VCR has issues playing certain tapes.


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VCR has issues playing certain tapes.

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philinchio
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Mar 7, 2010, 8:15 AM

Post #1 of 4 (1804 views)
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VCR has issues playing certain tapes.	Can't Post

I have a JVC Pro-Cision 19u Head which is having problems playing certain tapes properly and I'm not sure whether it's due to the tape wearing out or the heads not lining up properly.
It will usually play regular movies (like Disney for example) without problems, but the main issues happen with recordable tapes. They are almost always in EP mode when this happens.

I put the tape in and it will play normally for a few seconds, but then the counter which records and displays the run time stops recording the time. The tape continues to play, but then the picture starts getting fuzzy on the bottom part of the screen, slowly progressing upwards until it fills the screen and then it switches to a blue "auto picture" type screen for a few seconds before displaying the video again and the pattern keeps repeating.

Occasionally the timer will suddenly begin recording the run time again, sometimes stopping shortly thereafter or continuing for the remainder of the tape. When I fast forward the timer will also exhibit similar behavior, recording the time and then stopping only to start back again. Rewinding will record the time no matter what. It will do this with certain tapes but sometimes work fine with other recordable tapes.

The same tape will play on my parents' combo DVD-VCR player without any timer or picture issues at all.

I'm not sure what to do. I've cleaned the heads with special tape and that hasn't solved the problem. I'm considering taking it to a shop that specializes in VCR repair but I'm still not sure whether something in the heads is mis-aligned or if one of the magnetic sensors is malfunctioning.

Hopefully someone here can answer my problem.

(This post was edited by philinchio on Mar 7, 2010, 8:35 AM)

techchris
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Mar 7, 2010, 3:20 PM

Post #2 of 4 (1797 views)
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Re: [philinchio] VCR has issues playing certain tapes. [In reply to]	Can't Post

probably the pressure roller is worn unevenly,pulling the tapes off alignment.Take it out the machine and check it against the straight edge of a rule to see.If you take the top off you will see the rubber roller to the right of the headdrum.

jts1957
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Mar 7, 2010, 9:00 PM

Post #3 of 4 (1795 views)
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Re: [philinchio] VCR has issues playing certain tapes. [In reply to]	Can't Post

Sounds more like a Capstan servo problem. Bad electrolytic in that circuit or in the power supply sources that power same circuitry. Smile

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Barry777
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Mar 11, 2010, 1:57 PM

Post #4 of 4 (1783 views)
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Re: [philinchio] VCR has issues playing certain tapes. [In reply to]	Can't Post

With any GOOD VCR (manufactured before 1990), my first step is always to recap the power supply board - this fixes a lot of problems before I touch any adjustments, etc. Especially with switching-type or resonant-mode power supplies, cap values are very important as they are parts of oscillators rather than acting as simple filter like in the old fashioned transformar/rectifier/filter arrangement.
The faulty caps are usually not the largest ones; from my experience the ones that are low cap/high volt (such as 1 uF at 50 volts) are the first ones to break down. I would replace all the smaller ones, then move on to the bad boys if that doesn't fix the problem.
True, it could be a capstan servo issue - but it's more likely to be caused by the power supply than in the capstan servo system itself. I would think a worn pressure roller would also cause trouble on the other speeds, but it is a possibility as the EP speed is the most critical. If there's a seperate capstan free-run adjustment for EP speed on the circuit board, might try slightly adjusting that AFTER replacing the power supply caps. Not a good idea to mess with adjustments before recapping, or you'll end up with a machine with good caps but is now out of alignment.
If you're not into electronics, it's best to let a professional handle it - this isn't dirty heads or anything else that can be tackled the layman or a few pieces of test equipment. If you know an excited kid with a soldering iron, he can probably replace the caps - but I wouldn't go any further than that.
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Barry Fone - VCR Repair hobbyist and professional FAA Repair Station Avionics Bench Technician (top level). TEST EQUIPMENT: (4) Sencore VC93 VCR Analyzers, (11) Tentel gauges, Sencore VA48 and (2) VA62 Video Analyzers, Sigma Electronics TSG-375 NTSC/SMPTE Video Generator, several VCR Alignment Tapes, plus countless Oscilloscopes, Frequency Counters, Wow and Flutter Meters, Distortion Analyzers, Vectorscope, 136-channel Logic Analyzer, Signature Analyzer . . . . VIDEO GEAR: (6) JVC BR-S822U's, (3) JVC BR-7000 series, (3) JVC BR-S500U, (2) JVC BR-S800U, JVC GR-800U and (2) GR-860U Editing Controllers, Sony FXE-100 Video Switcher/Effects Generator, (5) Time Code Generator/Readers, (1) Sony SLO-1800 (Beta), (2) Alesis ADAT-XT, (1) Sony DXC-1200 TV Camera, Pioneer VP-1000 Laser Disc Player plus many consumer grade Beta and VHS VCR's. Passionate electronics enthusiast since 1973...most anything except computers. Check out my collection at www.barrys8trackrepair.com/MyVideoGear.html

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