Hi Justin,
The proceedure for erase depth adjustment is in the ATR102 manual PN 4890407-01 It is on page 5-39, is step by step and very well written. If you have a later -04 version manual, the procedure may be on a different page number under the maintenance section.
If you have done this procedure and you still have issues with erasure depth, please call me for tech support. 717-852-7700. Regards, Mike S.