no easy answer....
1) How does customer know the head is bad? It is not always easy to determine.

2) The cost of replacing ONLY the head is $635.00. The problem here is that you almost always have other pieces-parts which have worn along with the head. There have also been several transport upgrades over the history of the unit.

Tascam has a Transport Exchange Program:
A factory rebuilt/updated transport is available. Everything which is worn is replaced and all upgrades are installed.
The transport is a self contained module. Removal and installation is with screws and push-on connectors (no soldering or alignment is required).
A 'techie' customer can exchange one himself, directly with Tascam. Final cost to customer is about $520.00. There is a refundable $800.00 core deposit. You ante up, Tascam ships the refurb transport and you return the defective, IN THEIR SPECIAL SHIPING CARTON, and Tascam refunds the deposit.

We sell the refurb transport for $625.00 + $90.00 labor (to determine the head is bad and install the refurb transport.)

Bottom line; If the head is bad, buy a refurb transport....