On a VCR with autotracking, the autotracking light may be flickering as well.
Possible causes for loss of lock:
- Dirt or bits of tape or oxide on control head - clean and inspect.
- Defective control head. Try making a recording. If recording plays normally on another VCR, then control head is probably OK.
- Tape wandering up and down so that control track is not sensed properly (how is the sound - this would also cause fluctuating or missing sound.) See the section "VCR randomly switches speeds, tracking problems, and muddy sound".
- Mechanical fault preventing firm tape-control head contact such as a stuck movable guide post.
- Mechanical or mode switch problem preventing firm capstan-pinch roller contact. Under certain conditions - possibly at the beginning of a tape when takeup tension is greatest - the takeup reel may have enough torque to pull the tape past the video heads without the capstan controlling the speed as it should.
- Defect in servo or control circuitry or power supply (voltage out of tolerance).
This someone unusual possibility deals with the case where a tape can't be viewed properly using the same VCR on which it was recorded.
For 2 head VCRs:
- Where playback of self-made recordings is bad or noisy (but they play fine on another VCR) and known good recordings made on another VCR play fine on this VCR, the video heads may be worn to the point of being marginal. Since the signal goes through the same heads twice (once for record and once for playback), any signal degradation will be worse.
For 4 (or more) head VCRs:
- In addition to the possibility, above, record and playback may use a different set of video heads and the playback set may be dirty, worn, or damaged. In this case, a recording made on a known good VCR at the same speed should also not play back properly.