Circuit Board Removal - Cooper VR-32 Installation, Operation And Maintenance Instructions

CHECK NO. 7 - RAISE AND LOWER RELAY CIRCUITS
If the symptoms of the malfunction indicate the problem may
be in the RAISE or LOWER relays, they may be checked as
follows:
1. Set the control for 120.0 V setting, 2 V bandwidth, and 10
second time delay.
2. Apply 120.0 V ac to the EXTERNAL SOURCE terminals,
place the power switch. on EXTERNAL, and the AUTO/
OFF/MANUAL switch on AUTO.
3. Connect the multimeter to TP 0 , set for dc volts of a scale
to read up to 28 volts. Connect the positive meter lead to
TP 9 , and expect to measure approximately 28 volts.
4. Now, slowly vary the applied voltage to below 119 V. After
the 10 second time delay period, the RAISE relay should
close and the voltage at TP 9 should drop to less than 1 V.
After 4 seconds, the relay will open and TP 9 will again
measure 28 volts.
5. If the relay does not close (pronounced "click" should be
heard), but TP 9 does go low, the problem is a defective
RAISE relay coil. If TP 9 does not go low, then the problem
may be a defective IC 7 .
6. Now, reconnect the multimeter to TP 9 and expect to mea-
sure approximately 28 V.
7. Bring the applied voltage back into band and hold it in
band for approximately 15 seconds. (This is to "clear" the
memory on the relay retry feature.) Now, vary the voltage
to above 121 V, and after the 10 second time delay period,
the LOWER relay should close and the voltage at TP 9
should drop to less than 1 V. After 4 seconds, the relay will
open and TP 9 will again measure 28 volts.
8. If the relay does not close (pronounced "click" should be
heard), but TP 9 does go low, the problem is a defective
LoWER relay coil. If TP 9 does not go low, then the prob-
lem may be a defective IC 7 .
9. Now, remove the multimeter from TP 0 and TP 9 , and set it
to read ac volts up to 125 volts. Connect the meter to the
terminal position labeled G (position 12) and LOWER
(position 3) on the output terminal strip of the circuit
board.
10. As the LOWER relay contacts close, approximately 120 V
should be measured. The contacts remain closed, howev-
er, for only 4 seconds, and then open for 30 seconds
before again closing.
11. If voltage is not measured when the contacts close, then
the LOWER relay is defective. Note: Be certain the
AUTO/OFF/ MANUAL switch is in the AUTO position.
12. Bring the applied voltage back into band and hold it in
band for approximately 15 seconds. Now vary the voltage
to just below 119V.
13. Connect the multimeter to the terminal position labeled G
(position 12) and RAISE (position 5) on the output termi-
nal strip of the circuit board.
14. As the RAISE relay contacts close, approximately 120
volts should be measured. The contacts remain closed,
however, for only 4 seconds, and then open for 30 sec-
onds before again closing.
15. If voltage is not measured when the contacts close, then
the RAISE relay is defective. Note: Be certain the
AUTO/OFF/ MANUAL switch is in the AUTO position.
CHECK NO. 8 - OPERATIONS COUNTER
If the symptoms of the malfunction indicate the problem may
be in the operations counter, it may be checked as follows:
1. Set the control for 120.0 V setting, 2 V bandwidth, and 10
second time delay.
2. Apply 120.0 V ac to the EXTERNAL SOURCE terminals,
place the power switch on EXTERNAL, and the AUTO/
OFF/MANUAL switch on AUTO.
3. Connect the muiltimeter to TP 0 , set for dc volts of a scale to
read up to 28 volts. Connect the positive meter lead to
TP 10 , and expect to measure approximately 28 volts.
4. Momentarily connect a 1000-ohm, 20-watt resistor from G
to HS on the fanning strip which leads to the back panel.
(This assumes the fanning strip is connected to the output-
terminal strip of the circuit board.)
5. The voltage measured at TP 10 should drop to less then 1
volt and the operations counter should partially increment as
the resistor connection is maintained. When the connection
is interrupted, TP 10 should go high and the operations
counter increment should complete.
6. If the counter does not increment, but TP 10 , does go low,
the problem is a defective operations counter. If TP 10 does
not go low, then the problem may be a defective IC 7 .
CHECK NO. 9 - WATCHDOG CIRCUIT
If the control appears completely dead and voltage measure-
ments external to the circuit board indicate that a voltage source
is being delivered to the board, a problem could be occurring in
the watchdog circuitry. This is checked by connecting an oscillo-
scope between TP 0 and TP 12 , while the circuit board is ener-
gized. A pulse train of approximately 5 V amplitude, occurring at
least every 150 milliseconds, should be observed. Now connect
the oscilloscope probe to TP 11 and a dc voltage of at least 3.0
volts should be measured. If the pulse train is not present, or
TP 11 is not above 3.0 volts, then either the microprocessor (ICI)
or watchdog (IC 5 ) are defective. Further analysis requires dis-
connecting or isolating the two components as the loading
effects from one device can affect the other device.
No attempt should be made to further analyze these problems
or to replace IC 1 . Contact Cooper Power Systems service for
board exchange.

CIRCUIT BOARD REMOVAL

The printed circuit board can be physically removed from the
control and yet remain electrically connected for test purposes.
To keep the printed circuit board electrically connected to the
control, follow the numbered steps, but DO NOT disconnect the
fanning terminal strip as described in Step No. 1.
1. Loosen the screws on the interconnecting terminal strip on
the printed circuit board to drop the fanning strip clear.
2. Remove the counter quick disconnects.
3. Loosen the locking strips on the bandwidth knob and the
time-delay knob and turn them until they clear the knobs.
4. Remove the time-delay knob.
5. Remove the bandwidth knob.
6. Remove the panel nuts from the bushings that are located
under the knobs.
7. Loosen the two side screws that are engaged in slots at the
bottom of the board frame to allow free movement of the
printed circuit board.
8. Swing the top of the board away from the front panel until
the control shafts are clear. Lift the board free of the slots in
the side brackets (Figure 4-4).
The replacement of the printed circuit board is accomplished
by following the above steps in the reverse order. To correctly
orient the knobs, observe the flattened shaft and corresponding
knob cavity.
By leaving the fanning strip attached to the printed circuit
board removed from the control, it is possible to thoroughly test
the entire control assembly. The fanning strip concept provides
reliable screw-down-type terminals for rapid removal and
replacement.
S225-10-5
4-10