*ARM power
off*

a. ARM POWER is not 
turned on.

b. System malfunc-
tion.

a. Turn on ARM POWER and 
reenter last command.

b. See Symptom in Table 5-10
(ARM POWER does not come
on).

*Bad pot*
Jt n

Indicates pot
"reading" not 
changed during
"calibrate"
motion.

a. Faulty wiring in 
arm signal 
interconnect.


b. Faulty encoder/
potentiometer.



c. Faulty PC
board(s).

a. Inspect cabling from arm
signal board to potentiom-
eter at indicated joint.  
Replace if faulty.

b. Ensure potentiometer cap
is not loose or removed.  
Replace faulty encoder/
potentiometer.

c. Check seating.  Replace 
boards in the following 
sequence.  Recheck problem
after each step:

(1) "C" interface board.
(2) "A" interface board.
(3) Arm signal board.

Replace faulty board.

*Brake release
enabled*
Indicates 
BRAKE RELEASE
SELECT &
ENABLE switch 
enabled or 
circuit is 
faulty.

a. Switch is in a 
joint position.


b. Faulty selector 
switch.


c. Faulty PC 
board(s).

a. Move switch back to NORMAL.



b. Replace faulty switch 
assembly.


c. Check seating.  Replace 
boards in the following 
sequence; recheck problem 
after each step:

(1) "C" interface board.
(2) "A" interface board.

Replace faulty board.

*Broken 
encoder wire*

One of five 
wires to an 
encoder are
broken or 
disconnected.

a. All LEDs on 
arm signal 
interface board
on control 
backplane are 
lit.


b. Single joint 
LED is lit.



c. Faulty encoder/
potentiometer.

d. Arm signal board
defective.

a. Check continuity of all 
signal interconnect cable
connections.  Check 5 VDC
regulator on arm intercon-
nect board at robot base 
(regulator converts 12 VDC
to 5 VDc for encoders).

b. Check continuity of wiring 
from arm signal board to 
indicated joint.

c. Replace faulty encoder/
potentiometer.

d. Replace faulty arm signal
board.

*Calibration 
will move out 
of range*
Jt n

Arm lacks 
sufficient
range for 
calibration.

Arm too close to
end of range.

Reposition arm using teach
pendant in JOINT mode, and
repeat CALIBRATE command.

*Checksum 
Error*
Transmission 
error between 
floppy disk 
and control-
ler.

a. Diskette in use
is defective.

b. Defective or 
loose floppy 
drive connector.


c. Board(s) not 
securely seated.

d. Defective
board(s).












e. Electrical 
noise affecting
serial data 
transmission.

a. Retry using known good
diskette.

b. Check connection of floppy
drive.  If connection good, 
check continuity of cable. 
Replace cable if necessary.

c. Check boards in card cage
for proper seating.

d. Check seating.  Replace 
boards in the following 
sequence; recheck problem 
after each step:

(1) Quad serial interface
(DLV11-J board at slot
J34).
(2) LSI-11/73 CPU board.
(3) "B" interface board.
(4) CMOS board.

Replace faulty board.

e. Check wiring, especially
grounds at controller and 
VDT.

*Clock 
overrun*

VAL runs out 
of time when 
trying to 
compute next 
set of posi-
tion commands.

a. Defective "B"
interface board.

b. Defective 
LSI-11/73 CPU
board.

c. LSI-11/73 CPU 
board affected 
by electrical 
noise.

a. Replace defective board.


b. Replace defective board.



c. Ensure all covers correctly
installed.

*CPU error*
Trap to
from kernel:
9log,
phy),


*CPU error*
Trap to 
from user:
(log, 
phy), 


Computer error 
due to bad
read from mem-
ory or noise 
on data bus.

a. Bad read from 
memory.





b. Electrical 
noise on lines.





c. Defective
board(s).

a. Restart VAL II by typing
"1100G".
CAUTION
Responding with a Y 
will wipe out memory.


b. Isolate all high power or
high frequency lines as far
from robot as practical.
In some rare instances such
lines may require addi-
tional shielding.

c. Check seating.  Replace 
boards in the following 
sequence; recheck problem 
after each step:

(1) LSI-11/73 CPU board.
(2) CMOS memory board.

Replace faulty board.

*Data check 
error* 

Trainsmission error detected while
transferring in-
formation to and 
from external 
device.

Attempt transfer again.
Check wiring for proper
grounds; add shielding.

*Device not
ready*

Requested file
storage not pre-
pared to communi-
cate with VAL II.

On Unimation floppy disk
drive, make sure drive is
plugged in, diskette is 
inserted correctly, and door
is closed.

*Envelope 
error*
Jt

The actual 
position of a 
joint is be-
yond the VAL 
commanded 
position en-
velope.

a. Minor joint de-
generacy occurs 
when Joint 5 is
near 0 degrees, 
therefore align-
ing axes of 
Joint 4 and 6. 
Error occurs as 
VAL attempts to 
reposition 
Joints 4 and 6 
simultaneously 
for tool orien-
tation.

b. Excessive 
payload or 
speed.



















c. Mechanical drag
or binding.
















d. Joint stalled.










e. Major joint drop 
due to lack of 
power after
brake released. 
















f. Major joint runaway.


























g. Minor joint 
runaway.

a. Reprogram arm; include off-
set in Joint 5.













b. Ensure that payload is 
within specified limits.  
Ensure that SPEED setting
is within limits for pay-
load.  Reduce payload weight
or redistribute payload
mass so that distance be-
tween affected joint and 
payload is reduced.  Refer
to Table 1-8 for maximum
payload specifications.
WARNING
Before proceeding to step
c, ensure that arm is 
properly supported prior 
to releasing joint brakes 
in FREE mode.  Failure to
mechanically support the
arm will result in arm 
collapsing.


c.CAUTION
When testing for motor
drag using BRAKE RELEASE,
dynamic braking circuit 
will create an electri-
cal "dragging" effect.
(Refer to paragraph 4-4-3.)

Place affected joint in
FREE mode; ensure that 
brake is not dragging and 
there is no binding of 
gears or bearings.  Refer to 
Chapter 4 for inspection 
procedures for indicated 
joint.  Replace servomotor.


d. Free joint of restraint.
WARNING
Before proceeding to step 
e, ensure that arm is 
properly supported prior
to releasing joint brakes
in FREE mode.  Failure to
mechanically support the 
arm will result in arm 
collapsing.

e. Inspect two green LEDs on 
power amplifier base driver 
board (refer paragraph
5-3-3-4). If only one LED 
is lit, fault is in motor 
wiring.  Check for contin-
uity in the following:

(1) High-power interconnect
assembly.  

(2) Arm harness (call 
RP Automation Field Service
for assistance).

If both LEDs are not lit, 
loss of motor voltage is 
indicated.  Replace power
amplifier assembly.

f. Check electrical connec-
tions of affected joint.
Check cables for contin-
uity, replace if faulty.
Replace components in the 
following sequence: recheck 
problem after each step:

(1) Encoder/potentiometer.
Exchange boards to 
isolate fault.
(2) Digital servo board.
Exchange boards to 
isolate fault.
(3) Servomotor.
(4) Low power interconnect
cable.
(5) Arm harness (call
RP Automation Field Service 
for assistance).
(6) Power amplifier.
(7) Arm cable board (call
RP Automation Field Service
for assistance).

Replace faulty component.

g. Check electrical connec-
tions of affected joint.
Check cables for contin-
uity; replace if faulty.  
Replace components in the 
following sequence; recheck
problem after each step:
(1) Encoder/potentiometer.
Exchange boards to 
isolate fault.
(2) Digitial servo board.
Exchange boards to 
isolate fault.
(3) Servomotor.
(4) Low power interconnect
cable.
(5) Arm harness (call
RP Automation Field Service
for assistance).
(6) Power amplifier.
(7) Arm cable board (call
RP Automation Field Service
for assistance).

Replace faulty component.

*ESTOP error*

ESTOP circuit 
activated or 
defective.

Circuit is open.

Check for continuity in 
circuit.  Inspect ESTOP 
switches on controller and 
teach pendant.  Ensure teach 
pendant is connected and CX 
port is jumpered.

[FATAL]

NOTE

When [FATAL] appears on screen, it indicates
that a sufficiently serious problem has 
developed to cause the operating system to 
shut down.  For possible symptom look up
message, alphabetically, following word
[FATAL].

*Function 
timeout*
Jt

Indicated 
joint took too
long to com-
plete last
motion.

a. Robot is blocked 
and cannot reach 
its destination.

b. Arm has run into 
a hardware stop.


c. Joint stalled, 
arm unable to 
move to program-
med location.



d. Faulty electric-
al interconnec-
tion.




e. Defective 
board(s).

a. Turn on ARM POWER and try
motion again.


b. Change program steps or 
locations as necessary to 
avoid hardware stops.

c. Inspect operating envelope 
for physical barriers.
Inspect drive train for 
mechanical problems.
Inspect servomotor brake
systems.

d. Check seating of ribbon 
cable interconnecting "A"
interface board and "B" 
interface board.
Replace ribbon cable if 
faulty.

e. Check seating.  Replace 
boards in the following 
sequence; recheck problem
after each step:

(1) Digital servo board.
Exchange boards to 
isolate fault.  
(2) "B" interface board.
(3) "A" interface board.

Replace faulty board.

*Hardware 
defect*


Fault occurred 
in a power 
amplifier, or
cabinet over-
temperature 
tripped.

a. Major joint 
power amplifier
fault.

b. Minor joint 
power amplifier 
fault.


c. Overtemperature
switch on "C"
interface board 
tripped at 60 C.

a. Turn off system.  Allow time
to cool; then reinitialize.


b. Determine faulty amplifier;
then inspect LEDs to find 
cause of fault.  Replace 
amplifier if faulty.

c. Check LED at "C" interface
board.  Turn off power; al-
low cabinet to cool.  Check 
for abnormal heat gen-
eration.

*Hardware not
in system*

Hardware is 
not installed 
in system, or 
hardware mal-
functioning.

Defective or 
missing hard-
ware.

Proceed as follows:

(1) Save necessary programs 
and data.
(2) Turn off system.
(3) Install or repair hard-
ware module.
(4) If necessary, modify
programs so as not to 
attempt access to this 
hardware.

*High
acceleration
envelope
error*

Acceleration 
commanded by 
VAL in excess 
of normal; an 
envelope error 
results if 
executed.

a. SPEED command 
too high.

b. VAL II fault.

a. Lower SPEED setting.


b. Reload VAL II; reinitialize
system.

*Joint on limit
stop*

Limit switch
circuit act-
ivated on 
Joint 1, 2 or 
3, and system 
shuts down.

a. Robot arm 
rotated past 
software stop,
triggering 
limit switch
braking system.

b. Faulty limit
switch.

c. Faulty 
electrical 
interconnection.

a. Determine affected joint.
Reposition joint using
brake release and re-
initialize system.



b. Inspect limit switch; re-
place if faulty.

c. Inspect interfaces.  Check 
cables for continuity; re-
place if faulty.

*Lost encoder
sync*
Jt 

Lost encoder 
synchroniza-
tion occurs
when there is 
an incorrect 
number of 
counts between
the encoder
index pulses
(one index per
motor revol-
ution) or 
index is lost.

a. Electrical 
noise causing
incorrect 
encoder counts.




b. Faulty electri-
cal interconnec-
tion or poor 
ground.


c. Faulty encoder/
potentiometer.



d. Faulty digital
servo board.


e. Faulty arm cable
assembly.

a. Check shielding or encoder
signal wires.  Shields
should only be connected to 
ground at arm signal board.
Check arm and controller
for solid ground connec-
tions.

b. Inspect interfaces.  Check
cables for continuity;
Replace if faulty.  If arm
harness is faulty, call 
RP Automation Field Service.

c. Exchange harness connec-
tions to isolate fault.  
Replace encoder/potentiom-
eter if faulty.

d. Check seating.  Exchange
boards to isolate fault.  
Replace faulty board.

e. Check cable connection;
replace defective assembly
(call RP Automation Field 
Service for assistance).

*Motor stalled*
Jt

If servomotor
is not moving, 
or moves too 
slowly, and 
joint process-
or has com-
manded full
output for 3.2
seconds, an 
error is gen-
erated and arm 
power is shut 
off.

Robot arm 
restrained from 
moving to pro-
grammed position.

Free arm restraint.

*No zero index*
Jt

System did not 
detect zero
index for 
Joint n during 
CALIBRATE com-
mand.

a. Defective digi-
tal servo board.


b. Faulty encoder/
potentiometer.

c. Faulty
electrical
interconnection.

a. Replace defective digital
servo board of affected 
joint.

b. Replace encoder/potentiom-
eter of affected joint.

c. Inspect interfaces.  Check
cables for continuity; re-
place if faulty.

*Open failure*

VAL II unable 
to open a 
communication 
channel as re-
quested.

a. Remote computer 
is not respond-
ing.

b. Hardware problem 
in communica-
tions line.

a. Check that remote computer
is working properly.


b. Check that communications
hardware is working prop-
erly.  Reenter command.

*Out of range*
Jt

System init-
ialization
attempted 
when arm out
 of range or
faulty pot-
entiometer
signals occur.

a. Arm outside of 
or adjacent to 
robot arm oper-
ating envelope.


b. Faulty encoder/
potentiometer.



c. Faulty electri-
cal interconnec-
tion in poten-
tiometer
signals.

d. Faulty PC 
board(s).

a. Reposition arm.





b. Exchange harness connec-
tions to isolate servo-
motor.  Replace encoder/
potentiometer if faulty.

c. Check cables for contin-
uity; replace if faulty.  
If arm harness is faulty, 
Call RP Automation Field Ser-
vice.

d. Check seating.  Replace
boards in the following 
sequence; recheck problem
after each step:

(1) "B" interface board.
(2) "A" interface board.
(3) Digital servo board
Exchange boards to 
isolate fault.
(4) LSI-11/73 board.

*Servo dead*
Jt

Joint control-
ler for indi-
cated joint
not responding
to VAL com-
mands.

a. Faulty digital
servo board.


b. Faulty elec-
trical connec-
tion.




c. Faulty PC
board(s).

a. Check seating.  Exchange 
boards to isolate fault.
Replace faulty board.

b. Check seating of ribbon
cable connecting "A" 
interface board and "B"
interface board.  Replace
ribbon cable if faulty.

c. Check seating.  Replace
boards in the following
sequence; recheck problem
after each step:

(1) Digital servo board.
(2) "B" interface board.
(3) "A" interface board.

*Servo RAM
error*
Jt 

Joint process-
or detects 
faulty memory
during system 
startup.

Faulty digital
servo board.

Check seating.  Exchange 
boards to isolate fault.
Replace faulty board.

*Stopped due to 
servoing
error*

Program exec-
ution stopped 
due to one or 
more servo
errors.

One or more servo
errors.

Troubleshoot first error
described.

*Storage area
format error*

Momentary 
hardware fail-
ure may cor-
rupt user data
in RAM.  User
programs and
locations 
currently in 
memory may no
longer be
valid.

Momentary hard-
ware failure.

Attempt to save as much
data as possible onto
floppy disk.  Issue ZERO 
command or restart VAL II;
respond with a "Y" to 
initialization query.

*System clock
dead*

"B" interface 
board not seated
properly or
defective.

Check "B" interface board.
Replace board.

*Terminal 
interrupts
dead*

System inter-
rupt lines 
cannot be ac-
cessed or VDT
interrupts are
faulty.

Empty backplane
slots between
LSI-11/73 CPU
and serial I/O 
modules.

a. Check board installation to
ensure proper board place-
ment in card cage.

*Unknown FPS
error*

Error reported 
in hardware
CPU module by 
floating-point
processor.

LSI-11/73 CPU
board defective.

Shut down system and reseat 
LSI-11/73 CPU in card cage.

If problem persists, replace
LSI-11/73 CPU board.

FAULT indica-
tor lit.

The FAULT LED
is located in 
the CONTROL
section of the 
controller 
display panel.

LED is marked
Figure 3-1.

a. Brake release 
switch faulty.













b. Run indicator 
fault on :"C" 
interface board.




























c. Joint 1,2, or 
3 limit switch 
activated.








d. Major joint
power amplifier
fault.

e. Minor joint
power amplifier
fault.

f. ESTOP contacts
open.

g. OVERTEMP on "C"
interface board 
activated.

h. VAL ESTOP 
activated.

i. Servo ESTOP 
activated.

a. Ensure switch is in NORMAL
position; replace faulty
switch assembly.  Check 
board seating.  Replace
boards in the following
sequence; recheck problem 
after each step:

(1) "C" interface board.

(2) High-power function
board.

Replace faulty board.

b. Reinitialize VAL system.
Check low-power supply 
voltages; lack of all 
voltage readings indicates
blown power supply fuse.
Loss of a single voltage
indicates blown fuse, de-
fective power supply, or
bad connection.  Check the
following cables for con-
tinuity; replace if faulty.

(1) P88-P17 "C" to "A"
interface connection.
(2) P89-P28 "C" to "B" 
interface connection.
(3) P79-P103 Backplane
interconnection.

Check seating of the fol-
lowing boards.  Replace in
the following sequence and
recheck after each step:

(1) LSI-11/73 CPU board.
(2) CMOS board.
(3) DLV-11J quad serial 
interface board.

Replace faulty board.

c. Inspect LED on "C" inter-
face board.  Determine
affected joint.  Reposition
joint using brake release
and reinitialize system.  
Inspect limit switch; re-
place if faulty.  Check 
interfaces and cables for
continuity; replace if 
faulty.

d. Inspect LEDs on major joint 
power amplifier (refer to 
Table 5-17).

e. Inspect LEDs on minor joint
power amplifier (refer to
Table 5-15).

f. Refer to Symptom, "ESTOP
indicator lit."

g. Refer to Table 5-13, Symp-
tom "OVERTEMP indicator
lit".

h. Reinitialize VAL system.


i. Check P79 to P103 cable for
continuity.  Replace digital 
servo boards in sequence
with known good board.

ESTOP LED
indicator lit.

ESTOP contacts
open.

Check for continuity in
circuit.  Inspect all ESTOP
switches on controller and
teach pendant.  Ensure teach
pendant is connected or port
is jumpered.

JOINT LIMIT
SW. indicator
lit.  

Activated when
a major joint
triggers its
limit switch.

a. Robot arm has
rotated past
software stop;
limit switch
braking system
triggered.

b. Faulty limit
switch.


c. Faulty electri-
cal interconnec-
tion or poor 
ground.


d. "C" interface
board faulty.

a. Determine affected joint
(check indicator scales).
Use BRAKE RELEASE selector
switch, reposition arm, and
reinitialize system.


b. Check limit switch for 
continuity; replace if
faulty.

c. Inspect interfaces.  Check
cables for continuity; 
replace if faulty.  If arm 
harness is faulty, call
RP Automation Field Service.

d. Check seating; replace 
faulty board.

OVER TEMP 
indicator lit.

Indicator 
lights when
controller 
temperature
exceeds 60 deg C
(140 deg F).

a. Overtemperature
switch on "C" 
interface board 
tripped at 60 deg. C.


b. "C" interface 
board faulty.

a. Check indicator at "C" in-
terface board.  Turn off
power; allow cabinet to
cool.  Check for abnormal
heat generation.

b. Check seating; replace
faulty board.

Joint 1 (D5),
Joint 2 (D11),
Joint 3 (D23),
Joint 4 (D17),
Joint 5 (D29),
or Joint 6 
(D35) ENCODER
FAULT indica-
tor lit.

Broken encoder
LED activates
when power to 
encoder is 
interrupted 
or lines to
encoder sig-
nals are open.

a. Broken encoder
wire(s).


b. 5 VDC line is 
faulty.





c. Loss of ground.



d. Faulty encoder/
potentiometer.

e. Arm signal board
defective.

a. Check continuity of all
signal interconnect cable
connections.

b. Check continuity of 5VDC
wiring to indicated joint.
Check 5 VDC regulator on
arm interconnect board at
robot base; replace if 
faulty.

c. Check continuity of wiring
from arm signal board to 
indicated joint.

d. Replace faulty encoder/
potentiometer.

e. Replace faulty arm signal
board.

OVERCURRENT 
indicator 
(D11) lit.

a. Electrical
system faulty.



b. Degeneracy
in robot arm 
(degeneracy is 
a mechanical 
fault occurring
when Joints 4 
and 6 line up
during opera-
tion).

c. Faulty power
amplifier board.

a. Check cables and servomotor
for short to ground.  Re-
place faulty cable or 
servomotor.

b. Revise program to avoid
degeneracy.








c. Replace faulty board.

Both UNDER
VOLTAGE (D11)
and OVERCUR-
RENT (D12) 
are lit.

Power supply 
problem in power card 
backplane.

Check board seating.  Check 
for presence of 60 VDC and 
low voltage at backplane and 
low voltage at P108.  Replace 
cable P107-P108 if faulty.
Replace backplane.

MOTOR CURRENT
POSITIVE indi-
cator (D3) or 
MOTOR CURRENT
NEGATIVE indi-
cator (D4) 
not lit.

a. Faulty electrical 
connection 
internal to 
amplifier.



b. Interconnect
wiring open.

a. Inspect wire connections
into terminal strip on
power amplifier assembly.
Inspect cable connetion
into base driver.  Inspect
connection to inductor for
indicated joint.

b. Check interconnect cable
for continuity; replace if 
faulty.

MOTOR CURRENT
POSITIVE indi-
cator (D3) and
MOTOR CURRENT
NEGATIVE indi-
cator (D4)
not lit.

In normal 
operation, 
both indica-
tors are lit.
If motor wire
is open, indi-
cator for op-
posite current
will not 
light.  If both
indicators are
not lit, motor
voltage is 
missing.

a. Arm power off.





b. Faulty
electrical
connection from
transformer.



c. Blown fuse.

a. Ensure that ARM POWER is
turned on.  Refer to Table 
5-10, "ARM POWER does not
come on."  


b. Check for presence of 85
volts from transformer.
Ensure transformer is 
properly tapped.  Replace
transformer if faulty.


c. Replace fuse; if fuse
blows a second time, re-
place major joint power
amplifier assembly.

SYSTEM OK
indicator (D5)
not lit.

a. Faulty 
electrical 
interconnection.


b. Faulty interface
board.


c. Motor control
board faulty.

a. Check wire connections at
terminal block.  Inspect
ribbon cable P84-P85.
Replace if faulty.

b. Replace Power Amplifier
Assembly.


c. Replace Power Amplifier
Assembly.

OVERCURRENT
indicator (D6)
is lit.

a. Motor control
board faulty.

b. Faulty mechan-
ical drive 
train.

a. Replace Power Amplifier
Assembly.

b. Inspect drive train for
binding (refer to paragraph
5-5-1).

OVERSPEED 
indicator (D7)
is lit.

Not used on PUMA
model 761 and 
762.

Call rp automation Field Service
if indicator is lit.

CONTROL VOLT-
AGE LOSS (D8)

a. Voltage regula-
tor faulty.


b Faulty latch.


c. Faulty 
electrical 
interconnection.






d. Base driver
board faulty.

a. Contact RP Automation Field
Service for assistance.


b. Replace Power Amplifier
Assembly.

c. Inspect wire connectors
into terminal strip on 
power amplifier assembly.
Inspect cable connections
into motor control. Check
transformer input and out-
put voltages.  Replace 
power amplifier assembly.

d. Replace Power Amplifier
Assembly.

OVERTEMPER-
AUTRE (D9)

a. Excessive heat.



b. Base driver
board faulty.


c. Cooling fins
defective.

a. Turn off controller; allow
to cool.


b. Replace Power Amplifier
Assembly.


c. Ensure that adequate 
space is allowed for air
flow around fins.

22 VDC PRESENT
(D10) indica-
tor not lit.

a. 22 VDC supply 
is faulty.




b. Base driver 
board faulty.

a. Check for presence of 
supply voltage at trans-
former.  If 22 VDC supply 
is faulty, contact
RP Automation Field Service.

b. Replace Power Amplifier
Assembly.

PS FAULT (D15) 
indicator lit.

a. Brake release 
fuse blown.

b. High power 
function board
faulty

a. Replace blown fuse.


b. Check board seating; re-
place faulty board.