Question about JVC HR-VP670 VHS VCR
I removed stuck tape in VCR and when I plugged it back in its stuck on rewind. Does not respond to any buttons I push.
... The takeup reel is turning properly but one of the reel rotation sensors or its electronics is defective. As a test, check to see if the tape counter is changing at any time during the loading and abort process. Non-real time tape counters usually get their pulses from this same sensor. Real time counters operate off of the A/C head control pulses and therefore would not be affected by a defective reel sensor). Some older VCRs used a belt driven counter - the belt may have broken or fallen off. Most newer VCRs use an optical sensor which may simply be dirty. See the section on: "Reel rotation sensors". 2. The roller guides are getting hung up and not fully loading the tape either as a result of an obstruction or dried up grease, or a slipping tape loading belt (often accompanied by an spine tingling squeal). Parts may have broken or fallen off of the roller guide assemblies preventing them from fully engaging the 'V-stoppers'. A similar fault may prevent the capstan from fully engaging against the tape d pinch roller. 3. The mode switch sensor is dirty or defective and confusing the poor microcomputer as to the position of the loading mechanism. In this case, the loading process may stop half way, pause, and then unload as in (1) or (2), above. Or, it may do almost anything. See the section on: "Erratic behavior in various modes". 4. Some other condition such as the end-of-tape sensor thinking that you are at the end of the tape is aborting the tape loading process. This might be indicated by a sudden reversal and shutdown rather than a pause (usually accompanied by the sound of a motor whirring) at some point attempting to complete part of the cycle. For problems with record in particular, the record protect tab switch may be dirty or worn resulting in random aborts. 5. Electronic problems like bad grounds or other bad connections are alos possible. Since with some models, (a number of JVC manufactured VCRs, for example) ground integrity is via screws through the mainboard, should these loosen, erratic behavior may result. Tighten the screws. 6. A defective microcontroller or other logic could also be at fault but this is less likely than any of the preceding.
Posted on Nov 29, 2005
This is a problem with the process called 'tape loading' - pulling the tape loop out of the cassette and wrapping it around the spinning video drum, engaging the capstan and pinch roller and reel rotation. Check all the belts above and below the deck. Belts can appear to be firm but if they do not return immediately to their relaxed length when you stretch them 25%, they will need to be replaced. With the cover off, observe the behavior when you hit play. (You may need to put a piece of cardboard over the cassette to block external light from interfering with the start/end tape sensors). Assuming this is a basic VCR (no instant start features), you should see: 1. The video head drum begins to spin. 2. the roller guides move smoothly on the tracks, wind the tape around the drum, and stop snuggly pressed against the 'V-stopper' at the end of the tracks. 3. The pinch roller moves into position and presses the tape against the capstan. 4. The tape begins to move and is wound up by the takeup reel. 5. The picture and sound appear on the TV. With a 'rapid or quick start' (or it may be called something else) transport, the tape moves to a half-loaded position when the cassette is inserted. This is at an intermediate position partially pulled out of the cassette but not wrapped around the drum. On VCRs with a real-time counter and/or index search capabilities, the tape will be in contact with the control head. With an 'instant start' transport, the tape will fully load around the spinning drum when the cassette is inserted but the capstan will not engage and no tension will be applied to the tape until you press PLAY or REC. (After about 5 minutes, the drum will stop and it may unload to the half loaded or unloaded position.) Note that for VCRs with a real-time counter and/or index search capabilities, the tape must be in contact with the control head (but not the video heads) for all relevant modes. These VCRs (which include many modern units) must therefore pull the tape at least partly out of the cassette. In all cases, the completion of the sequence results in approximately the same mechanical configuration during PLAY. Several likely possibilities when it shuts down: 1. Everything occurs as above, picture and sound appear for a few seconds, but then the VCR unloads the tape, ejects the cassette, goes into REW mode, stops, or shuts off. Two common causes: The takeup reel does not turn and tape spills into the machine. This is sensed by the microcontroller which aborts record or play and attempts to save your valuable cassette. Most likely cause: old/dirty idler tire. As a test, turn the idler tire inside-out. The fresh surface will now work well enough to confirm this diagnosis and will continue working long enough for your replacement idler tire to arrive. See the section: "General guide to VCR cleaning and rubber parts replacement". The takeup reel is turning properly but one of the reel
Posted on Nov 29, 2005
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