Resolution:
CAUSE: The ribbon motor may be installed with incorrect orientation, allowing the wires to the ribbon motor to come in contact with shuttle leaf spring. This will result in the insulation fraying, followed by shorting the motor drive power to ground through the spring, damaging the TTMI board ribbon driver transistor.

Underside Of Ribbon Deck:

ACTION: Inspect the ribbon deck as follows:

Turn the ribbon deck upside down with the fans to the bottom.

Note whether the ribbon drive motor wires CORRECTLY enter the motor case from the top, that is the side opposite the fans. If so, note that the wires are correctly routed from the motor straight upward and into the plastic channel and under the foam padding. Further note that the wires CORRECTLY travel within the channel, staying under the foam, until they reach the interface connector.

If the motor has been oriented such that the wires INCORRECTLY enter it from the left, that is from the side facing the interface connector, they are subject to being chaffed and shorted by the shuttle spring. Correct the orientation of motor, repair any damaged wires and route them correctly. Otherwise replace the motor.

If not detected, the shorting will eventually cause the ribbon motor drive IC to overheat to the point of destruction. Replacing the board may appear initially to solve the problem. We have seen one case in which the replacement TTMI board lasted about three weeks.