Turns out this was not the manual i was looking for. The concertmate 670 keyboard i have is a "Realistic" model made for Radio Shack and none of the diagrams on the owners manual i received matches up. HOWEVER, I must say the service Owners Manual provides was fast and efficient by being available online. The manual was in good readable condition and easily downloaded.
Thank´s for your help, I already recived these manual from you
Text excerpt from page 34 (click to view)
Installation
Inserting the non-return flap Attaching the motor assembly
^ Air extraction: If a non-return flap is not present in the venting system, the non-return flap supplied must be fitted into the exhaust connection on the motor. The flaps must open upwards. ^ The hood is designed for 6" (150 mm) exhaust ducting. If 5" (125 mm) exhaust ducting is used the reducing collar must be fitted into the exhaust connection on the motor (see "Air extraction"). ^ Recirculation mode: The non-return flap is not required.
^ First loosely screw the two locking nuts onto the threaded bolts on retaining plate A. Leave a gap of 1/ " (3 mm) for
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hanging the motor on.
^ Fit the motor assembly onto the hooks on retaining plate A and slide down behind the nuts. ^ Tighten the nuts.