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SECTION 7
SERVICE INSTRUCTIONS
2.
Refer to Service Instruction B to open
front cover.
3.
Disconnect
the
termina!
connectors
at
end of wire harness (12 Fig. 12) from the
MC board by pulling them straight out.
4.
Remove the 1/16" (1.6 mm) hose attached
to the transducer (14 Fig. 12).
5.
Remove the four screws (6 Fig. 12) that
secure
the
board
to the
cabinet
and
remove the MC board.
6.
Install the
new
MC
board
and
secure
it
using the four screws.
7.
Reconnect
the terminal
connectors
and
transducer hose.
8.
Close front cover and secure with cabinet
fasteners.
. Normal! Cycling Sequence of DeVO/MC44
When
pressure test gauges are attached to
the test points (Fig. 22) on the manifold the
following
cycling
sequence
should
be
observed. Most types of unit malfunctions will
cause
a deviation
in this sequence
and
possibly a unit shutdown or a change in cycle
times.
When
the concentrator
is turned
on, this
normal cycling sequence should be observed.
A.
Right sieve bed is pressurized
(approxi-
mately 26 PS! (179 KPa)) and left sieve bed
is depressurized.
1.
Four-way valve is activated.
a.
Pilot pressure is entering four-way
(approximately 22-28 PS! (152-193
KPa)).
b.
A
12-15
VDC
signal
from
MC
board is present at terminals on
pilot valve and the green four-
way indicator
light is illuminated.
B.
Purging action is present (approximately
1.0 seconds) and bed pressures equalize at
approximately 15 PSI (103 K Pa).
1.
Purge valve is activated.
a.
Pilot pressure is entering purge
(approximately 22-28 PS! (152-193
KPa)
b.
A
12-15
VDC
signal
from
MC
board is present at terminals on
pilot valve for approximately
1.0
10/87
24
seconds
and
the
green
purge
indicator light is illuminated.
C.
Left sieve bed
is pressurized
(approxi-
mately 26 PSI (179 KPa)) and
right sieve
bed depressurizes to 2 PSI (13.8 KPa).
1.
Four-way valve is deactivated.
a.
The pilot valve shuts
off pilot
pressure to four-way.
b.
No voltage is present at terminals
of pilot valve and the green four-
way indicator light is not illum-
inated.
D.
Purging action is present as described in
step B.
E.
Step Ais repeated again.
NOTE:
Cycle
time
is approximately
11
seconds
for each
sieve
bed
at 2 LPM.
However increases in altitude and flow rate
will
increase
cycle
times
slightly
and
decreases will shorten cycles.
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