWith
system
in HOLD and BRAKE
switch
ON,is
BRAKE
lamp
ON?Problem
solved.NOReplace
S109 (RC-5) or
S103(RC-5B).A
NORemove
K208 and check for 115 V
acbetween
terminal A of K208
socketand
chassis
ground.
Is
voltagepresent?YESRemove
power.
Check for zero
resistancebetween
wires
442 and 213
on
PC-20126(RC-5)
or PC-50195
(RC-5B). Zero
ohms?NOReplace
fuse.
Blown
again?YESNOYESCheck
F301
(RC-5) and F301
and F303
(RC-5B).Are
fuses
blown?Remove
power. Replace F301.
Checkfor
short between
CR201
positiveterminal
and chassis
gnd.
Ifshorted,
trace
DC braking
loop.K208
defective
or 115 V
acabsent
at terminal
A of
K208socket.
Check K208 coil
forcontinuity.
Check for presenceof
115 V ac at terminal
A.If
coil open, replace
K208.If
115 V ac absent
trace
relaycircuit.NORestore
power.
Check for 10V
ac at
ACterminals
of CR201 with
F301
removed
(RC-5)or
K208
deenergized
(RC-5B).
Isvoltage
present?YESNOCheck
for at least 5 V dc
betweenCR201
positive terminal and
T201RED/YEL.
Replace F301. Is
voltagepresent?YESRemove
wire no. 492 on
PC-20126(RC-5)
or PC-50195 (RC-5B).
Checkfor
at least 1 V dc
acrossR201.
Is voltage
present?NOYESNORemove
power.
Check for open
circuitfrom
T201 RED/RED.
Remove lugs
fromCR201
AC terminals and check continuity.If
open, trace
17 V ac circuit
back
to17
V
winding.Remove
power.
Check for continuityin
DC brake loop. Remove wire
492on
PC-20126
(RC-5)
or PC-50195
(RC-5B).
Restore power.
Check for
atleast
1 V dc across R201
on
PC-20126(RC-5)
or PC-50195
(RC-5B).DC
excitation loop is
open.Remove
K202
and check contacts8
and 9 for proper
closure.Remove
power.
Check AC excitationloop
for continuity. Remove
wires492
and W600
YEL/WHT
on
PC-20126
(RC-5) or
PC-50195(RC-5B).
Check
betweenthese
wires for approx.10
ohms.
If open,
checkR202
for resistance.
Ifnormal,
check K202.
RemoveK202
and check contacts
4 and5
for proper
closure.a/79RCS/1454-12