User's Manual

PMAC User Manual
Troubleshooting 39
TROUBLESHOOTING
PMAC Card Troubleshooting
General
Is the green LED (power indicator) on PMAC CPU board ON, as it should be? If it is not, find out why
PMAC is not getting a +5V voltage supply.
Is the red LED (watchdog timer indicator) on PMAC CPU board OFF, as it should be? If it is ON, make
sure PMAC is getting close to 5V supply (at less than 4.75V), the watchdog timer will trip, shutting down
the card. The voltage can be probed at pins 1 and 3 of the J8 connector (A1 and A2 on the PMAC VME).
If the voltage is satisfactory, inspect PMAC to see that all inter-board connections and all socketed ICs
are well seated. If the card will not run with the red LED off, contact the factory.
Bus Communications
Do the bus address jumpers (E91-E92, E66-E71) set an address that matches the bus address that the
Executive program is trying to communicate with?
Is there something else on the bus at the same address? Try changing the bus address to see if
communications can be established at a new address. Address 768 (300 hex) is usually open.
Serial Communications
Is the proper port being used on the PC? If the Executive program is addressing the COM1 port, make
sure that it is cabled out of the COM1 connector.
Does the baud rate specified in the Executive program match the baud rate setting of the E44-E47
jumpers on PMAC?
With a breakout box or oscilloscope, make sure there is action on the transmit lines from the PC as you
type into the Executive program. If there is not, there is a problem on the PC end.
Probe the return communication line while giving PMAC a command that requires a response (e.g.
<CONTROL-F>). If there is no action, change jumpers E9-E16 on PMAC to exchange the send and
receive lines. If there is action, but the host program does not receive characters, RS-232 may be
receiving circuitry that does not respond at all to PMAC RS-422 levels. If using another model of PC, try
using it as a test (most models accept RS-422 levels quite well). If the computer will not accept the
signals, a level-conversion device, such as Delta Tau's Accessory-26, may be needed.
Commutation Troubleshooting
If there was no movement, check to make sure that output voltages were received on DAC1 and DAC2.
A value of 2000 should put 0.6V on the DAC lines. If voltage outputs were received from PMAC, but no
movement, check the amplifier and motor setups. If voltage outputs were not received, check the analog
supply to PMAC; make sure that the limits are held low or disabled; and make sure that the amplifier fault
signal is not indicating to PMAC that it has faulted.
Servo Loop and Jogging Troubleshooting
If holding position well, but cannot move the motor, make sure that the hardware limits are held low.
Check which limits I125 is addressed to (usually +/-LIM1), then make sure those points are held low (to
AGND), and sourcing current (unscrew the wire from the terminal block and put the ammeter in series
with this circuit to confirm this). If this is not right, refer to the Connecting PMAC to the System section
previously, and the PMAC Opto-Isolation drawing to re-check the connections.