The tape heads of any reel to reel machine can be the most expensive part to replace and therefore it's important to know if they are worn before purchasing any machine. 

 

The images on this page give some example of heads that are worn.  Some tape heads can be serviced, known as re-lapping, essentially this removes some of the head surface to create a new and smooth and correctly profiled path for the tape. 

 

Why do tape heads wear? 

 

Magnetic tape is slightly abrasive and will in time wear away the surface on the head and tape guides, this can often be seen as a slot in the head face.  Provided the tape runs nicely in the slot then this wear does not present too much of a problem, although the tape will tend to catch on the sides of the slot and result in the tape breaking contact with the recording ‘gap’ and cause drop out; careful re-lapping can often be effective in removing the sides of the slot and result in much improved performance. 

 

Unfortunately at some stage, the wear on a tape head can be so great the recording ‘gap’ will open up and no amount of re-lapping will extend its life, indeed re-lapping may result in a head that was just about usable, being written off, it's therefore important that those who service machines to recognise the limits.      

 

Many Sony and Akai machines use heads made of ferrite and other very hard materials so don’t wear, although Sony and Akai heads do, from experience these suffer failures if they have been stored in damp conditions, as they seem more prone to corrosion.

 

Revox heads have slots cut each side of the tape path during manufacture, specifically to avoid a slot being created by tape wear; the tape contact area is effectively raised.  As a general rule the head is still usable until the tape has worn the raised area down to the floor of the slots, although on occasion the edges of the tape run area starts to break up before this stage is reached, resulting in very evident drop out.