Hello Ignacio and welcome to Electronics Point.
I have fixed your post. Please observe the following rules - they are standard for all forums on the Internet.
- Don't post a new subject on an existing thread. This is called "hijacking" the thread. If you have a new question, start a new thread.
- Post in Mixed Case, not ALL CAPS. On the Internet, ALL CAPS is considered to be SHOUTING.
- Post your question ONCE only.
I have looked on the best service information site that I know of,
http://www.elektrotanya.com, and there were no matches for Digitech RDS1900.
Have you tried a thorough Google search? You should always do this first, before you ask your question in a forum. Go to
http://www.google.com and enter the keywords Digitech RDS1900 RDS-1900 schematic service manual.