SCP SCIENCE DigiPREP, Service Manual

Page: 25 / 88

KeyPad
Version 1.0
SCP SCIENCE
25
THE CONTROLLER IS NOT FUNCTIONING
WHEN THE POWER SWITCH IS ON
•
Ensure the power cord is fully inserted into its
socket (see Figure 2).
• Unscrew the bottom plate by removing the 4
screws holding the feet in place.
• Verify that the F1 Fuse is ok. (see fi gure 11 and 12
for part location.)
•Replace by a 0.75A if necessary
•Verify the 2 fuses along the KeyPad housing are
ok.
•Replace them by a 15A if necessary.
•Verify all the power cable connections.
•Green wire is connected with "Earth GND"
• Black wire of the fi lter is connected with the 15A
fuse holder; the black wire from the fuse holder,
with the power switch; the black wire of the
power switch, to "HOT" pin.
• White wire of the fi lter is connected with the 15A
use holder; the white wire from the fuse holder,
with the power switch; the white wire of the
power switch, to the "NEUTRAL" pin.
•Use a multimeter to measure the following
voltages (see fi gure 13):
•Place the negative lead of the multimeter on
TP1GND. Place the positive lead of the multimeter
on TP1. You should measure about 160 Vdc
for 120 Vac input supply or 300 Vdc for
240 Vac input supply. If the voltage is much
lower, measure the voltage across the cathode
and anode of diodes D3, D4, D5 and D6. You
should read about 63Vdc for 120 Vac and
125 Vdc for 240 Vac. If not, replace the
faulty diodes.
• Place the negative lead of the multimeter on
TP2, which is the ground test point. Place the
positive lead of the multimeter on TP3, which is
the +12V test point. You should measure
between 11.8 Vdc and 12.2 Vdc. If not, meausre
the voltage across U1-1 and U1-2, and U1-4
and U1-3, you should read respectively 1.2V
and 0.2 V. If not, replace U1.
• Measure the voltage across U3-1 and GND. You
should read about 2.5 Vdc. If not replace U3.
• Place the negative lead of the multimeter on TP2
and the positive lead on TP4, which is the +5.0V
test point. You should measure between 4.9 Vdc
and 5.2 Vdc. If not replace U4.
• Place the negative lead of the multimeter on TP6,
which is the analog ground test point. Place the
positive lead of the multimeter on TP5, which is
the AVCC test point. You should measure
between 4.9 Vdc and 5..2 Vdc. If not, replace
U5.
FIGURE 11: AC POWER CONNECTORS & FUSE F1 LOCATION
Legend
1. Fuse F1 (0.75A)
2. EARTH GND connector
3. NEUTRAL connector
4. HOT connector