K7000 missing blue please help.

[ac3]

I have a K7000 19" monitor (19K7681) missing blue. I have tried replacing Q3, Q203, IC1 and I've checked R212 on the neck board. I've also reflowed all the solder on the base of the chassis incase there was any bad joints. Still no blue, I thought it might be the tube so I tested it on another K7000 (similar model) and there is still no blue and I know that blue works on that tube.

Using the CPS2 test/color screen the blue bar is missing but the background that should be black is blue. On the original tube the background is black but with blue scan lines. I can't seem to get the brightness down enough on the second tube but this shouldn't be an issue as it will be going back on the original tube if I get it working.

Adjusting the two blue pots on the side of the neck board does absolutely nothing, could one or both of the pots be bad?. Any help is very much appreciated.

Thanks ac3.

[shess]

Looks like you replaced the correct components according to the Randy Fromm flowchart.  I'd say locate a schematic and check everything else in the blue path.  You could try swapping the pots from another color to see if that eliminates the pot question.

Scott

[Kevin Mullins]

Check the pots.

Swap the color inputs.

Try a different game board source.

[ac3]

Thanks for the replys, I know the game board is fine but I did try another game just incase and blue was still missing. I swapped the red and blue input wires, this meant I had blue but lost red.

I will swap the pots next as suggested and report back.

[Kevin Mullins]

You could swap the entire neckboard if need be to at least test.
And the pots themselves can be checked with an multimeter.

I threw some pics and pointers out in this thread with a similar problem.
http://forum.arcadecontrols.com/index.php?topic=92162.0

You mentioned checking solder joints, so I'm assuming you checked the ones on the video input header pins already. (I've seen missing colors due to bad joints)

[ac3]

Checked the pots and they're fine, I am starting to give up on this one.

[SirPeale]

Thanks for the replys, I know the game board is fine but I did try another game just incase and blue was still missing. I swapped the red and blue input wires, this meant I had blue but lost red.

I will swap the pots next as suggested and report back.

If I'm reading that right that means you have a board fault and not a monitor fault.  If you swap the inputs and the problem travels, it has to be on the board side.

Or have I not had enough coffee yet?

[Kevin Mullins]

Well, it kinda contradicted itself the way I read it.

A. I did try another game just in case and blue was still missing (monitor issue)

B. I swapped the red and blue input wires, this meant I had blue but lost red. (board issue)

[ac3]

It's not a board fault, it is the chassis but I don't know where to go from here.

Edit: I've just thought of a better way to explain it. What ever color is connected to the blue pin on the monitor isn't displayed. But if I connect blue to the red or green pins it is displayed where red or green should be displayed.

[Kevin Mullins]

That clears it up. (monitor fault)

I would start from the video input and work my way in towards the neckboard.
You'll note everything leading up to IC1 is in threes....transistors, caps, resistors, etc.
There is a voltage check you can do on the "outputs" of IC1, just can't remember what they should be off hand. (approximate voltage or signs of life on the color outputs)
If there is nothing on the blue output of IC1 then you would backtrack towards the video input from there. (inputs on the IC1 and circuit leading up to it)
Then there's generally a series of resistors from the IC1 to the ribbon cable that leads to the neckboard.
Also check the four pin connector itself that goes from the main chassis to the neckboard. (usually three blue wires, one white) 

Going through all that will lead you up to the neckboard.
Can troubleshoot further from there if need be.


Also note, my personal experience is with the 25" versions, so there may be slight variations.

[ac3]

Not much progress really but after doing a bit more research it appears this chassis is a K7000A. I ordered C2068 transistors for the neck board going from the K7000 manual but the original was a TZ1034 which I cannot find a datasheet for. After comparing the new C2068 and old TZ1034 with a multi meter I am getting different results. I am wondering  now if the TZ1034 is bad or if it was fine and I've fitted a incorrect replacement. 

[Kevin Mullins]

Well, one sure fire way to test that transistor would be to put in place of one of the working colors.

i.e. put the original blue transistor where the red one is - if you still have red, then it's good

[ac3]

Sorted!  Thanks to everyone who replied for your help. Turns out the TZ1034 I replaced was fine and the C2068 I replaced it with isn't compatible. Worth noting that it's not just the lopt that is different on the K7000A.

[Kevin Mullins]

Turns out the TZ1034 I replaced was fine

So what actually "fixed" it then ?

[ac3]

Replacing Q3 (2N3904) is what fixed it.

[ac3]

After putting it all back together and moving it I have a new problem. 

The monitor is heavily magnetized and no matter how many times I turn it off and on the degaussing coil doesn't fix it. I've had this problem on Hantarex monitors and I've had to replace the posistor but never had it with a WG monitor. Doing a quick forum search it doesn't seem to be a common problem for degaussing not working on a WG monitor. Does anyone know what the problem might be?. 

I forgot to mention, I do have a degaussing wand but I've misplaced it and I'd like to try and fix it so the coil kicks in anyway.

[Kevin Mullins]

Keep in mind the degauss only kicks in when the monitor is cold.
So whenever I move a machine I put in in position and I let it sit there awhile before trying to turn it on. Then you can see if you still have a degauss issue.

Never had a problem with a K7000 though.
But I'm sure it could happen.

[SirPeale]

And the built-in degaussing only kicks in for a second anyway.  I made my degaussing ring from an old one on a TV.  Or you can try a corded drill, it generates similar magnetic waves, though not as powerful.