Wells K7400 Vertical Deflection Problem (pics Included)

[powerplay]

This is a Wells Gardner K7400 (P763). I have a Horizontal line in the middle of the screen. I have replaced many components which I will list. Most of these usually do the job to fix this problem but, I haven't had any luck. Here's the list:

D302
R402
U601 (Ic, Vertical Deflection)
U701
R303
T700 (FLyback)
D603
R627
C610
C603

I have also replaced the control board just in case along with a cable.  Tried another joke as well. All the above parts were replaced with new parts and all the parts mentioned on this paragraph were reinstalled on a working chassis to make sure they work and they do.  I am getting my+25V to my U601 pin 9 as required.  After all that still the same as the pictured included. Any help is appreciate it. thanks


Model of chassis

http://i687.photobucket.com/albums/vv234/Powerplay800/k7400-1.jpg


Error on screen

http://i687.photobucket.com/albums/vv234/Powerplay800/k7400-2.jpg

[qrz]

also check q602 for leakage or ce short.
and check c613, c616, c614 and r618, r613


qrz

[powerplay]

Thanks for all the help QRZ but still no change. I replaced Q602, C613, c616, c614 and r618, r613 as you mentioned, and no luck. i still have the same line. Anything else I should look at?

[Kevin Mullins]

I'm going to assume you've checked for obvious bad solder joints around the yoke pins and the yoke itself right?

[powerplay]

kevin, you got it!, I sure have. I think i can do a tatoo of this board on someone as many times I have seen it and gone over it lol. Yeah i done all that and still no luck.

[qrz]

try another output ic .
be cautious on your vendor.  many counterfeit semiconductors are beginning to surface   

qrz

[cgaw69]

Does your monitor have a remote adjustment board? I have a Kortek 25 in. that had remote adjustments and that the person before me installed it backwards on the extension cable. Resulted in the exact same condition you pictured. Not saying this is the case with yours. Just thought the info might help.

[Kevin Mullins]

I was going to suggest looking at the remote board or vertical pots as well.
Could have a bad or broken potentiometer.
Just another easy thing to check.

[qrz]

good point Kevin.   vert deflection is a "closed loop" .
which is why signal injection isn't an effective troubleshooting method in this stage .
a fault in the feedback loop , or elsewhere , will cause problems .
def have a look at the size/linearity pots.  it might just be that simple.


qrz

[powerplay]

Thanks for the feedback guys.....but as stated in my initial post, paragraph after the list of components changed I put:

"I have also replaced the control board just in case along with a cable.  Tried another joke as well. All the above parts were replaced with new parts and all the parts mentioned on this paragraph were reinstalled on a working chassis to make sure they work and they do.  I am getting my+25V to my U601 pin 9 as required."

The control board was put in another monitor board chassis and it works, I have also tried another one just in case from a working monitor board and still no luck. i will try another output ic and i will let you guys know.

Thanks