[TechAssist] Re: Best way to clean a head.
- From: "Don Hartigan" <hartstv@xxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Mon, 26 Nov 2001 08:36:45 -0400
Tks Jeff,will get in touch with customer &try a cleaning of unit for
him..Don
----- Original Message -----
From: "Jeff Dougherty" <jeff@xxxxxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Monday, November 26, 2001 12:49 AM
Subject: [TechAssist] Re: Best way to clean a head.
>
> Don...negative..this is a good indication a head is bad...on a four head
> unit.
> One set is used for playback, the other is used for FF/REW/ search and
pause
> mode.
> A good cleaning usually fixes these..I must have missed the original one
on
> this.
>
> 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: "Don Hartigan" <hartstv@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Sunday, November 25, 2001 5:01 PM
> Subject: [TechAssist] Re: Best way to clean a head.
>
>
> >
> > I totally agree with Dennis.Normally if you ''pause'' your p/b &any
> portion
> > of the pix is clear it's a good chance your heads are ok.A customer
> recently
> > asked me about his 8mm video cam,which I no longer service,because of my
> 56
> > year old eyes ¬ too steady hand,if I though his video heads were bad
on
> > his unit.Normal p/b was very snowy,BUT,if he paused or did a forward
> > search,the pix was clear.I told him I was almost 90% sure his heads were
> not
> > the problem.Hope I did not steer him wrong....my 0.02c...Don
> > ----- Original Message -----
> > From: "Dennis Viereck" <wa6ati@xxxxxxxxxxxxxx>
> > To: <techassist@xxxxxxxxxxxxx>
> > Sent: Sunday, November 25, 2001 10:06 AM
> > Subject: [TechAssist] Re: Best way to clean a head.
> >
> >
> > >
> > > 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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