Adat noises??????

[voodoo101]

Every now and then it seems that my ADAT makes a terrible sound. I have three adats and during playback it made a terrible sound...sort of like ckkskkskskkkkkshkkk. It occurred on the same channels at the same time..so it was not random. I didnt hear it during tracking...just playback. It was like it was recorded to tape that way. Do they need cleaned? I'm new to this(and bought them used from a GOOD source) so I think they need there heads clened? am I far off the mark? If they do need cleaned, is there a head cleaner out there for the maintenence....like cassettes have?