DeVilbiss 525 Series Service Manual download pdf (Page 18)

LT-2023

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,

theunitmustrun20minutesbeforethepowerfailalertwillbe

enabled. This alert is powered by a capacitor on the PC board.

CAUTION– DonotapplyanyforceorextothePCBoardwhen

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–ConrmPCBoardiscorrect;useonly525DS-622on525DS

unitsand525KS-622on525KSunits..

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

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:

NOTE–The2-3Voltreadingwillgoonandoffasthevalve

cycles.525Serieshaveaxedcycletime.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.

COMPONENT TESTING, REPAIR, AND REPLACEMENT

Negative Lead Positive Lead Voltage Reading

Orange Yellow or White 12 VDC

Orange Gray 5 VDC

Orange Brown 5 VDC

(intermittent)

Black or Green or

Red or Blue

Yellow or White 2-3 VDC

(intermittent)

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 43 44

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DeVilbiss 525 Series Service Manual Page 18

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