5.4.1
I
2
3
4
5
1.
2.
3.
Current Mode Section, Limit Settings
Set unit POWER switch to OFF. Short output terminals and set CUR
RENT control to 100% and VOLTAGE control to 50%.
Set potentiometer R54 on the PCB to about 20% rotation. Set POWER
switch to ON and adjust R54 to the limit stated in specifications Table
5-3,
upper limit set point.
To preset for zero output current, adjust the CURRENT controls fully
counterclockwise. Adjust R53 until the current meter is just above
zero and will indicate upscale as soon as the FINE CURRENT control is
adjusted clockwise.
4.
Turn unit POWER switch to OFF.
Remove short. (Test complete).
Table 5-1 DCR-B Troubleshooting
No output (voltage mode)
Fuse opens or circuit
breaker trips
High output voltage
(meter pointer pegs)
No output (current mode),
or unit will not current
limit
Output oscillates (current
mode)
a)
Wrong input voltage
b)
Open fuses and circuit breakers*
c)
Reference voltages (check levels)
d)
Defective IC2 or IC3
e)
Collector to emitter short on Q3,
QS, Q6, Q7 or Q8
f)
Q2 open or shorted
a)
CR7 shorted*
b)
Input capacitors shorted*
c)
CR8, CR9, CRlO, CRll shorted or open*
a)
Sensing or programming leads or link
open*
b)
Defective IC2 or IC3
c)
Q4 shorted collector to emitter
d)
QS open collector to emitter
e)
CR7 shorted*
a)
Defective ICS
b)
Cl4 shorted
c)
CR13 open
d)
Shorted COARSE CURRENT potentiometer*
e)
Collector to emitter short on Q3,
QS, Q6, Q7 or Q8
f)
Q2 open or shorted
a)
Potentiometer R45 on unit PCB im
properly adjusted
*Chassis components (ref. Figure 6-4)
Maintenance
5-2
Rev B (6/84)
