Component Video cuts out

T

TonyS

Guest
Just wondering if any one else has had this happening, or maybe a suggestion on
how to approach this problem:

I started using the component input on my Pavo 32" LCD TV.
Depending on the change in picture brightness the unit seems to lose sync and
switches to "black screen" for a few seconds.
Strong changes from black or white dominated picturs cause problems, otherwise
it works fine.
When the picture comes back it shows the input mode indicator, like it does when
I manually change the input selection.

I suspect that the Y-signal input might be AC-coupled and the picture contents
causes momentary DC level changes which confuse the sync pulse logic.

I have no schematics for the TV. I imagine increasing coupling C value could fix
the problem??

(Other input modes work fine)

Any ideas?

Thanks

Tony
 
"TonyS" <scarborofun@gmail.nspm.com> wrote in message
news:489a5bb8$0$24191$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
Just wondering if any one else has had this happening, or maybe a
suggestion on how to approach this problem:

I started using the component input on my Pavo 32" LCD TV.
Depending on the change in picture brightness the unit seems to lose sync
and switches to "black screen" for a few seconds.
Strong changes from black or white dominated picturs cause problems,
otherwise it works fine.
When the picture comes back it shows the input mode indicator, like it
does when I manually change the input selection.

I suspect that the Y-signal input might be AC-coupled and the picture
contents causes momentary DC level changes which confuse the sync pulse
logic.

I have no schematics for the TV. I imagine increasing coupling C value
could fix the problem??

(Other input modes work fine)

Any ideas?
Click to expand...
The lead (conductor) resitance might be higher on the Y-signal causing loss
of signal strength, try changing the colours of the leads around to see if
it follows the Y-Lead ie: Temporarily substitute the lead.

Thanks

Tony
Click to expand...
 
-=Spudley=- wrote:
"TonyS" <scarborofun@gmail.nspm.com> wrote in message
news:489a5bb8$0$24191$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
Just wondering if any one else has had this happening, or maybe a
suggestion on how to approach this problem:

I started using the component input on my Pavo 32" LCD TV.
Depending on the change in picture brightness the unit seems to lose sync
and switches to "black screen" for a few seconds.
Strong changes from black or white dominated picturs cause problems,
otherwise it works fine.
When the picture comes back it shows the input mode indicator, like it
does when I manually change the input selection.

I suspect that the Y-signal input might be AC-coupled and the picture
contents causes momentary DC level changes which confuse the sync pulse
logic.

I have no schematics for the TV. I imagine increasing coupling C value
could fix the problem??

(Other input modes work fine)

Any ideas?


The lead (conductor) resitance might be higher on the Y-signal causing loss
of signal strength, try changing the colours of the leads around to see if
it follows the Y-Lead ie: Temporarily substitute the lead.
Click to expand...
I already tried changing signal levels via resistors, cause I suspected a
latch-up effect. Smaller signals reduce the number of cut-outs but also the
contrast of course...


Thanks

Tony
Click to expand...
 
TonyS wrote:
-=Spudley=- wrote:
"TonyS" <scarborofun@gmail.nspm.com> wrote in message
news:489a5bb8$0$24191$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
Just wondering if any one else has had this happening, or maybe a
suggestion on how to approach this problem:

I started using the component input on my Pavo 32" LCD TV.
Depending on the change in picture brightness the unit seems to lose
sync and switches to "black screen" for a few seconds.
Strong changes from black or white dominated picturs cause problems,
otherwise it works fine.
When the picture comes back it shows the input mode indicator, like
it does when I manually change the input selection.

I suspect that the Y-signal input might be AC-coupled and the picture
contents causes momentary DC level changes which confuse the sync
pulse logic.

I have no schematics for the TV. I imagine increasing coupling C
value could fix the problem??

(Other input modes work fine)

Any ideas?


The lead (conductor) resitance might be higher on the Y-signal causing
loss of signal strength, try changing the colours of the leads around
to see if it follows the Y-Lead ie: Temporarily substitute the lead.


I already tried changing signal levels via resistors, cause I suspected
a latch-up effect. Smaller signals reduce the number of cut-outs but
also the contrast of course...


Thanks

Tony
Click to expand...
To honour the big interest in this post I have a follow up:)

I bit the bullet and opened up the guts of the Flatty, and I found:

1. The input selector FET Mux switch (ADG794) can't, according data sheet, even
handle any negative voltage. (abs max -0.3V). Hence the AC coupled 1Vpp Y-signal
will hardly come out OK at the output. Sync pulses are negative....

2. The Signal Processor chip TVP8160 is actually designed to clamp input
signals. If only there was no mux chip first ....
And it is actually designed to handle 576p signals max.

So what does it mean, "HDTV ready" as stated in the TV specs (Pavo PLD-3200)?
Not sure what happens to my 1080i signal.

Anyway, be careful buying stuff on ebay.

Tony
 
Runs the other way now when seeing the name "Pavo".
Thanks.

"TonyS" <scarborofun@gmail.nspm.com> wrote in message
news:489bce2c$0$24173$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
TonyS wrote:
-=Spudley=- wrote:
"TonyS" <scarborofun@gmail.nspm.com> wrote in message
news:489a5bb8$0$24191$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
Just wondering if any one else has had this happening, or maybe a
suggestion on how to approach this problem:

I started using the component input on my Pavo 32" LCD TV.
Depending on the change in picture brightness the unit seems to lose
sync and switches to "black screen" for a few seconds.
Strong changes from black or white dominated picturs cause problems,
otherwise it works fine.
When the picture comes back it shows the input mode indicator, like it
does when I manually change the input selection.

I suspect that the Y-signal input might be AC-coupled and the picture
contents causes momentary DC level changes which confuse the sync pulse
logic.

I have no schematics for the TV. I imagine increasing coupling C value
could fix the problem??

(Other input modes work fine)

Any ideas?


The lead (conductor) resitance might be higher on the Y-signal causing
loss of signal strength, try changing the colours of the leads around to
see if it follows the Y-Lead ie: Temporarily substitute the lead.


I already tried changing signal levels via resistors, cause I suspected a
latch-up effect. Smaller signals reduce the number of cut-outs but also
the contrast of course...


Thanks

Tony



To honour the big interest in this post I have a follow up:)

I bit the bullet and opened up the guts of the Flatty, and I found:

1. The input selector FET Mux switch (ADG794) can't, according data sheet,
even handle any negative voltage. (abs max -0.3V). Hence the AC coupled
1Vpp Y-signal will hardly come out OK at the output. Sync pulses are
negative....

2. The Signal Processor chip TVP8160 is actually designed to clamp input
signals. If only there was no mux chip first ....
And it is actually designed to handle 576p signals max.

So what does it mean, "HDTV ready" as stated in the TV specs (Pavo
PLD-3200)? Not sure what happens to my 1080i signal.

Anyway, be careful buying stuff on ebay.

Tony
Click to expand...
 
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