OT: just for those intersted about analog tape

[Bill Akers]

Bill Vermillion wrote:

> On Fri, Jan 07, 2005 at 11:25 , Bill Akers gie sprachen "Vyizdur 
> zomen emororz izaziz zander isorziz", and continued with:
> 
> 
>>Bill Vermillion wrote:
> 
> 
>>>If you got the wrong sync pulse the picture would slip down 1/2
>>>frame. 
> 
> 
>>What??? Please explain what this does!!! My experience says it
>>would just lose a part of one frame and all subsequent frames
>>would be right back in proper order.
> 
> 
> I'm pulling this from memory of about 35-40 years ago.  
> 
> I'm trying to remember if I saw the guy editing the tape
> at KXLY-TV in Spokane Wash, of WFTV in Orlando.  If it was
> the former that was in 1962 and the machine was an RCA VTR-1 [or
> something close to that].   That was a CBS station and I thought it
> was strange as the local NBC station also had an RCA and I'd have
> thought with the competition they would go with Ampex.
> 
> Three 6 foot tall racks.   I left Spokane for Orlando
> in August of 1962 - so forgive me if my memory has rusted like the
> tape.
> 
> 
> It's been so long since I've been near one of those beasts you
> could be right.  I didn't do the editing but was wathching someone
> else.  That was in the days when all TV had vertical hold and
> horizontal hold knobs on the front too.

The reason for the knobs was to compensate for warming up and aging of 
vacuum tubes and other components. Over time the inter-electrode 
capitance of the vacuum tube, or the capacitive or indusctive values 
of circuit components, would change slightly to a lot causing the 
vertical or horizontal  oscillator's frequency to shift enough that it 
could no longer be synced by the sync signals that were part of the 
video stream from the station. The hold knobs were used to compensate 
properly for this phenomenon. I can understand if the station wanted 
to be precise enough to prevent the customer's television from 
'flickering' during a show, but how did they prevent it from happening 
when switching from a show to a commercial for instance?

> 
> Bill