Looking at the manual (update 93 software). It is in the Audio Alignment software tree just after BASS REP adjustment. You might need the 02/93 software to see it.

If your machine has older software (seen on the LCD screen when powering on), it might be a fixed value. If your machine isn't erasing, there's probably a failure somewhere else...

yes I have it on software menu, just how to set correct value? now is set to A4the machine is erasing but sometimes a very small signal is present....

Hi,which is the procedure to adjust erase current on a 2tk 1/4 A820 ? factory default value?thanks

I don't know the procedure for the 2-track. The brief time we owned a 1/4" 820, it never was an issue to address. On other machines, you record a lower frequency tone, then measure the output while erasing it, adjusting for a specified value. I don't recommend anything directly, since it needs to be specific to your machine. If, for instance the default value isn't doing it, and you crank the value to compensate, it could lead to worse problems. Sorry I can't be of much help.