I haven't had time to check out all of this yet, but I have a couple of responses.

I did replaced R413. I believe it was carbon film and I replaced it for like, but the Service Manual does not call out what that specific resistor is made from and I did it a long time ago. I made the best guess I could based on what came out of it.

I replaced it because that whole area of the board overheated and got a bit burnt. A lot of the resistors in that area had to be replaced.

I think it's probably worth me looking at them all again to make sure I didn't violate any of the resistor types in the manual, but I don't think I did.

Just out of curiosity, why would it matter?

I double checked the waveform coming out of Pin 64, which goes to the base of Q402 and the "overshoot" doesn't line up with scan time. I took a reading from the heater and the guns, and the overshoot on Pin 64 takes place entirely during the blanking interval. Unless there are some harmonics somewhere else, but I don't see them anwhere (yet).

Also, the base of Q402 looks clean. It's the Pin out of the video IC that has the overshoot. Once it gets connected to the 134V source, it seems to restore the waveform.

Right now, I'm thinking that there is an issue originating from the secondary windings of the flyback. There might be some issue that isn't being damped properly

I'll look into the resistors

If that hoz drive is the source it must be coming from somewhere &
getting passed along. Its a classic ring that refreshes every line.
A few things....
If you cut open a jungle IC you see its a PKG of many IC's. Each usually
has its own GND & VCC pins.
I would also look at the blanking circuit. I have seen resistors in Sharp
& others cause this. Go up in value.
Mr squirrel give good advice, If you give him some peanuts & sunflower
i am sure he will help you further !
When I get ambition I will pull the Sams so I can see everything at once

73 Zeno :beer:
LFOD !

Thanks for the advice Zeno.

Are you saying I should look at the supply voltage to those chips, or suspect the ICs?

Just for reference, I have already tried replacing the jungle IC and the main video processor IC and neither had any effect whatsoever. I have extras of both.

I replaced the resistors in the area of the board that got burned. That entails R227, R497, R413, R414. There are several other resistors in that area, but they all checked out in value. I only replaced the stuff that was off, and they were all low by significantly more than 20%, I think there's a design flaw in the circuit probably for that area to get so hot.

R416 also got replaced as it was quite off, but it's not in the immediate area that looked burned.

Not totally sure which those would be. I guess maybe I didn't mess with the blanking circuit?

Just remembered. Toshiba & others used glue on bottom of the PCB
to hold wires & parts. It gets old & crusty & eats etch & gets conductive.
Clean any out you find on anything.

Zeno:smoke:

Thanks, the bottom is very clean though. I went over the board very carefully when I recapped stuff. It has also been completely cleaned with IPA and all of the solder has been reflowed.

I'd pull my Toshiba Service Manual and "Fix Sheets" published by Toshiba, but nowhere in this thread (or title) is the model number.

So lemme ask, what's the model number?

https://videokarma.org/showthread.php?t=265964

It's the CX1467!

If you have the real Service manual that would certainly be a boon, I've only been able to locate the Sams on this one.

I notice on the 12v supply there is an L061
Which may be there or not by the schematic
Wonder if it was a mod maybe for this issue.

Interesting. I am not at home right now, but I can check in a couple days to see if those parts are there.

I question if they would have an effect though because those parts are not on the 12V(B) supply that powers the AN5352 jungle IC, they are across the (C) and (D) 12V source. The (C) source does power the output of the optocoupler ICs on the video input, but I experimented by injecting an RGB signal directly to the Jungle IC and blanking the video input signal entirely and the ringing was still present. If anything, the ringing was more visible when using an RGB signal into the jungle IC than it was before, although that might have more to do with the jungle IC and the way it handles the brightness and contrast for the OSD signal than anything else; I can get the ringing pattern to show up more sharply by messing around with the brightness and contrast on the set.

Sorry, no Manual, and fix sheets mention VITS issues (horizontal lines at very top of pix, as well as a host of audio issues. As to similar models, they all mention the warping of the shadow mask and vertical bars in the picture.....but not your model, and no specifics as to what lines are there.

From experience, filter caps in the scan-derived supplies (those off the flyback secondary) generally cause such issues (discussed ad nauseam in this thread!) AND failure to replace the ferrite beads when replacing the HOT or Horizontal Driver transistors. I remember some JVC chassis where the ferrite portion of the horizontal driver transformer cracked and caused problems with Barkhausen-like lines as well.

Sorry I fell short - Dad retired in 2008, and stopped all but his Sams and Thomson subscriptions in 2003/2004.

Thanks for looking into it. I haven't found the SM anywhere, not even on ebay.

As far as I remember, there were no ferrite beads on any of those parts; I absolutely would have noted anything like that and written it down. I am exhaustively careful when I do any work. I make a spreadsheet and write down what every part is and make notes and take pictures of everything before I do any work.

I've got another identical set in storage I can open up and check for anything different, but I probably won't get it out for awhile.

And yes, we all talked a lot about capacitors. I did replace all of those. I replaced pretty much everything at this point, certainly anything in the deflection, power supply or video.

I replaced the capacitor on the base of Q402 (0.0022uf) with a 0.003uf cap and it flattened the overshoot (so now the waveform lookin right).

Unfortunately, it made absolutely no difference to the lines on the raster. They remain ever unchanged.

Also worth noting is that the output of the H transistor Q404 looks nice an tidy.

https://i.imgur.com/rE9Sssa.jpg

With such a clean wave, the only place that Q402 could make a difference is polluting the 135V I think, which seems okay. It's got a tiny bit of noise , but it looks reasonable.

https://i.imgur.com/1OERkJn.jpg

Maybe the weirdest thing I found is that the 178V looks really noisy on the other side of L521. Not sure if this is expected, but it's on the neck board between the inductor and the three resistors which feed the output transistors.

Here's the spot in the schematic. The sam's has the inductor on the main board schematic, but it's actually on the neck board. It leaves the PCB at point 39.

https://i.imgur.com/kmu08OC.png

https://i.imgur.com/G1Zm6vH.png


On the left side of L521, it looks fine, but on the other side of L521 it has this 40Vpkpk 60Hz waveform. I guess it's the raster. It's probably normal, but I haven't looked at that many different cathode voltages in my life.

https://i.imgur.com/8sqHTuI.jpg

I've found something that I think might be significant. I can effect the vertical lines by changing the Sharpness knob on the TV. This suggests to me that it's in the video information if I can do that perhaps. This is what the lines look like when the Sharp is turned all the way up.

https://i.imgur.com/zJX1BcN.jpg

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Hi!

I guess I picked a good day to see if anything was going on at vk. So for the sharpness
knob causing the lines to be more visible or defined, - I have always thought of the
sharpness as a kind of "tone" control for the picture. You know turning up the tone
and giving the speaker more treble. So you are letting a little more treble get to
the picture tube.... It also confirms what we already know, it's higher frequency
noise, as turning up the treble also makes hiss-noise more noticeable on a speaker.

An Observation - At the edges of the screen on both the right & left it seems
that where the scan lines end it looks a bit brighter - Is it just the picture
artifact, or is it real?

In your scope picture it looks like your scan is 60hz, frame rate, If you set it
to sync to horiz sync and scoped the video amp or any of the color drivers
you are looking at, I think you would see the vert lines in each line scan.
Can you count the ripple on what should be a flat line?

I think if you did that you would find that the interference is a high
harmonic of the horiz output, again we know it.

You may want to find similar bright or dark lines on the tv screen across the entire
face of the screen, count them up, and multiply times 15,734 to see what the
frequency might be, and then use some math and see what inductor & cap.
pair makes a filter close to that frequency and those components may
be the trouble spot..... You know that tv has a LOT of coils in it.

And that voltage source that you have growing on the neck board is another
possible noise injection point. There is probably a focus voltage showing
up on that board to do it's business, and is it possible it's drooling a
few stray electrons around....?

You may also want to do a little unorthodox troubleshooting for this problem....
Take a 1/2" size nut (steel not a squirrel kind of nut) mount it tightly on a
wooden dowel and carefully move it around near all the goodies that can
be a problem area, like the coils, horiz. everything, output, flyback, etc.
Keep a good eye on the tv screen while doing it..... You know that
white screen above with the sharpness turned up. You never know
you may find a spot that changes something.... You might also
try a small magnet on a stick...... (Weak magnet)

This might need to be a 2 person experiment, you know be safe.
You can also do something similar be using a shield around some
components. And even use a 2" wire on a stick touch some
components and give them a little bit of an antenna and
let that item transmit their signal, or noise a little "more"
and see what happens....



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Hello! Happy Thursday morning!




The "bright" part is not real, but there is a real dark line in that spot on the edges of the screen on both sides. The Sharpness is creating the light artifact on the edge of those dark lines.


Not really. I tried to do that, but it looks like the ripple left over from the flyback derived power supply occurs out of frame, and I don't particularly see a distinct waveform that reflects the lines I see on the raster. If I display a dark grey (that shows the lines on the raster) and look at the cathodes (any of the three), the scope looks pretty flat (during scan time) with just some random noise. If it's in the video signal, it's very subtle because I can't see it on a scope. It may be that it's masked by my probe. Not sure.

That's why I initially thought this was not in the video. Am I correct in thinking that it has to be in the video signal if I can effect it with the Sharpness control?

Sharpness knob is a single knob attached to the NTSC IC:

https://i.imgur.com/eYqZfUW.png

And here in the schematic, it's pin 51 (in the lower lefthand corner)

https://i.imgur.com/memAgyH.png



So, I think I did approximately this by using the cursors on my scope to measure the ripples present on the power supply in various places, and it seems like it's somewhere between 250kHz-600kHz. The lines are more obvious on the left side of the screen, and basically disappear (on the raster) by the time they become about 350kHz.

I tried to dampen them by putting a 0.22uf ceramic cap near the 1ohm resistor that feeds the 12V supply on the video amplifier circuit. I succeeded in damping the flyback ripples from about 300mVpkpk to about 230mVpkpk, but it made zero difference to the raster that I could perceive.


This TV does NOT have a lot of coils in it, and almost all of the coils are in the RF section, which I am not at all using in any of these tests. There is a relay switch that isolates the RF side of the signal and switches the set to composite mode.

The non-RF coils are the choke in the main AC rectifier and three small transformers used in the power supplies, the audio and the deflection.

There are zero coils on the video input board and the RGB board which handles the OSD mux and color outputs to the neck board.

There is exactly one inductor on the neck board, L521, and it is between the 178VDC supply and the three collectors of the output transistors heading to the cathodes.


What does the fact that the Sharpness effects the signal say about that hypothesis? The Sharpness happens in the NTSC IC all the way back in the signal chain. Could it effect the lines on the screen if they were sneaking into the signal at the cathodes?

Sure I can try that. I have a couple of those small convergence strips with tiny weak magnets in the end. I can tape one to a wooden dowel and wave it around inside. They are already plastic covered anyway, and this is a small set so easy to do by myself.

Another thought I has was that maybe this is due to the nature of the set being a hot chassis that has an optically isolated composite video input. I had a thought that maybe this has to do with either the opto IC getting weak, or possibly a side-effect of the floating ground used for the opto-input section. Maybe this is all weird grounding issues caused by that arrangement?

You can see here that is has a separate little ground loop for the input:

https://i.imgur.com/rDw4mWZ.png

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Good Evening....

I would hope you could see the line pattern on the scope while syncing off the horiz.
pulse from wherever you wanted to pick it off.... And I can see your thoughts that
if you don't see it there, then you may think it's not in the video...
If that's the case, you should be able to still sync off horiz, and see the noise
on any of the power supply lines you want to look at.... Syncing off the
horiz would just make it stable.... I also agree 100% with your
estimate at the harmonic frequency..... You know what I mean - most
scopes have an external sync input, good in this case to be sure there
is a pulse large enough to trigger on.

If it don't have ext. sync, you could always put channel 2 on horiz, and
sync of channel 2, use 1 to find the noise.


As for the opto-isolator you should be able to take that out, pick another source
select and do whatever to get a blank white screen.... Or just remove it -

So if you feed this tv a signal from an rf modulator with no signal, or if you feed it a
signal from a dot generator with no or minimum dots, no lines, or color bars just
as blank as it can be, do you still see the vertical lines? same , or effected in
any way...? - I mean something blank, but with a sync pulse in it.... no color.

The one thing I disagree with it that for us to see that lines on the screen they
have to come from somewhere.... That scope picture you posted right under the
line " On the left side of L521, it looks fine, but on the other side of L521 it has
this 40Vpkpk 60Hz waveform. I guess it's the raster. It's probably normal, but
I haven't looked at that many different cathode voltages in my life. "

Where your cursor identifies a frequency of 60hz, those vertical tight lines - that
must be what is appearing on the screen - isn't it? Yah, each of those tight
lines is the individual scan lines and you can see they are of irregular height,
should they not be all equal for a white blank screen?

I guess you also have to be careful which ground you pick....? So if your scope
is completely floating.... Like battery power, what do you see if you look at
the ground.... Like hook your ground up to one ground, & scope the other,
and then switch it around....? Anything interesting?

Does it look like anyone might have removed shielding from anything?

And you see what Zeno said about that IC - it's got a few isolated circuits
within it..... Not all on a single Pringles chip.... Several GND's
Several VCC's.....


Good Night....


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Thanks for the thoughts here. I did once capture the collectors of the cathodes while syncing off the HOR pulse and I didn't see anything obvious there.

As an experiment, I also once put .082uf caps between the collectors of the video output and ground. I was given this experiment by someone to check for the banding in the video as the theory being that placing these caps across the video output should kill all AC components and the banding with it.

The banding in that case became lighter, but it was still there.

The conclusion of this experiment was that the banding must not be in the video, or is not fully in the video, and that it must be coupled some other way.

Currently a proposed idea is that it may be magnetic interference from the flyback itself and that I should pull out the flyback and extend the leads in order to move it around and see if that changes anything.

Do you agree that the caps across the video output collectors should have killed the banding if it was wholly present in the video?

.

"Do you agree that the caps across the video output collectors should have killed the
banding if it was wholly present in the video?" - No, because a cap in that spot, or
any spot will only partly reduce, or enhance any interference. You could only
completely remove it if you set a bias in the signal drivers, and removed
any possible signal from effecting the drivers, tube or transistor. Not
to ground the base, but bias it and cut the input signal So you don't
drive it into saturation, or cutoff.

I'm pretty sure the interference is from the Horiz circuit as the lines are stable
with respect to the horiz sweep. Is it magnetic? Not sure, that is why I thought
moving around a piece of steel might show something. Most likely it's
electronic, a harmonic that is not sufficiently terminated in this design,
or it is and a component is bad, a circuit trace is broken, ground broken,
something just allowing a harmonic large enough that you see it
on the screen.... Bad coil, cap, etc, around the horiz drive,
flyback, yoke, you name it, it's in that area, or something
is picking it up & sending it through the set.

The problem with the interference in the power supply is that it will be present
in all amplification circuits - even if they are biased on in steady state and
not doing anything else.... Think about a bad filter cap in an old 5 tube
radio, I'm pretty sure we have all heard it. Volume effects it a little,
if it has a tone control it will effect it a little, and being on a station
will effect it a little too. - But is it in the signal path?

I once had a white hum bar floating through a tv picture, Naturally I thought
it was a cap, so did everyone else... The set went around the shop till I got it
back and changed some tubes.... Turns out it was a heater cathode short
in one of the video tubes...


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