Recently I've had to learn some command line SVN rather than using GUI interfaces like TortoiseSVN. I'll try provide some little tips to find the logs of a repository.
Above : The command to show all the revisions that affect the folder you are in. If you have too many revisions, you're command line interface may not be able to show all the revisions due to memory size. Also, it may not show the head revision because the directory you are in might not have any changes in the head revision.
Handy Log Command - Show the last x Number of logs
svn log -r HEAD:BASE -v -l 10
Above : This will show the last 10 revisions of the complete repository (if you are running the command in the root directory. If you want to show more change the number 10 to the amount of results, or if you want to show all the results, just remove the -l 10. -r HEAD:BASE means it is showing from the head revision to the base revision, -v is verbose meaning it will show more information about the log such as the files that were changed in the revisions.
Get Stuck? Use the help
svn log -h
Above : If you want to see the documentation provided by subversion to help you out, just use -h to display the help text.