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Super fast REW or FF on VCR, problem, Sharp VC MH711

Will rewind 90 percent of a 4 hour tape in 40 seconds or so and 20s for the remainder. What would allow the motor to run at full tilt ? clunking loudly to a stop. If it was not for the "crumple zone" of tape pulled into the gap between tape roll and spool disc then the tape would have snapped at the end of tape. What to look for in the way of a problem ? System presumably monitors ratio of supply and take up rotation rate and direction of wind and unlaces tape from drum and over 3 stepped increases , sets at maximum revs until the ratio goes over a preset value and drops by stages to a slow rate until end of tape sensor acts.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook
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I'm not exactly sure what you're saying is the fault. Is it that the motor is going too fast and/or it is making a clunking noise near the end of the tape? Newer VCR's do bump up the rewind speed after several seconds to but I think you know that already. Is the machine damaging the tape?

-- David Farber David Farber's Service Center L.A., CA

Reply to
David Farber

increases

by

I

It should recognize getting close to the end of tape and start reducing the power / revs of the motor but it once continued at full revs to the end of tape. Been monitored by human since it happened. It does not speed up if human stops the motor close to end, goes normal speed to the normal clear tape auto stop if REW is engaged again ofter pre-emptive stop.

I'm thinking a break in the line from the fast , take up spool sensor, so less pulses coming from it and false interpretation.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook

Does the same thing happen when you fast forward to the end of the tape?

--
David Farber
David Farber\'s Service Center
L.A., CA
Reply to
David Farber

Taking the cover off and visually monitoring the amount of tape left, the VCR works fine FF or REW . Going up to express rate and back down , in either direction, as long as there is plenty of tape run.. It just once , so far, spectacularly failed.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook

this is almost certainly something to do with the A/C head. I suspect the deck reads the timecode pulses off the control track and stops or slows down according to the tape position as deduced from this (many vcr s have a 'goto' function which locates a point in time on the tape you can enter in hours/ mins).

chances are, the tape in question may have had edge damage, or there was dirt on the Ac head which messed up the signal. B

Reply to
b

Very unlikely, a blank tape has no control signal. The OP ought to scope T and S reel signals all the way to the micom.Dirty optical pattern on the reels maybe?.

Reply to
jango2

Are your tapes that impotant to you? If it only does it once in a blue moon, who cares?

P.S. mine (a Samsung) does the same thing about 1 in 30 times, but 20 minutes from the start of the tape. It appears to panic thinking it's about to hit the end and had forgotten to slow down. It goes straight from full speed rewind to stop, and I have to press rewind again to rewind the remainder of the tape.

Nevermind, once I've watched my backlog of tapes, I'll be giving it away. I've got a Sky HD box (built in hard disk recorder) which I upgraded to a terrabyte :-)

--
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Reply to
Peter Hucker

I've seen that with these short length tapes that have big reels. The VCR always thinks they are in the middle and FF and REW full speed the entire tape. Philips VCRs trigger their brake when the end sensor detects end of tape, avoiding a possible tape break.

Reply to
Jeroni Paul

the

stop.

Not played up since, perhaps 20 FF REW runs. Including using a new tape so no timecoding. Perhaps just a spec of dust to jump into an opto gap at the wrong moment is all that is needed.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook

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