[TechAssist] Re: Best way to clean a head.
- From: "OrpheusComputing.com Repair" <techassist@xxxxxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sun, 25 Nov 2001 13:05:31 -0600
Well, there's still the same amount of tape used, T-120 6 hr
tape is ~246m :-) FYI, actual tape speed is .4375 in/sec. @
EP, but the 'writing speed' is different because (like you
said) of the helical angle ratio of the tape VS the drum.
Something else that may be of interest to any 'newbies' out
there....the hi-fi audio quality is actually better in most
cases @ EP (slowest speed) because due to the rotation of the
head drum, it is the same direction of the tape path; so if
you slow that down to EP, the tape of course then is going
slower therefore the 'writing speed' is increased. It is
usually not noticeable to ears since the audio specs are so
good to begin with, but it does show on paper. Usually about
1khz lower on the high end, but since you are dealing with
around 19-21khz, that's not usually noticeable unless you are
below 20 yrs old, have great high frequency hearing, and are
recording something with content in that audio range. (I
know Jeff knows all this but a few others may not).
-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
----- Original Message -----
From: "Jeff Dougherty" <jeff@xxxxxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Sunday, November 25, 2001 11:50 AM
Subject: [TechAssist] Re: Best way to clean a head.
This may be how much tape is used. The helical position that
the tape sits
allows less tape to be used then if it were pulled straight
across the
heads.
Jeff
mailto:Jeff@xxxxxxxxxxxxxxxxxx www.9-11-2001tragedy.com
FAX 1-413-280-0677
Intrepid Video & Electronics
Harrisburg, PA 17111
717-909-8844
www.intrepid-video.com www.tech-repair.net
www.thetoolcaddy.com
----- Original Message -----
From: "OrpheusComputing.com Repair"
<techassist@xxxxxxxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Sunday, November 25, 2001 10:47 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.
>
>
>
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