Printed Circuit Board (Pc Board); Rotary Valve; Sieve Bed Check Valves - DeVilbiss 525DS Service Manual

c o M P o n e n T T e S T i n g , r e P a i r , a n D r e P l a c e M e n T
To replace the pressure regulator (Figure 9):
1. Make sure the unit is unplugged from the wall outlet.
2. Remove the front and back cabinets.
3. Remove the tubing clamp and tubing from the pressure regulator.
4. Unscrew the regulator from the accumulator tank.
5. Install a new regulator on the accumulator tank and attach the tubing
and tubing clamp.
6. Replace the front and back cabinets.
PrinTeD circuiT BoarD
The printed circuit (PC) board is responsible for monitoring and
controlling the DeVilbiss Oxygen Concentrator.
The PC board has preset alerts for low flow and power failure. Should
any of the alert values be exceeded, the patient alert system will activate.
noTe–
If the concentrator has been unused for an extended period,
theunitmustrun20minutesbeforethepowerfailalertwillbe
enabled. This alert is powered by a capacitor on the PC board.
cauTion– DonotapplyanyforceorflextothePCBoardwhen
connecting or disconnecting electronic or pneumatic
components. Damage to the electronic assembly is
possible.
To remove and replace the Pc board (Figs 5 & 7):
1. Make sure the unit is unplugged from the wall outlet.
2. Remove the front and back cabinets and the bib.
3. Disconnect all wires, terminals and connectors.
4. Remove the 1/8" (3.2mm) tubing attached to the sensor.
5. Remove the screw that secures the board to the unit and remove
the PC board.
6. Install the new PC board and secure it using the screw.
noTe–
 C onfirmPCBoardiscorrect;useonly525DS-622on525DS
unitsand525KS-622on525KSunits..
7. Reconnect all electrical wires, terminals, connectors and the tubing
to the sensor.
8. Replace the bib and front and back cabinets.

roTary valve

The timed rotary valve alternately distributes pressure supplied by the
compressor to the sieve beds. While one bed is being pressurized the
other bed is being exhausted through the valve. Exhaust gases go through
the valve exhaust port and exit through the exhaust muffler.
The valve contains two revolving discs powered by a stepper motor to
cycle the pressure between the beds. DC voltage is supplied by the PC
board to the motor windings causing the internal discs to turn and direct
pressure to the proper sieve bed.
If the rotary valve does not shift properly the same bed may continue to
pressurize causing the pressure relief valve to release the excess pressure.
There are several reasons why the rotary valve could malfunction;
therefore the cause of failure must be determined before corrective
action can be taken.
To test the rotary valve (Figures 9 & 16):
1. Remove the front cabinet.
2. Connect pressure gauges to the test points at the top of the sieve
LT-2023
beds in order to observe unit cycling and bed pressures. Refer to the
section on Normal Operating Sequence.
3. If it is determined that the valve did not shift properly or the bed
pressures are uneven, continue testing with step 4.
4. The stepper motor on the rotary valve has multiple windings so
there are several voltage readings that need to be checked in order
to determine if the problem is being caused by the PC board or the
valve itself. Testing for proper voltage is done at the wire harness
connectors on the valve or on the PC Board using a voltmeter.
Below are the valve voltage test positions and voltages that should
be present at each one:
negative lead
Orange
Orange
Orange
Black or Green or
Red or Blue
noTe–
 T he2-3Voltreadingwillgoonandoffasthevalve
cycles.525Serieshaveafixedcycletime.However,
when the concentrator goes into its "turn-down" mode,
the cycle time is shortened.
5. If any of these readings are not obtained, check for loose or broken
wires in the harness. If wire harness is okay, replace the main PC
board.
6. If proper voltages are obtained, replace valve.
To replace the rotary valve:
1. Make sure the unit is unplugged from the wall outlet.
2. Remove the front cabinet and loosen the bib.
3. Unplug valve wire harness from the valve.
4. Loosen speedy clamps and remove bed hoses from each side of
valve.
5. Loosen ladder clamps and remove pressure intake and exhaust hoses
from backside of valve.
6. Install the new rotary valve by reversing the above procedure.

Sieve BeD cHeck valveS

A check valve (Figure 6) located between the outlet of each sieve bed and
the accumulator tank allows oxygen to pass through the sieve beds to the
accumulator tank when the bed pressure is greater than the accumulator
tank pressure. These valves also prevent reverse flow of oxygen from the
accumulator to the sieve beds.
Run the Accumulator Pressure Test described in the Component Testing,
Repair, and Replacement section. It covers details of attaching the gauge.
Acceptable pressure swing ranges at various altitudes are included in the
Specifications.
A defective check valve will result in a decrease in oxygen concentration
and lower accumulator pressures.
To replace a defective check valve, remove the tubing on either side of it
and install a new valve making sure the outlet end is toward the
accumulator tank.
18
Positive lead voltage reading
Yellow or White 12 VDC
Gray 5 VDC
Brown 5 VDC
(intermittent)
Yellow or White 2-3 VDC
(intermittent)