[TimeBandit]

I recently changed the drawer loading belt on a 5500, and all was fine at first. Now, however, I’m getting this squealing noise after the drawer closes. I’m pretty certain it’s the motor still turning even though the drawer has fully closed. And, in fact, I monitored the voltage and see that the motor is still receiving around 13V during the time that it should have stopped. Has anyone else encountered this? It seems as if whatever signal (from a leaf switch?) that should tell IC9 that the drawer is closed isn’t getting through.

[Mark-sf]

There is no switch involved. The direction and action is controlled by two pins, 21 and 22 on IC8 that provide a differential voltage to dual op-amp IC9. I do not have access to the service manual that may explain how end of travel is sensed.

[Dillen]

Mark-sf wrote:

There is no switch involved. The direction and action is controlled by two pins, 21 and 22 on IC8 that provide a differential voltage to dual op-amp IC9. I do not have access to the service manual that may explain how end of travel is sensed.

It’s not.
The motor runs for a preset time.

Martin

[Mark-sf]

Thanks Martin. This then means you need to check how long those pins are active in each direction. If the go back low once the drawer closes then I would look at the OpAmp driver circuit to see if there is a bad cap for example that is keeping the output latched.

[TimeBandit]

Martin: Do you know what that preset time would be?

[Mark-sf]

TimeBandit wrote:

Martin: Do you know what that preset time would be?

This time is not adjustable and is only a few seconds sufficient to close/open the drawer. The issue is that the motor should not be continuing to run. Since it is seeing 13v when closed, the OpAmps are active. Since the drawer does open and close, the signals from the two pins of 1C8 are working, but may not be resetting.

[Jerryege]

Morning Martin,

I am having the exact same issue. How can it be resolved? do i need to replace or check capacitors or an IC chip?

[Author]

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