Lazarus Cascade Basic Preamp - Tube question

I have a Lazarus Cascade Basic tube preamp without a manual. It has 4 12AX7 tubes mounted horizontally from left to right facing the front of the unit. I want to change just the line stage tubes, but not the phono tubes. Do you know how I can tell which tubes to change? Thanks for any info or assistance you can provide.
Sorry, but it has been too long since I had one open to be sure of the configuration. Usually, the tubes for the phono stage are the tubes closest to the input "phono" jacks on the rear panel, if this is of any help. Good luck.
What tubes are in it now? Appearantly you have not tested them. It appears that you don't want to use the phono stage. If that assumption is true, you can see if the phono tubes are stronger (which they probably are). If that's true, just switch them.

If you can't find out which tubes do what, just swap the left and right pairs-WHILE THE UNIT IS OFF. This might be all you need to retube your unit.