Sony KV-9200 Uneven Raster

[vol.2]

I'm working on my KV-9200, and I am seeing that the screen is a bit brighter on the right side of the raster.

I don't have a lot of sets this old, so I'm not super familiar with the H sweep setup on this thing, and I don't know if the uneven brightness is my fault for setting it up wrong, or it's just due to aging components.

If it's my fault, then that's down to the fact that there is a static horizontal convergence grid inside the tube, and I don't really know what to do with it.

The Sam's say there should be either an HSTAT control OR Hor static convergence rings, but I think my set has both of them, based on the number of rings, and what those rings do.

I have Purity plus two sets of rings besides, and all four sets effect convergence differently.

Basically, when I did it, I tried to keep the HSTAT knob as central as possible, and adjusted for the best convergence and geometry, etc. All in all, it looks pretty damn good outside of the uneven raster.

But could this be due to overcompensating in one direction or the other with the rings or the HSTAT control?

The other thought I had was that maybe something in the geometry controls is throwing it off, because the H yoke ends terminate in the geometry circuit on one side and the convergence circuit on the other side. I would estimate based on that the H sweep is tied to those components, and any imbalance in the two sides of the H yoke could manifest as an uneven scan.

You can see below in my picture where the two ends of the H yoke terminate. It's very different from what I'm used to. I don't even see something like an S correction cap.

[zeno]

C 524 most likely perp. Common to ALL brands.
Zeno

[vol.2]

Originally Posted by zeno

C 524 most likely perp. Common to ALL brands.
Zeno

Hi Zeno. Thanks for the reply.

I replaced C524 already. I went through and checked all the lytics on this set a couple years ago, and everything in the H/V sections was way out and got replaced.

Taking it out and looking at it, I notice that the value is different from the service manual. Manual calls out 4.7, and I have a 10 in there.

Chances are I wouldn't do that unless a 10 came out of the board though. I tend to go with the PCB over literature.

But I guess someone else could have put it in there before I came around.

I can confirm that swapping C524 out for a brand new 4.7uf cap did absolutely nothing. Also tested to see if the HSTAT or purity rings had any effect and they do not. I was going to test the other rings, but I doubt they will have any effect, and I'm getting tired. Can get back to it tomorrow.

[Alex KL-1]

Very intringing. If the video output PSU cap are not the culprit as you already checked, I can assume that the bright only will change with:
Bad linearity, compressing the sweep in one direction, but then the image will be distorted;
Some cap for the video coupling or decoupling in the video processing circuits?

[vol.2]

Originally Posted by Alex KL-1

Very intringing. If the video output PSU cap are not the culprit as you already checked, I can assume that the bright only will change with:
Bad linearity, compressing the sweep in one direction, but then the image will be distorted;
Some cap for the video coupling or decoupling in the video processing circuits?

It could be. A failed component would be a good fix.

I'm mostly worried that the voltage multiplier is weak and it's not delivering even voltage across the sweep. Though I don't know if that wouldn't also effect the geometry? There doesn't appear to be any geometric distortion matching up with the brightness halo.

[Alex KL-1]

Originally Posted by vol.2

It could be. A failed component would be a good fix.

I'm mostly worried that the voltage multiplier is weak and it's not delivering even voltage across the sweep. Though I don't know if that wouldn't also effect the geometry? There doesn't appear to be any geometric distortion matching up with the brightness halo.

I cannot imagine that, the "tripler" furnishes the requested final voltage only at flyback pulses (last diode blocks from sweeping time), and CRT cap ("aquadag"+glass) holds it for a line time.

And is pretty rare to a CRT having a dim lateral zone (normally are the borders or, more rarely, in the center).

[zeno]

This one is a little different. Usually the neg of that cap goes to GND.
Look off the negative, it goes to the #1 130 V source. There is usually another cap to GND from the 150.. Probably on the PS part of the schematic.
HINT on most Sams there is chart showing how many points a source goes to
This is very handy at times when you are unloading things.
Anyhows the value of cap I have seen is 4.7 OR 10 MFD. I have seen a few
open coupling caps in the video chain on these sets.
To wrap it up can you post a pix of the symptom ?
73 Zeno
LFOD !

[vol.2]

Originally Posted by zeno

This one is a little different. Usually the neg of that cap goes to GND.
Look off the negative, it goes to the #1 130 V source. There is usually another cap to GND from the 150.. Probably on the PS part of the schematic.
HINT on most Sams there is chart showing how many points a source goes to
This is very handy at times when you are unloading things.
Anyhows the value of cap I have seen is 4.7 OR 10 MFD. I have seen a few
open coupling caps in the video chain on these sets.
To wrap it up can you post a pix of the symptom ?
73 Zeno
LFOD !

Thanks for the guidance Zeno. I'll look into the PS. Here are two shots of the raster and one bit of the H yoke on the Pincushion section.

The PLUGE shot shows that the right side is brighter. You can see that the right side white bar is visible, but the left side is not. I took this shot because it's too hard to capture the edge glow on the right side with my phone camera. I tried everything I could to make it go away, but none of the geometry controls or puritycontrols change the brightness imbalance. Pivoting the yoke doesn't matter either. The purity is good in my opinion. I degaussed with a good ring as well.

The other shot shows another symptom; the geometry is messed up towards the top. It becomes noticeably wide on the top side of the image, and then pinches back in again at the very top. The pincushion control only does barrel correction, but this is keystone distortion. It also appears that the pivot point for the EW is too high up, or there is some linearity problem. I drew a Red line where it appears that the pivot point is. I mention this because it appears that the geometry control is directly coupled to the H Sweep if I read the circuit correctly. Seems like the H Yoke goes between the CONV OUTPUT transistor and the Pincushion pot, and then to the base of PINMOD transistor.

Also of note is that the Pincushion barrel correction seems to be towards the end of its travel; the picture is biased towards pucking in on the sides. The barrel correction seems to be pivoting symmetrical in the middle vertically though, unlike the keystone (which seems to be too high).

I took some voltages around the PINMOD transistor, and I see that the voltage on the base and emitter are too high. Almost 115VDC on the base and 114V on the Emitter. Should be 110 and 109. The AC waveform on the base is more or less correct at about 10.6V pkpk.

[vol.2]

Originally Posted by zeno

Look off the negative, it goes to the #1 130 V source. There is usually another cap to GND from the 150.. Probably on the PS part of the schematic.

I'm assuming you mean C522? It's been replaced. I replaced all the lytics. Almost every single one was way out or very high ESR or both.

[zeno]

C521 common on old Sonys. Same hourglass symptom. C-1 is in // with it
but not on all. Probably hung on the etch side of the PCB.
C522 is the "other" cap for shading, jail bars etc.
Good Luck
Zeno

[vol.2]

Originally Posted by zeno

C521 common on old Sonys. Same hourglass symptom. C-1 is in // with it
but not on all. Probably hung on the etch side of the PCB.
C522 is the "other" cap for shading, jail bars etc.
Good Luck
Zeno

So, I think I figured it out. Q511 seems to be pulling down the 130V on the other side of the flyback winding. I measured the flyback and the windings are spot-on, so I think it's okay.

Going to pull Q511 and see what the fuzz is.

Ok. No. this didn't really change anything for whatever reason.

The transistor was ok, but there was a ceramic disc cap that had gone high ESR across a diode on the other side of the collector. Replacing the disc cap brought back my 130V at the collector, but it didn't seem to make much difference.

Also of note is that the VSIZE and HSIZE pots are close to the end of their travel.

[vol.2]

Okay. I think I finally figured it out. Hopefully.

The HOT is very weak. I realized that it's barely conducting, and I'm having to compensate for the screen width and geometry by pushing the controls all to one side.

Testing it in circuit, the DC voltage of the HOT is 1.7V and it should be 108V. I didn't think that this could actually happen as I figured it would be completely dead if the HOT was so weak, but I guess this design it just acts as a boost or something rather than being the primary generation of the horizontal signal. It's weird that the geometry controls were actually capable of compensating for the size problem.

Going to get a new one, but it's a weird old package. 2SC1034. Not sure how long it will take to find a good replacement.

[Popester]

Actually I didn’t think the second photo of the set looked too bad. Some of that bowing of the picture lines you have highlighted look like pincushion circuit issues. Might want to replace electrolytics in that circuit.

[vol.2]

Originally Posted by Popester

Actually I didn’t think the second photo of the set looked too bad. Some of that bowing of the picture lines you have highlighted look like pincushion circuit issues. Might want to replace electrolytics in that circuit.

All of the electrolytics have been replaced. They all tested way out and some of them were open or had destroyed legs.


In any case, I'm pretty sure I found the smoking gun. If you look at this portion of the schematic, I circled where I found a missing voltage on the collector of Q512. It's called the convergence output on the Sam's, but the SONY service manual calls it the HOT. It's supposed to have a 750Vpkpk signal on it, but it doesn't get anywhere near that high, and it's supposed to be 108VDC, but I only measure ~1.6V. There is about 114V present on the other side of that inductor.

Amazingly, there's enough travel in the screen geometry controls to bring it up to about the correct size when the HV Size are at their full travel, but I think this is why the geometry is messed up, and also why there is an uneven brightness on the raster (because I have to use the HCENT to shift the screen all the way to one side).

I found a transistor to replace it, but it will be some time before it comes in the mail.

[Alex KL-1]

1.6V with the set on? Very strange. Or the DMM are playing havoc with superimposed waveform, or really it have something fishy in Denmark...