Repair of a Stuck CanoScan 4200F

Symptoms of the fault

1) The scanning unit with its light source, instead of being in its normal docking position, almost completely hidden underneath the grey plastic to the rear of the document glass, was visible, having been displaced some 25% towards the front

2) The Scanner made a “machine gun” like “clicking” noise whenever power was applied. With the document cover open, the toothed drive belt could be seen vibrating, but the scanning unit did not move

Cause

While scanning a large book, the document cover accidentally banged down on to the object being scanned.

Cure

With the scanner unlock switch at the bottom of the unit, in the “unlock” (padlock open) position…

A) The black plastic control panel at the front of the scanner was removed. This had to be done with great care not to strain the (very short and thin) ribbon cable connecting the left hand side of the control panel to the body of the scanner, and was done by…

a. Forcing the front edge of the control panel upwards (helped by a flat bladed screw driver) to release the clips under the SCAN and PDF buttons

b. Continuing to rotate the control panel upwards, hinging it about its top edge

c. Easing the clip protruding downwards from the right hand edge of the control panel towards the centre of the control panel (by poking it), and pulling the latch at the end of the clip out of the hole in the body of the scanner

d. Pulling the panel forwards a couple of mm to disengage the three clips sticking out of the top of the control panel

e. Pulling the left hand clip just clear of its hole in the scanner body

f. Rotating the control panel about the cable which still secured its left hand side, through an angle just large enough to reveal the opening in the scanner body

B) Inserting a long rod (a 30cm bamboo skewer from Morrison’s supermarket), through the hole revealed by the control panel, and pushing the scanning unit back some way towards the rear of the scanner

C) Plugging the scanner in to allow it to withdraw its scanning unit back to its normal position underneath the plastic

Related problems

Replacing broken tabs holding the scanner drive-belt tension-pulley, seemed to solve the problem in http://www.fixya.com/support/t440510-epson_4180_scanner_w_possible_drive_belt .

Lubrication seemed to solve a scanner “grinding” noise problem in http://www.fixyourownprinter.com/forums/inkjet/17222 .

Other people have described the same symptoms resulting from the spine of the scanner, or perhaps they mean the guide rail being bent, or the scanner glass becoming depressed and preventing the scanning unit from moving.

People have also described noises resulting from the scanning unit not being able to detect its docking position.

I tried, but failed to remove the glass and rear cover using the instructions at http://www.fixya.com/support/t14596635-clean_under_glass_canoscan_4200f .

There is an interesting service manual showing how the CanoScan 8000F works at http://www.prismpoint.com/servicemanuals/Scanners/Canon/Canon%20Scanner%20Canoscan%208000F%20Parts%20&%20Service.pdf .

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