Exactly what will show for terminal 13 will vary from meter to meter. It should not read 0, so check your soldering carefully on both holes of 13, and any holes at the other end of any wires or components attached to 13.
Center pins of RCA jacks being grounded will result in a VERY quiet amp. Does it read zero regardless of position of the volume pot? Also check closely for something physically on the jack - looking at the bottom side of the jack, you can see a small gap filled with white plastic. If a small glob of solder happened to fall on that gap, the input would be shorted. Incorrect installation of the jack will also cause problems, make sure the washers were installed exactly as shown on page 11, and make sure the shoulder washer is properly seated with its ridge resting in the hole and the flat portion sitting flat against the chassis.
