opppssss T160 tape...not a T120... MONTE MONCRIEF BAKERSFIELD, CA. DOCVIDEO@xxxxxxxxxx ----- Original Message ----- From: "DOCVIDEO" <DOCVIDEO@xxxxxxxxxx> To: <techassist@xxxxxxxxxxxxx> Sent: Sunday, November 25, 2001 6:50 PM Subject: [TechAssist] Re: HOW MANY MILES DOES VIDEO HEAD TRAVEL??? Should be little over 142.4 miles on a T120 tape... Drum is roughly 8 inches around , turns 39.17 times per second based at 2350 RPM in EP mode = 313.3 inches [per second] = 480 minutes= 28,800 seconds X 313.3 inches = 9,024,000 inches. 1 mile = 5280 feet= 63,360 inches 63,360 inches into 9,024,000 = 142.4+ miles Based on a JVC VCR which moves 11.12 mm per second of tape X 480 minutes [ 28,800 seconds] .....[ length time takes to record a full tape] = .4377944 inches per second X 28,800 seconds = 12,608.47872 inches of tape moved/recorded on. MONTE MONCRIEF BAKERSFIELD, CA. DOCVIDEO@xxxxxxxxxx ----- Original Message ----- From: "OrpheusComputing.com Repair" <techassist@xxxxxxxxxxxxxxxxxxxx> To: <techassist@xxxxxxxxxxxxx> Sent: Sunday, November 25, 2001 7:47 AM Subject: [TechAssist] Re: Best way to clean a head. For the TAPE, the "actual writing speed" if I remember correctly is 19 fps. 3600 seconds in an hour, so 6 hrs has 21,600 sec in it. Traveling at 19 fps, that's 410,400' or roughly 78 mi. that is "writes". Not sure if that's what you mean by "travels". :-) -Clint Happy Thanksgiving & God Bless Us All Clint Hamilton, Owner http://OrpheusComputing.com http://ComputerHardware-ConsumerElectronics.com sales@xxxxxxxxxxxxxxxxxxxx Fax: 209-882-9602 TechAssist Administration http://tech-assist.org techassist@xxxxxxxxxxxxx 4orpheus@xxxxxxxxxxxxx (alternates) orpheuscomputing@xxxxxxxxx (PLEASE include our previous correspondence if replying to this email!!) > Larry: > > I disagree with your statement, "I takes 2 heads to complete a full picture". > If on head is bad and the other good you will be missing 1 field of video. If > you remember oUR NTSC format consists of 1 frame of video is equivalent to two > fields. The fields are interleaved together not appended to to the end of the > first field. > Since they are interleaved together one will end up with 1 line of video and 1 > line of snow then 1 line of video and 1 line of snow. This pattern will > continue > throughout the entire video field. > > The reason you get a picture on half of the screen, usually the top, is > because > of head protrusion. The surface of the head must impinge into the tape > slightly > just after the entrance guide. This impingement depth must continue for the > entire 180 degree swipe of the video head "A" and repeat this process for > video > head "B". > The main factor that effects head protrusion are wear. Obviously head wear is > something that only replacement is the answer. Insufficient back tension > coupled > with head wear is usually responsible for the assessment mentioned, "even and > inch of video showing on the screen the heads are good" I would agree with in > part. > > As the video head travels around at 1800 rpm it creates air turbulence, This > turbulence does not negatively effect the entrance side of the drum assembly > where the tape meet the head. In fact the trailing side of the video head chip > had a lower pressure and will suck the tape in closer to the head. But after > the > head has traveled 60+ millimeters to playback or record of the first video > field > it looses the head to tape contact. One or two primary factors can cause this, > insufficient back tension and head wear. > > Any debris on the drum, or the video, or HI-FI heads can cause the tape to be > pushed away from the head trying to read it. This is why the air channels in > the > drum must be kept free of any debris too. It is just as important as the video > head chips. > > > I have a brainteaser for the group. How many miles does single video head > travel > in 1 single pass of a 6 hour EP VHS tape? > > Dennis Viereck > > > > > > > > > Ledstiles@xxxxxxx wrote: > >> In a message dated 11/24/2001 4:27:32 PM Pacific Standard Time, >> billmcfarland@xxxxxxxxxxxxxx writes: >> >> << >>>>> Howdy Wally, >>>>> If the heads are bad there won't be any video showing on the screen, >> if >>>> you have even and inch of video showing on the screen the heads are >> good, >>>> >> Wally . This above is sooooo wrong. Most bad head problems I run across have >> the 1/2 good picture display. I takes 2 heads to complete a full picture >> after all. >> Larry >> N.C.S. ================================= Help make your TechAssist database better! 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