Problem with tape importation - possible tape speed issue?

I have a Canon HV10 - an HD 1080i to miniDV tape camcorder that at one point a couple years ago got "out of adjustment" such that tapes could not be played back. I sent it in for service to Canon and was told the heads were dirty though I had at that point used it very little. It seemed to work fine once back and could be used to playback tapes before and after the "out of adjustment" period. The problem is that I have 3 tapes with data on them which I would very much like to access (kids were at a very cute age) and I know the data is there. I know this since when playing back these tapes the unit shows blue screen only BUT when fast forward is pressed during playback it behaves as it would with any other tape - jittery, fast moving images without sound are seen. I assume this means the camera record speed was slightly off during that time. I have since upgraded to another camera (a Sony) and I'm willing to "experiment" with any recommended adjustments to see if I can rescue these movies. Any help appreciated!