641 Chair Back Up / Down Function Troubleshooting
This illustration shows only the components that affect the Back up / down function. Refer to:Back Up / Down for a detailed description of Back up / down operation.
Only the wires that affect the Back Function are shown.
•Black and white wires supply 48-54 VAC to power the Base and Back actuators.
•If Power Light is on, proper voltage is present at PC Board.
•If Power Light is off, Refer to: Power to the Table for troubleshooting.
On models w/ rotational base, the Main System Transformer connections are supplied thru the Rotational Base PC Board - not shown.
Is There Power To The Table?
When voltage is present at the PC board, the power light is illuminated.
Refer to: Power to the Table, for description of current flow to the PC board.
Power To Foot / Hand Controls
Circuitry on the PC board supplies 8-10 VAC to the hand / foot control connection ports.
Refer to: Crash Avoidance System for a detailed description of crash position, and the table functions that are disabled.
Backup Operation
When the Back Up function is activated, current flows thru the hand / foot control, back to the PC board. Circuitry on the PC Board supplies approximately 48 VDC to the back actuator motor.
The PC board continuously monitors the Back Up limit switch and the Back position sensor. If the Back Up limit switch is tripped (closed), the Back Up function will not operate. If the Back position sensor detects that the back section has reached its upper limit, the Back Up function will not operate.
The actuator motor runs and raises the back section.
Actuator Motor runs until:
1.Hand / foot control button is released.
2.Back Up limit switch is tripped.
3.Emergency Stop button is pressed.
4.Position Sensor detects upper limit.
5.Overcurrent protection tripped.
6.Software time-out limit is reached, approximately 30 seconds.
Back Down Operation
When the Back Down function is activated, current flows thru the hand / foot control, back to the PC board. Circuitry on the PC Board supplies approximately 44 VDC to the back actuator motor.
The PC board continuously monitors the Back Down limit switch and the Back position sensor. If the Back Down limit switch is tripped (open), the Back Down function will not operate. If the Back position sensor detects that the table is in a potential crash position, or that the back section has reached its lower limit, the Back Down function will not operate*.
The actuator motor runs and lowers the back section.
Actuator Motor runs until:
1.Hand / foot control button is released.
2.Back Down limit switch is tripped.
3.Emergency Stop button is pressed.
4.Crash Avoidance System activated*.
5.Position Sensor detects lower limit.
6.Overcurrent protection tripped.
7.Software time-out limit is reached, approximately 30 seconds.
Problem: No Back Up or Back Down.
1.Loose / Damaged Wire Connections - Back Actuator, Back Up/Down Limit Switches, hand/foot control ports, black and white wires between main system transformer and PC board.
2.Hand / Foot Control Refer to: Hand and Foot Controls
3.Back Actuator / Limit Switches Refer to: Back Actuator and Limit Switches
4.Main PC Board Refer to: Main PC Board
Problem: No Back Up, Back Down OK or No Back Down, Back Up OK
If Base Down is inoperable, move the chair functions Base / Foot to full Up position and the Tilt to full Down position. If Back Down function becomes operable, Refer to: Crash Avoidance.
1.Loose / Damaged Wire Connections - Hand/Foot Control and Back Up / Down Limit Switches.
2.Hand / Foot Control Refer to: Hand and Foot Controls
3.Back Actuator / Limit Switches Refer to: Back Actuator / Limit Switches
4.Main PC Board Refer to: Main PC Board
Problem: Back drifts down and/or Noisy operation Grinding / squeaking
1.Back Actuator Refer to: Back Actuator / Limit Switches
Problem: Moves slowly and/or Will not lift patient
1.Did patient exceed 450 lb. weight limit? Inform staff that max. patient weight is 450 lbs. Refer to: Specifications
2.Low voltage to table
| Required Voltage | |
|---|---|
| 115 VAC models | 115 +/_ 10% VAC |
| 230 VAC Models | 230 +/- 10% VAC |
3.Back Actuator Refer to: Back Actuator / Limit Switches
Problem: Back Up and/or Back Down moves briefly, then stops "beeps"
Before performing any of the checks on this page, move the chair functions Base / Foot to full Up position and the Tilt to full Down position. If Back Down function becomes operable, Refer to: Crash Avoidance.
1.Calibrate PC Board Refer to: Main PC Board
2.Loose / Damaged Wire Connections - Back Position Sensor, Hand/Foot Controls
3.Back Position Sensor Refer to:Position Sensors
4.Back Actuator Refer to: Back Actuator / Limit Switches
