The service manuel is very helpful, we where able to restore the device to its working operation again.
Text excerpt from page 70 (click to view)
Cleaning of Video Head
Clean the head with a head cleaning stick or chamois cloth. Procedure 1.Remove the top cabinet. 2.Put on a glove (thin type) to avoid touching the upper and lower drum with your bare hand. 3.Put a few drops of 90% Isopropyl alcohol on the head cleaning stick or on the chamois cloth and, by slightly pressing it against the head tip, turn the upper drum to the right and to the left. Notes: 1.The video head surface is made of very hard material, but since it is very thin, avoid cleaning it vertically. 2.Wait for the cleaned part to dry thoroughly before operating the unit. 3.Do not reuse a stained head cleaning stick or a stained chamois cloth.
Cleaning of ACE Head
Clean the head with a cotton swab. Procedure 1.Remove the top cabinet. 2.Dip the cotton swab in 90% isopropyl alcohol and clean the ACE Head. Be careful not to damage the upper drum and other tape running parts. Notes: 1.Avoid cleaning the ACE Head vertically. 2.Wait for the cleaned part to dry thoroughly before operating the unit or damage may occur.