Cooper VR-32 Installation, Operation And Maintenance Instructions page 37

B. Switch the LDC control to (+X+R) and operate the
coarse REACTANCE control through all positions.
The voltage reading in each switch position should be half
the dial setting. This reading cannot be taken as precise,
unless a current source, virtually free of high-order har-
monics, is used. This is not normally available in a typical
test set up. The unit is calibrated at the factory and any
trouble should be indicated by a significant deviation from
the values provided in this trouble shooting outline. In this
case, a deviation indicates a detective REACTANCE
switch (X1 ) or reactor (X3).
10. Set the coarse REACTANCE control at 10 volts. Rotate the
fine REACTANCE control through all positions. The volt-
age reading at each position should be half the sum of 10
plus the respective fine REACTANCE control setting. A
deviation indicates a defective fine REACTANCE switch
(X2) or reactor (X3).
11. Set the coarse REACTANCE control at 10 volts and the
fine REACTANCE control at zero (0), and then switch the
LDC CONTROL through (-X+R) and (+X-R). The reading
should remain constant. A deviation indicates a defective
LDC CONTROL switch.
If the results of all the previous linedrop compensation tests
deviate significantly from the values provided in this outline, the
LDC CONTROL switch or the auxiliary current transformer
(ACT) are the most likely problem areas.
If all the above checks are satisfactory, the trouble is likely to
be in the printed circuit board. Refer to the Circuit Board
Trouble Shooting procedures which follow.
CIRCUIT BOARD TROUBLE SHOOTING
Recalibration
This precise check should be made on a service bench with the
control removed from the control box. (See instructions for con-
trol removal and replacement on page 1-7.)
CAUTION: Use only a high impedance (3000
ohms minimum) RMS meter for measurements.
VOLTAGE LEVEL SETTING AND BANDWIDTH
1. Switch the POWER switch to EXTERNAL.
2. Switch the LlNE-DROP COMPENSATION control switch to
OFF.
3. Set the VOLTAGE SETTING control to 120 volts.
4. Set the BANDWIDTH control to 2 volts.
5. Connect an accurate, true-RMS-responding voltmeter of at
least 3000 ohms impedance to the VOLTMETER terminals.
6. Connect a variable external 50/60-Hz voltage source with
less than 5% harmonic content to the EXTERNAL SOURCE
terminals.
7. Close dipswitch position 3.
8. Raise the applied voltage approximately 120 volts and adjust
until the band indicators stop flashing, indicating mid-band.
9. The voltage applied should be 120 ±0.25 volts act If not, set
the applied voltage to exactly 120.0 volts ac and adjust R10
(voltage level calibrator) on the printed circuit board until
both indicators are off.
10. Slowly vary the input voltage up and down, noting the points
that the HIGH and LOW visual indicators switch on. These
points should be symmetrical, and should be one volt above
and one volt below the 12O-volt nominal setting with an
accuracy of .3 volt.
If this is not true, proceed with the trouble shooting section.
WARNING: Care must be exercised if the printed
circuit board is to be removed or tested while the
control is energized. Shock hazard is present.
It is convenient to troubleshooting printed circuit board circuitry
while it is mounted in the control; however, the board can also be
checked after it is removed from the control. The board should
be serviced in a properly equipped service facility and not in the
field. In this section use Figure 4-3 to assist in trouble shooting.
The use of in-circuit component testers should be avoided
since their use can cause damage to the microcomputer IC1. All
soldering and unsoldering must be done with an isolated solder-
ing iron. Good anti-static procedures must be followed during
component replacement.
Replacement of the microcomputer is to be avoided. Return
the printed circuit board to an approved service facility for repair.
PRINTED CIRCUIT BOARD LEFT IN THE CONTROL
1. Set the LlNE-DROP COMPENSATION control to OFF.
2. Set the POWER switch to EXTERNAL.
3. Set the VOLTAGE SETTING to 120 volts.
4. Set the BANDWIDTH to 2 volts.
5. Set the TIME-DELAY to 20 seconds.
6. Apply a 50/60-Hz, 120-volt ac nominal variable source to the
EXTERNAL SOURCE terminals, making sure that the
source ground is connected to the panel ground (white
post).
PRINTED CIRCUIT BOARD REMOVED FROM THE CONTROL
1. Set the BANDWIDTH control two positions clockwise from its
extreme counterclockwise position.
2. Set the TlME-DELAY control two positions clockwise from its
extreme counterclockwise positions.
3. Connect a 120-volt ac supply to V3 terminal (13) and G
(ground) terminal (12). observe ground.
4. Connect one end of a 390-ohm ±2% resistor to either INPUT
terminal (10 or 11) on the printed circuit board.
5. Connect the other end of the 390-ohm resistor and the other
printed circuit board INPUT terminal to a variable isolated
60-volt ac, 50/60 Hz supply.
The input voltage and equivalent bandwidth on the printed circuit
board are related to 600-volt ac and are, therefore, one-half the
120-volt ac level applied to the control.
Note on the lower left-hand side of the circuit board a 16 pin
connector. Each pin of this connector corresponds to a test point
as shown on the schematic diagram in figure 4-3. The pin desig-
nations are TP , TP , TP , --- TP
O 1
2
Also, immediately above the connector is a swaged terminal
which is connected to TP
O
attachment when making circuit board measurements.
CHECK No. 1 - POWER SUPPLY AND REFERENCE
The following measurements can be made with a multimeter with
an accuracy of 2%, having at least 5000 ohms/volt dc and
1000ohms/volt act The inputvoltage will either be held in band or
varied from band edge to band edge.
S225-10-5
, labeled from top to bottom.
15
. This provides an alternate point of
4-4