1.You can use login name:mac and password is the MAC address of your 3502A to enter the machine. You can saw your MAC address under the machine. 
2.You can change the password by enter the boot mode. Below is step by step to told you how to enter the boot mode.
First,turn off(unplug) the power. Connect 3502A with the console port and open the HyperTerminal. Now turn on power supply of Wellgate 3502A. You will see the following display from HyperTerminal display of your PC.
 
Attached TCP/IP interface to cpm unit 0
Attaching interface lo0...done
Please wait while system is initializing ..........         ----> press enter within 3 seconds. 
 
Now it is in BOOT MODE. 
 
boot line : cpm(0,0)host:vxWorks h=192.168.4.109 e=192.168.201.201 u=vwusr pw=vw
usr g=192.168.1.254

login    : water

password : 3333
 
[help] , list all boot commands
BOOT> h

 b                     - program boot sector
 c                     - change network address
 d                     - use tftp download file
 f                     - input tftp file name
 g                     - go to ap
 m                     - modify mac address
 p                     - program ap sector
 r                     - reset
 s                     - show current network address
 w                     - password set
 x                     - show BOOT and AP version
 z                     - program 2M rom file
Press W to change the password
After changed your password, press "r" to reboot the machine.
Now you can enter 3502a with new password