If you don't have any wire to play, you can simply draw a thin bladed screw driver across the playback head while the unit is set to "play." It should make a popping noise in the speaker. A steel sewing needle will be just as effective. It is not wise to play wire on one of these units until it has been thoroughly gone over. The parts must be lubricated with precision, and the stopping brakes must work well. If they do not, when you stop the machine the spools of wire will continue to spin, and your music will be ruined in a tangled ball of wire. When working on a machine like this, it is best to use a spool of wire that you do not care about. Then, when you play pieces of interest after you have gotten it working, record them imediately on the first try (record onto CD or cassette or reel to reel). This way you will have the pieces recorded onto a less delicate medium. After they have been recorded, you may play the wire recordings as many times as you wish, and though it would be a shame if they tangled, you will not lose the music.
Thomas
P.S. There's a lot more to repairing the electronics of the machine than just the tubes, but the above source former will sell all of the components you will need.