Barry777
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Jan 16, 2010, 6:53 PM
Post #9 of 12
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Re: [RussLA] No picture on commercial tapes; home-recorded ones are fine
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No offense intended, but I would question the ability of a novice (my guess since you asked for head cleaning advice) to successfully replace video heads, especially without a few pieces of test gear, an eccentricity gauge and the service manual to perform any needed minor adjustments afterwards. Admittedly, some heads can be changed out and will work just fine, but others will require minor adjustments to the tape path and possibly even a few small tweaks in the electronic circuits to match the new heads with the rest of the unit.
It's extremely unlikely that the simple action of playing tapes would break the heads, so here is the way I've been cleaning video heads for a few decades. Keep in mind that my technique is not recommended in any service manual, but is a bit more thorough.
Poke a finger through a clean (and discardable) T shirt and dip it in alcohol. Household isopropyl alcohol works just fine - or Everclear if you're a heavy drinker! Then, VERY, VERY LIGHTLY "touch" them (the word "rub" suggests too much force) up and down 30 or 40 times. Virtually all service manuals say never to rub up and down as this could break off the fragile and narrow ferrite wafer that constitutes the physical part of the head. But the sides of the actual head are more likely to have sharp edges for the T shirt to catch on than the top and bottom of the head - thus, I always "touch" up and down rather than side to side - especially since the head gap is vertical; rubbing up and down is less likely to let material get lodged in the gap should the epoxy that covers it be worn away and the gap exposed.
Make sure you're addressing the actual heads; they look like narrow slots in the middle of the head drum, each about 3/16" wide and extremely small from top to bottom. If you can see any evidence of dirt at all on the T shirt, that means the video heads were extremely dirty (in most cases, you can restore the picture - but still not be able to see the dirt that was removed). If you can't feel the heads protruding slightly from the head drum while cleaning, then they could be very worn and possibly at the end of their expected life - but video heads generally last a good 5000 hours, so you'd have to watch tons and tons of movies to wear them out.
Proper VCR cleaning also includes the rest of the upper and lower drum, as well as the tape guides and audio/control head - but the quick operation described above will at least tell you if the problem is very dirty heads. Whatever you do, don't use anything with loose and sheddable material on the video heads, as this can cause fabric to be left on the heads and lodged in the gap which kills the picture - NO Q Tips allowed here. As far as head cleaning tapes go, they are good for one thing: if you're in the middle of a movie, lose the picture and want a quick fix to see the rest of the movie without opening the machine. Other than that, they are completely useless and only redistribute the dirt - they don't really remove anything. They can even take dirt from the erase head, back tension pawl and entrance guide and transfer it to the video heads, making them even dirtier! I never, ever use any type of cleaning tapes - when they are included in a lot of movies I purchase, they go straight in the trash, even when they are brand new and still sealed.
If you end up replacing the heads, good luck. But without a eccentricity or head protrusion gauge (used only to measure drum runout in this instance), you could end up with a head drum that wobbles a tiny bit, enough to make the picture move from side to side, jitter or cause other viewing problems. Also, if the original head assembly is not made and adjusted exactly the same as the new head, you could have trouble with the dihedral (heads not being exactly 180 degrees apart), headswitching point or a host of other minor (but aggravating) ailments. And these days, it's unlikely that you could find a local shop that is still set up for critical VCR work. This means paying shipping both ways - and the labor charges - to have it professionally adjusted somewhere. If it turns out that the SP heads are shot, you would likely be better off getting another VCR from Goodwill for 10 or 20 bucks. Most of them work just fine, needing only an idler tire and maybe a belt or two for reliability over the next several years.
Good luck!
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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 Jan 16, 2010, 7:25 PM)
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