DR5000 Chart Does Not Show Correct Time after Chart Change

Brief description of how the chart drive motor works and how to tighten the chart retaining hub is shown below with a graphic showing a typical chart with the correct time initially not being shown after chart change.

 

How the Chart Drive Functions:

The motor and gearbox work together as the “chart drive system”. The motor is the timing mechanism. The gearbox adds the necessary “mechanical” torque required to turn the chart without stalling the motor. The motor alone does not have enough torque to turn the chart paper.

 

Impact of incorrectly tightening the Chart Retaining Hub/Nut:

If the chart retaining hub/nut is incorrectly tightened the chart gears will exhibit "backlash" and initially after chart change the chart will not rotate with the configured time until the gears "mesh".

 

The chart spindle (shown within the pdf document) that the chart paper sits on must be allowed to turn when the chart knob is tightened so that all of the “teeth” of the gears in the gear box are meshed together. Holding the paper prevents this from happening. The chart spindle doesn't begin to rotate until all of the “teeth” of the gears are touching. There are 4 gears in the gear box (with a 600 to 1 gear ratio). This means the motor has to turn 600 revolutions for the chart spindle to turn 1 revolution. There could be as much as a 3 hour delay before the chart spindle begins to turn if there is a gap between all of the “teeth” of the gear.

 

How to incorrectly & correctly Tighten the Chart Retaining Hub/Nut (correctly tightening eliminates gear "backlash"):

• Incorrect Method: Holding the paper with your finger while tightening the chart hub/nut (do not do this).

• Correct Method: Do not hold the chart while tightening the chart retaining hub/nut and allow the chart to turn slightly when the knob is tightened. Position the paper knowing that the chart may turn slightly so that when the knob is tightened, the slight turn of the chart will align the pen with the correct time on the chart. If the pen is no longer starting at the correct time, then loosen the knob, re-position the chart and start again.

  Turn Chart Hub/Nut Clockwise only: make sure chart hub/nut is only turned only in a clockwise rotation to secure chart paper. Rotating the knob counter-clockwise after the knob has been tightened will introduce “backlash” into the gearbox and will appear as if the chart is losing time similar to holding the chart paper while tightening the chart retaining hub/nut.

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Sample Chart with chart drive exhibiting "Backlash" due to holding the chart in place while tightening the chart retaining hub/nut resulting in the chart does not initially rotate with the time.