Farnell TOPS 3D - Recalibration

10
Repair and recalibration should only be attempted by personnel
fully conversant with the hazards of working on ac mains powered
equipment.
At all times the safety earth must be connected and the protective
covers over the mains switch on the front panel and over the
transformer input tags and input fuse must be in place. The ac
mains power should only be applied when essential for testing
and calibration.
RECALIBRATION
If necessary the unit can be returned to Farnell Instruments
Limited
or
their
agents for
repair
and
recalibration.
Equipment needed.
Voltage reference source to within 0.05% capable of supplying
1mV, 395mV and 39.5V.
4/2 digit DMM to read voltage/ current within 0.01%
Suitable resistive loads and test leads.
CONTROL SECTION
Whilst it is possible to adjust the potentiometers mounted on the
control board it may be found easier to remove the display by
releasing 2 x M3 screws each side.
1
Check that fuse values fitted are as indicated on back panel,
Connect to a suitable supply and switch unit on.
Turn the bipolar output 'voltage adjust' control fully anti
clockwise, adjust P3 (set min V) to give an output voltage
at the -ve output terminals of 4.90 volts.
2. Turn 'volts adjust' fully clockwise and adjust P2 (set max V)
to give an output of 17.1 volts.
3. Turn P1 (set max l) fully clockwise, and connect load in series
with reference ammeter to -ve output terminals and adjust
load to give 1 amp at 17 volt output.
4. Turn P1 anticlockwise until 'overload' led in -ve output switch
just illuminates. Back off P1 slightly until led extinguished.
Remove load and ammeter.
5. With 'volts adjust' still fully clockwise, connect reference
voltmeter across the positive output terminals and adjust P5
(set balance) to give a reading of 17.1 volts (i.e. within 2
digits of -17 volt reading).
6. Rotate P6 (set max l) fully clockwise and connect load in series
with reference ammeter to + ve output terminals and adjust
until load current is 1 amp.