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Vector/Waveform Tek 1740A showing a ball instead of vector

Alexandre Souza
 

Greetings all!

Just got a Tek 1740A vectorscope. After some basic maintenance everything is working BUT the vector part.

Instead of the vectors, it shows a "rotating ball" in the screeen. It is just like if it were showing the vectorscope screen, but rotating around its axis

Video of the problem at https://www.youtube.com/watch?v=Lk-yPvYRAAE

I could use some help where to start...I have the service manual

Thanks!
Alexandre Souza

(Yes, I'm back =) )
--
---8<---Corte Aqui---8<---
https://www.tabalabs.com.br
https://tabajara-labs.blogspot.com

Harvey White
 

looks like no lock between the internal 3.58 and the signal 3.58, so the burst never can stay still.

Harvey

On 9/12/2019 2:06 PM, Alexandre Souza wrote:
Greetings all!

Just got a Tek 1740A vectorscope. After some basic maintenance everything is working BUT the vector part.

Instead of the vectors, it shows a "rotating ball" in the screeen. It is just like if it were showing the vectorscope screen, but rotating around its axis

Video of the problem at https://www.youtube.com/watch?v=Lk-yPvYRAAE

I could use some help where to start...I have the service manual

Thanks!
Alexandre Souza

(Yes, I'm back =) )

Alexandre Souza
 

Thanks a lot, Harvey! Spot On!

I confess I don't know much about vectorscopes, and got this one as a tool
to help me with some videogame / old computer video mods. And one of the
misunderstandings was created by my color bar generator (I should have
bought a tektronix...). I connected my VERY OLD color bar generator to the
1740 and this was the result. Later, just for the sake of curiosity, I
connected my Apple IIe to the 1740 and it locked perfectly WHEN IN GRAPHICS
MODE since there is no subcarrier in text mode (color killer activated)

Now I know - You GOTTA HAVE a correct subcarrier on the signal for the
vectorscope to lock on

Always learning new tricks =) Thanks you all!

---8<---Corte aqui---8<---
http://www.tabajara-labs.blogspot.com
http://www.tabalabs.com.br
---8<---Corte aqui---8<---


Em qui, 12 de set de 2019 às 22:07, Harvey White <madyn@...>
escreveu:

looks like no lock between the internal 3.58 and the signal 3.58, so the
burst never can stay still.

Harvey


On 9/12/2019 2:06 PM, Alexandre Souza wrote:
Greetings all!

Just got a Tek 1740A vectorscope. After some basic maintenance
everything is working BUT the vector part.

Instead of the vectors, it shows a "rotating ball" in the screeen. It
is just like if it were showing the vectorscope screen, but rotating
around its axis

Video of the problem at https://www.youtube.com/watch?v=Lk-yPvYRAAE

I could use some help where to start...I have the service manual

Thanks!
Alexandre Souza

(Yes, I'm back =) )


Harvey White
 

From the center out, the distance (not the direction) is proportional to the magnitude of the subcarrier.  The angle of the vector/dot is the phase difference from the color burst.  The little boxes show you where the appropriate values ought to be. What I think it wants to see is the color burst, and it can sync to that, since *everything* is relative to the burst phase, frequency, and amplitude.

It's a neat way to see what colors are doing in the old NTSC system.

Harvey

On 9/12/2019 11:26 PM, Alexandre Souza wrote:
Thanks a lot, Harvey! Spot On!

I confess I don't know much about vectorscopes, and got this one as a tool
to help me with some videogame / old computer video mods. And one of the
misunderstandings was created by my color bar generator (I should have
bought a tektronix...). I connected my VERY OLD color bar generator to the
1740 and this was the result. Later, just for the sake of curiosity, I
connected my Apple IIe to the 1740 and it locked perfectly WHEN IN GRAPHICS
MODE since there is no subcarrier in text mode (color killer activated)

Now I know - You GOTTA HAVE a correct subcarrier on the signal for the
vectorscope to lock on

Always learning new tricks =) Thanks you all!

---8<---Corte aqui---8<---
http://www.tabajara-labs.blogspot.com
http://www.tabalabs.com.br
---8<---Corte aqui---8<---


Em qui, 12 de set de 2019 às 22:07, Harvey White <madyn@...>
escreveu:

looks like no lock between the internal 3.58 and the signal 3.58, so the
burst never can stay still.

Harvey


On 9/12/2019 2:06 PM, Alexandre Souza wrote:
Greetings all!

Just got a Tek 1740A vectorscope. After some basic maintenance
everything is working BUT the vector part.

Instead of the vectors, it shows a "rotating ball" in the screeen. It
is just like if it were showing the vectorscope screen, but rotating
around its axis

Video of the problem at https://www.youtube.com/watch?v=Lk-yPvYRAAE

I could use some help where to start...I have the service manual

Thanks!
Alexandre Souza

(Yes, I'm back =) )


Michael A. Terrell
 

TV shop grade colorbar generators used non standard frequencies to create
their bars. I once used a Heathkit IG28 at a TV station to transmit a color
station ID over color bars at a monochrome station. It drove the master
sync generator nuts, to genlock to the alien signals.

On Thu, Sep 12, 2019 at 11:27 PM Alexandre Souza <
alexandre.tabajara@...> wrote:

Thanks a lot, Harvey! Spot On!

I confess I don't know much about vectorscopes, and got this one as a tool
to help me with some videogame / old computer video mods. And one of the
misunderstandings was created by my color bar generator (I should have
bought a tektronix...). I connected my VERY OLD color bar generator to the
1740 and this was the result. Later, just for the sake of curiosity, I
connected my Apple IIe to the 1740 and it locked perfectly WHEN IN GRAPHICS
MODE since there is no subcarrier in text mode (color killer activated)

Now I know - You GOTTA HAVE a correct subcarrier on the signal for the
vectorscope to lock on

Always learning new tricks =) Thanks you all!

---8<---Corte aqui---8<---
http://www.tabajara-labs.blogspot.com
http://www.tabalabs.com.br
---8<---Corte aqui---8<---


Em qui, 12 de set de 2019 às 22:07, Harvey White <madyn@...>
escreveu:

looks like no lock between the internal 3.58 and the signal 3.58, so the
burst never can stay still.

Harvey


On 9/12/2019 2:06 PM, Alexandre Souza wrote:
Greetings all!

Just got a Tek 1740A vectorscope. After some basic maintenance
everything is working BUT the vector part.

Instead of the vectors, it shows a "rotating ball" in the screeen. It
is just like if it were showing the vectorscope screen, but rotating
around its axis

Video of the problem at https://www.youtube.com/watch?v=Lk-yPvYRAAE

I could use some help where to start...I have the service manual

Thanks!
Alexandre Souza

(Yes, I'm back =) )