K7500 U701 LA7850 IC pin problem

railwarrior

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Replacing U701 on a K7500 chassis. I had a trace lift and break on PIN 15 - Vertical Drive Output. I am looking for a place to jumper it, but there doesn't seem to be anywhere on the pcb this pin connects to. Pin 14 has no line of top of the PCB incating were the trace is, but it is ground pin according to the schematic.

Any help would be greatly appreciated.

la7850.jpg


u701.jpg
 
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Pin 15 is not used, which is why it's not connected. It's not uncommon when replacing it to have the pad come off. Don't worry about it. It's just an example of the crappy trace bonding WG's manufacturer used during that timeframe...
 
Progress?

Well, I've gone from this:

023.jpg


to this:

034.jpg


I have capped this chassis, replaced U601, U701 - Reflowed solder, check connections....

R305, D303 seem ok. Maybe, I should replace them anyways?
 
almost looks like it's the wrong resolution. you're aware a K7500 is a medium res monitor, yes?

it's also worth noting the horizontal hold pot is on the chassis itself and not the remote board. I swapped a K7500 to another Blitz cab and that was a required adjustment lol

but yeah, looks like a sync issue to me now.
 
don't I feel stupid...

In the course of fighting these things and taking them in and out you sometimes miss a step. Well, I sure did.
I forgot to plug back in the remote board!

035.jpg


Now I just need to tweak it. Thanks for all the help!
 
very fucking interesting. I guess cause that H-Hold pot's on the chassis and not the remote it will do that (as opposed to the horizontal line).

but yeah, live and learn. I love stupid solutions. lol
 
great...spoke too soon.

So, I let this thing run for a while and:

038.jpg

037.jpg

036.jpg


I had to bottom out the focus (all the way left) on the flyback just to bring it where you can read it.

Is that what is crapping out? I can't seem to adjust the washed out pic...sub contrast on chassis doesn't help. I am going to remove the glue and adjust picture on flyback and see what happens...
 
if the focus walks on its own then you're looking at a failing flyback. that's the bad news. these were just all made shitty. :/

I never messed with that sub contrast before. I always noticed that pot but never did anything with it. weird

EDIT: what's the deal with those diagonal lines? is that the camera doing that or does it actually do that?
 
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Those lines are from my crappy Iphone 3G...
I removed the glue and adjusted the picture knob on the flyback down and then brought it back up. It looks good...for now...played a whole round.
I'm going to let it run for a few hours and see what happens...
 
yeah, if Screen/G2/master brightness or focus walk on their own, the flyback's dying. if you intend on keeping it for awhile you might as well replace that anyway.
 
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