Error 30 is "Skipped Index Pulse Error" related to the record magazine's optical switch. This means the computer was unable to tell the position of the record magazine because the magazine index pulse was not detected from the optical switches.
Causes could be dirty magazine gear (the optical switches need a clean gear to read the index position), a bad optical switch assembly, the optical switch connector may be dirty/unplugged at the mech control board, or you may need to adjust the mech control board index "I" trimpot .