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Vertical ghosting lines on Iiyama CRT

retrogear

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Boy this is like being a detective. The RGB outputs are not on the CRT board and neither is the bias supply. I'm surprised the circuit side has the silkscreened labeling. That is great. Ok, referencing your picture #1 posted 8/29 at 105pm, the RGB video signals are the three shielded round black shiny cables in the bundle coming down to the left behind the metal. Do those go to a connector on the main board? I would need to see the circuit side of the main board where those connect and the surrounding area. I didn't think those black TO-5 case transistors would be the outputs because of the part# shown. Are there 3 identical transistors possibly mounted on heatsinks that are labeled R-OUT, G-OUT, B-OUT or something like that? I would need to see the circuit side of that area. Unfortunately, do you have a large metal shield on the underside of the main board? I hope not. Also that main board might slide out enough for a picture of it's circuit side. If it has the same silk screen wording it will be easy to trace.

Larry G
 

retrogear

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PS - To take the main ckt board picture you can set the CRT on it's face or on it's side. However, if you set it on it's side make sure there's enough side case to balance so it won't tip onto the CRT neck. That would be bad. Best would be to put the crt face down and slide the board up slightly.

Larry G
 

retrogear

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>This issue can also be caused by a low quality video cable.

Yes, it's possible but usually there is also smearing or streaks in the video detail as well or ringing lines in the character edges, etc. Not just the left side.
Is the cable built in to the display or an external cable? If so, you could try another cable just to be sure.

Larry G
 

Denniske1976

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I'm using the original RGB cable and I've also tried VGA cables from different makes... all the same result.

Anyhoo, I have to see to get the MB out this weekend because there's a whole metal plate below the screen, bolted to the two side panels that have hinges that grab onto the rear metal plate again... probably a case of taking it apart in the right order to get it assembled again. From what I can see there's nothing much more on the MB than what the pictures show, not even bottom side... there is however another PCB on the front bottom below the CRT but that looks to be the digital control (brightness/contrast/menu/power) for the monitor.
 

retrogear

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>there is however another PCB on the front bottom below the CRT but that looks to be the digital control

the problem wouldn't be on that board

>From what I can see there's nothing much more on the MB than what the pictures show, not even bottom side...

The purpose of looking at the bottom side is to see all the circuit traces which is the next best thing to a schematic.
Once I saw the circuit traces on the CRT board I knew how the RGB was handled there and which wires to follow back.
Wherever those RGB lines end up on the main PCB, each one will feed from a collector of an output transistor and there
will be a pull up resistor to a common DC supply. I was looking at schematics of other CRT displays online and it looks
like manufacturers went away from scan derived supplies and fed the RGB outputs from a main B+ supply. There is
always a capacitor filtering that point. The ones I see have a value like 10uf 160v. I think with the lack of components around
your HV transformer and a multitude of transformers, etc on the left side of your board that the RGB power originates there
but need to be able to follow the circuit trace to find the source. Again, if it's too complicated to get the shielding off it might
be best to just stop here. Also if the RGB power is fed by the main B+ then the problem might not get worse like I described earlier.
That capacitor does filter noise which would appear at the scan rate so I still think that cap could be the culprit.

Larry G
 

griffk

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It doesn't seem to get worse from what I can see... so uhm, open the thing up and try finding that 47uF/200V thingie?

If you open the case, !!!BE VERY CAREFUL!!! - do *not* touch any of the HIGH VOLTAGE circuitry, use rubber gloves if possible. Don't mess with the flyback or any of the large capacitors...

gwk
 

griffk

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I was a bit hesitant to open it up since there was some kind of Xray warning sticker on the metal cage but I took off the top and back so I could get some pics done. It all looks OK to me, save for some dust everywhere:

The X-Ray warnings are only for when it is ON, and only then for a long period of time--don't worry about that!

I would try taking a large "canned-air" blower, and clean the circuit boards and cables/connectors of ALL DUST -- it's surprising what can change capacitance and resistance -- clean it out and reassemble, then try it again to see if there is any change at all...

gwk
 

Denniske1976

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Will do, haven't had time to take it apart further yet. But I'll take it apart (hopefully) this weekend and clean it. See what that does... and of course take some pictures as I have it disassembled then anyways ;-)
 

griffk

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Will do, haven't had time to take it apart further yet. But I'll take it apart (hopefully) this weekend and clean it. See what that does... and of course take some pictures as I have it disassembled then anyways ;-)


While you are in there cleaning, reseat all connectors/cables you can reach safely -- might be a poor connection in there somewhere...

gwk
 

retrogear

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When you clean, if you are using a vacuum cleaner be sure and keep the motor of the vacuum a few feet away from the CRT. AC motors can magnetize the metal shroud around the CRT tube especially when the vacuum is turned on or off. The display has a built in degauss circuit to demagnetize the CRT but it can only correct small magnetization. If you use a dustbuster handheld type vacuum just be sure to not power on/off next to CRT. Also don't get too aggressive around the neck of the CRT tube because there might be alignment rings on it. Personally, I don't think dust would cause the problem but it doesn't hurt to clean up. However, a bad connection could especially ones that provide grounding or the plug that goes to the deflection yoke (the coil winding on the CRT neck). That would be pretty rare though.

Larry G
 

Denniske1976

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Well, a little late but here's an update... I cleaned all the dust from the inside and reassembled the screen again. And it could be me, but from a blue screen (DOS EDIT or WP 5.1) the lines actually seem less now, I'd say about 80% less and barely noticable. Can't test anything white now as I'm out of time. Also been fiddling around with my PS/2 Model 80 who had a dead floppy drive and I found a new one, another ALPS, unfortunately also won't read diskettes... I was planning on checking the lines while installing that thing, it's quite cool, with 4MB memory (2 x 2MB planars) and a 386/387 @20MHz ;-)

Anyhoo, it's dark again and I have to prepare some stuff for work. I'll check it again, but can't help that maybe there's some dust left where I cleaned that can get the other 20% of the lines away if I can clean it better...
 

H-A-L-9000

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What happens when you reduce the horizontal size? Will the lines stay at the same position, or move with the picture or move towards the left side?
 

retrogear

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>I cleaned all the dust from the inside and reassembled the screen again. And it could be me, but from a blue screen (DOS EDIT or WP 5.1) the lines actually seem less now

Again, I don't think cleaning has much to do with the improvement but if you are seeing improvement it's more likely a connection issue, especially grounding. I had a thought,
are there screws that hold the board to metal shielding ? You could tighten those. Some manufacturers screw the ground plane to the shielding to cut noise problems. Or are there metal clips clamped to the
shields ? Reseat them. Also unplug / plug in any connectors especially the connector to the yoke on the CRT or any video feed, etc. If metal shields are soldered to the board look for solder cracks, etc.
Also there might be metal brushes from the shield around the crt tube to the glass of the tube itself. You could wiggle those to reseat and clean dust from the bell of the CRT. If you have compressed air
blow around in there or reach in there with a small brush. Usually those are to prevent static buildup but could radiate noise. Be careful of leftover high voltage on the anode wire on the CRT. That's why just blowing air might be the safest.
We wouldn't want to jump start your heart :p

PS - on second thought forget about cleaning the CRT bell. I'm thinking television instead of display. That would cause RFI. Focus more on connections and grounding.
Try this, disconnect the vga cable and turn brightness up to light the screen. You might need a dark room to see. If you see any vertical bars / lines attach a picture.

Larry G
 
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Denniske1976

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Well, it's not dark here yet so I can't do the brightness thingie yet...

I did however reduce the horizontal size of the picture from the menu and the 3 vertical lines move with the size of the picture, always being close from the left side of the visible picture. So they don't stay in the same place.
 

retrogear

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>3 vertical lines move with the size of the picture

Yes it proves it's part of the deflection raster and being only on left side, I'm sure it's not related to video signal but just the horizontal deflection circuitry.
If you can get the screen to illuminate without a vga signal we might see the 'ringing bars' to prove it's not a video problem. You could do the photo under a blanket but don't leave on very long when covered
so it doesn't overheat. Unfortunately, a raster ringing problem is very hard to determine the cause and may not be repairable within reason. The only simple fix at that point
would be to watch the ring bars while you use a plastic stick to wiggle wires and flex the board to see if changes. Any ground screws like I mentioned ?

PS - can you adjust the width so it exceeds the edges? If your width control at max just barely makes the edge of the screen we could be looking at bad yoke tuning caps which also causes ringing.
Also possible a borderline power supply but that doesn't usually cause ringing.

Larry G
 
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retrogear

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>It can still be related to the supply voltage of the video output stage.

Yea, a schematic would definitely simplify this
 

Denniske1976

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Hi mr. retrogear and all the others ;-)

Well, after some time I finally got round to doing this thing this evening... opened up the monitor and while there really wasn't much to see as far as loose bolts go, I took apart the cage surrounding the electronics, and just tightened everything I could find that had either a ground wire attached or had the main PCB attached to the frame. Cleaned the electronics some more and closed the monitor again.

Guess what: IT'S ALL GONE!! I mean WTF?!?! (and believe me, with my OCD if there was even the slightest line I'd see it). There is ABSOLUTELY nothing disturbing about the screen anymore. I tried WP 5.1 and DOS 5.0 EDIT.COM as those have a blue background, tried some games and all is smooth and evenly colored!

Thanks so much everyone, it took me a while but I now have one of my favorite CRTs working again as I want to (and will use it with my 486DX2-66 computer). Just AWESOME!! :)
 
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