Below is a good tip from LeCroy scope user Joe who did not have a GPIB card to reset the serial number in his scope. This technique should work for a 93XX/LC/LT (WR1 and WR2 and WP) scopes. It just requires a null modem cable. 

The command is (Exactly as shown)

$$SY_NO XXXXX

Note: There is a space after the NO. The XXXXX represents the digits on the serial number 
plate on the rear of the instrument. The digits entered must exactly match the plate digits!

The text below is verbatim for Joe:

"I just finished resetting the serial number in my 9374. I didn't need to use Scope Explorer or HP-IB.  I connected the 9374 to my PC with a null modem cable (used a double headed serial Lap Link cable actually) and used the Hyper terminal program that came with Win XP.  Just set the settings in the terminal program and on the 9374 to match (I used 8,1,none and 115,something baud). I typed in the serial number command EXACTLY as your message said and it worked.  I found that you can use up arrow and go back to previous command and use it unchanged or edit it and press Enter to resent it. It sends the command BUT the scope rejects it if you do it that way. ????  You need to retype it every time! Also the scope rejected it if it wasn't on the normal Display screen! It will not work if you have the status screen displayed! Just press Display then send the command it will work."

Thanks Joe,

Sam
Moderator