vertical lines in a Toshiba TV

[old_tv_nut]

Yes, it's possible this is a design flaw with this chassis, but it's so clearly visible in your photo, I wonder. I presume the bars don't move wildly, just get stronger or weaker when you change brightness?

You might try running added ground wires between boards, not following the path of the original ones, to see if it changes. (Still grasping at straws here.)

[Alex KL-1]

Another thing very unlikely for a SS set, but anyway: the image are compressing at the bands positions? Tube sets sometimes makes that. Just seeing another thread. But, by design, SS systems are less prone to that.

OOPS, nevermind... it varies with bright, cannot be this cause.

[vol.2]

Originally Posted by old_tv_nut

Yes, it's possible this is a design flaw with this chassis, but it's so clearly visible in your photo, I wonder. I presume the bars don't move wildly, just get stronger or weaker when you change brightness?

No, the bars don't move at all. They are completely static. Depending on the brightness, they can appear to be either lighter lines on a darker background or darker lines on a brighter background, but I believe that's normal and is just an illusion; as the brightness value gets higher, the lines seem to disappear because (I assume) the voltage level on the raster overtakes the resolution of the lines (causes it to bloom over the bars)

You might try running added ground wires between boards, not following the path of the original ones, to see if it changes. (Still grasping at straws here.)

I could try that. I have to admit it seems like a long shot, but why not.

Originally Posted by Alex KL-1

Another thing very unlikely for a SS set, but anyway: the image are compressing at the bands positions? Tube sets sometimes makes that. Just seeing another thread. But, by design, SS systems are less prone to that.

OOPS, nevermind... it varies with bright, cannot be this cause.

Yeah, also, it definitely doesn't warp a video image at all. I see no compression.

In fact, if a busy image is on the screen, I can't see the bars at all. It's only noticeable in areas of solid color or grey.

[old_tv_nut]

"as the brightness value gets higher, the lines seem to disappear because (I assume) the voltage level on the raster overtakes the resolution of the lines (causes it to bloom over the bars)"

Now I wonder if we're looking at the same thing. I have been assuming you have been talking about the fairly narrow dark and bright vertical bars that extend at least a fifth of a way into the picture from the left. These are far too wide for spot blooming to average out unless you are seeing the picture go terribly out of focus at high brightness. They could, however, be a power bus or ground transient coming from the power supply that reduces in amplitude as the power supply is loaded more heavily.

[vol.2]

Originally Posted by old_tv_nut

Now I wonder if we're looking at the same thing.

I see the same thing you are seeing.

I have been assuming you have been talking about the fairly narrow dark and bright vertical bars that extend at least a fifth of a way into the picture from the left.

They do, but then you can see there are also some narrower lines on the right side of the screen. There is one lighter thin bar towards the right. It seems like they are wide on the left, and get narrow towards the right until they are very thin. I would assume the lines are wider on the left because the energy from the flyback is greatest just after the refresh period.

These are far too wide for spot blooming to average out unless you are seeing the picture go terribly out of focus at high brightness.

That was just a guess. I was describing what happens when I start from a blank screen and slowly turn up the brightness until I see a white raster.
It made sense to me that the raster itself was what is blooming as a whole solid screen of white, not the spots surrounding the bars.

They could, however, be a power bus or ground transient coming from the power supply that reduces in amplitude as the power supply is loaded more heavily.

How do think I could solve that if it was true?

Thanks

[Alex KL-1]

To be fair, sometimes I seen (and have) some sets with some artifact. I have one Toshiba with horrible black clamping and inomogeneous near black screen. But is not much the near black artifact, and is easy to dismiss it, unless someone are playing a proper bright/cutoff adjusted Resident Evil game (even the ones from Playstation 1)... but I not dismiss it's black level unstability (very sensitive to contrast; it can be a strong CRT currrent limiting or suchlike). I did NOT solve it, since I'm using it now only for the Atari (then is indirectly solved due to usage ;-)

[Username1]

.

Hi - The lines on the screen line up perfectly to point to a horizontal drive pulse, or
possibly a harmonic, or ringing etc. I don't think it's injected anywhere, but it may
be on the power supply lines, any of them. Do you have a scope? You may need
one to find this. I would look at each of the voltage sources for this 1/15734
or multiple showing up on voltage source lines. All these sources are also
providing bias for the picture tube, & it's drivers, so if it's in the power
supply, you can bet it's in the tube when no picture is present to begin
with, and it's still there with picture information. So set your scope
to capture several H pulses possible set sync to the H pulse,
and look for itsy bitsy H frequency ripple in the power supply.

You see your power supply has lots of choke's in it along with
caps to filter out flyback noise at each source point.

I doubt this came from the factory like that, the Japanese
are very meticulous about how their stuff operates....

.

[old_tv_nut]

Originally Posted by vol.2

How do think I could solve that if it was true?

Thanks

As Alex says, a scope might help. Are you sure the frequency is changing from left to right? I can't think of something that would do that.

[old_tv_nut]

Wild thought - try connecting something like a 0.1 microfarad 400 volt capacitor from green output collector to ground and see if it attenuates it. That woud tell you if it's coming through the video circuits somehow.

[zeno]

Design flaw ? NO WAY !
If you got a scope. Set to display a BLANK, not even snow pix.
Be sure the G-2 is set proper. Color level at zero.
Look at the @200V should be clean. Same with the 3 video outs.
There almost HAS to be crap on them.
Check the E of the 3 outs for garbage also. Trace back.
There is a little PS that runs the EXT for isolation, Check that.
There is an "IF mute". didnt trace but probably turns off IF's when
on ext..
Dont forget the blanking stage also for a look-see.

Zeno

[vol.2]

Yes, I have a scope. I have already scoped the power supplies and the video. Didn't see anything fishy.

Originally Posted by Username1

.
Hi - The lines on the screen line up perfectly to point to a horizontal drive pulse, or
possibly a harmonic, or ringing etc. I don't think it's injected anywhere, but it may
be on the power supply lines, any of them. Do you have a scope? You may need
one to find this.

Yes, I had come to this conclusion already. That's why I said the pulse is strongest right after the horizontal refresh.

I would look at each of the voltage source for this 1/15734
or multiple showing up on voltage source lines. All these sources are also
providing bias for the picture tube, & it's drivers, so if it's in the power
supply, you can bet it's in the tube when no picture is present to begin
with, and it's still there with picture information. So set your scope
to capture several H pulses possible set sync to the H pulse,
and look for itsy bitsy H frequency ripple in the power supply.

They were all clean when I checked. I can see the flyback pulses, but nothing that looks like it would be happening during scan time.

Originally Posted by zeno

Design flaw ? NO WAY !
If you got a scope. Set to display a BLANK, not even snow pix.
Be sure the G-2 is set proper. Color level at zero.
Look at the @200V should be clean.

It's 178V. I can see the flyback pulses in it, but they are outside of scan time. Nothing like the ripple or otherwise bars I see on the screen.

Same with the 3 video outs.
There almost HAS to be crap on them.

Don't see anything.

Check the E of the 3 outs for garbage also. Trace back.

The emitter? Not sure if I did that.

There is a little PS that runs the EXT for isolation, Check that.

Are you talking about the optical input chip's isolated ground?

There is an "IF mute". didnt trace but probably turns off IF's when
on ext..
Dont forget the blanking stage also for a look-see.

That's a little bit above my head. I would need more explanation to grock it.

[Username1]

.

During post Vol 2 above you said -

They were all clean when I checked. I can see the flyback pulses, but nothing that looks like it would be happening during scan time.


Quote:

It's 178V. I can see the flyback pulses in it, but they are outside of scan time.

Nothing like the ripple or otherwise bars I see on the screen.

end Quote.

If there is a H pulse on it, then that's what is on the screen. That's why you have to
look up-freq. from the H-Pulse, Look for a harmonic as there are several light &
dark lines on the screen. If there is a harmonic it may occur during scan time.

Anyway if you see stuff on the 200V line, how are you sure it's not happening
during scan time? Anyway if it's happening on both sides of the screen then
it's also happening during the damper scan too. To me that points to H-Pulse
or harmonics on Power Supply lines.....

If there is for example 10 defined lines on the screen, then it's possible that
there is a noise source 10X 15, 734 on the screen....

.

[vol.2]

Originally Posted by Username1

Anyway if you see stuff on the 200V line, how are you sure it's not happening
during scan time?

Because the pulses are spaced properly and the waveform matches the service manual perfectly.

Anyway if it's happening on both sides of the screen then
it's also happening during the damper scan too. To me that points to H-Pulse
or harmonics on Power Supply lines.....

I think it's obviously the H-Pulse ringing that's getting through somehow, but I don't see it on the power supply lines because they all the waveforms look "correct" as per the manual, and they make sense in that the pulses from the flyback are spaced properly. The electrolytics for the power supply filter caps have all been replaced with new, high quality Nichicon caps

[Username1]

.

Happy Sunday Morning! Have you by chance scoped out the posted wave forms on
the other side of the flyback, Q402 & Q404, H-Drivers for proper size & Shape
with no out of the ordinary spikes in rising of falling sides of their pulses...?

.

[zeno]

A few things just in case.
Sams wave forms show 2 complete lines or frames.
The little isolation PS runs off the FBT. Check its filter cap.
Watch the lead dress, if to close to FBT it can cause this.
Remember cathodes high = dark pix, low =bright pix.
Scope should show a damped ring , refreshed (ping) at start of every hoz line.
That should show up on scope. Like I said it almost has to be there !
Also remember there are 2 or 3 grounds in this set.
AND since you re-capped check the polarity & value of every cap ! This is why
in most cases repair first then change a few caps & retest & so on.....

Zeno