Barry777
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Jun 2, 2010, 4:47 AM
Post #9 of 26
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Re: [heviarti] Toploader Magnavox issues
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Ahhh, so the tape does start moving for - let me guess - about 3 seconds? Your rotation sensor is probably dirty. You'll need to remove the takeup reel and clean the mirror-like pattern on the bottom of it. The broken-mirror pattern reflects light onto a phototransistor underneath, generating a regular pulse which tells the computer that the reel is turning. When the mirror gets dirty, it won't reflect enough light to generate the necessary pulses and the VCR shuts down to prevent damage to the tape. Of course, if the capstan keeps pulling the tape through and the takeup reel is not taking it up, mucho tape will spill into the machine.
On some models, the rotation sensor is driven by a small belt (again, from the takeup reel) and is a rotating magnet which affects something called a Hall Effect sensor. Same job, different junk to perform it. Hall sensors do go bad, but not very often. But the majority of those old heavy machines used the mirror on the bottom of the takeup reel, and you'll see the phototransistor underneath - might as well clean that too. Whichever arrangement is used, the machine is not sensing the rotation of the takeup reel. That's probably the second or third most common trouble with older VCR's.
If cleaning the mirror doesn't do it, then either the phototranstor has failed (unlikely) or the connections from the phototransistor to the processor need to be checked. The processor itself should be fine, but there are multitudes of connectors on those old VCR's, and plenty of opportunity for oxidized connectors to start making poor contact. But cleaning the mirror fixes this problem about 90% of the time.
Another good thing to do on any old VCR is to "exercise" all the connectors - pull them out, spray a little WD-40 on them, then insert them back into their receptacles and remove them again several times - this cleans the connections and restores reliable contact. The best tool to remove these connectors is a pair of needle nose pliers, with a tiny notch filed into the jaws right at the ends. This customized tool enables you to grab those connectors so you don't pull on the wires themselves. Not a good idea to pull on the wires, as these connectors will often be "glued" into their sockets with either a combination of dust and grime, or in some cases they like to coat them with Humiseal to protect them from moisture and keep them from coming out from vibration, shipping, etc.
Anyway - I'm almost certain it's the little mirror on the bottom of the takeup reel. Get to work - what are we not paying you for? ;-)
P.S. - VCR's that old used a wired remote. There should be a 1/8 inch phone jack somewhere on the front for this. Not familiar with the model, but that was the general arrangement back then.
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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
(This post was edited by Barry777 on Jun 2, 2010, 4:50 AM)
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