Ralph Weldon, former administrator of Santa Anita Municipal Court in Monrovia, pleaded guilty to a misdemeanor charge of conspiracy to obstruct justice by canceling 73 traffic citations. Weldon, 34, will be sentenced April 24 by Los Angeles Municipal Judge Jacqueline Connor. Weldon resigned as court administrator in November after an investigation began into allegations of ticket fixing. Deputy Dist. Atty. Richard Healey said Weldon entered dismissal notations into computer records on traffic citations brought to him by friends and threw the citations away. Court officials said the people whose tickets were fixed will be notified that the citations are pending and added that $3,000 or more in fines could be collected.