[TechAssist] Re: Best way to clean a head.
- From: "OrpheusComputing.com Repair" <techassist@xxxxxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sun, 25 Nov 2001 09:47:57 -0600
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
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Fax: 209-882-9602
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(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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