Help with WG K7500 Issues

[mclovin]

Hello I have a Golden Tee with a Wells Gardner K7500 and here is what is going on. When you first start it up cold, the color is good but the vertical proportions are off, the bottom of the screen is shrunk and the top is a bit stretched. Then when it warms up the vertical proportions get better and the colors start slowly washing out and gets extremely blurry after about 9 holes. See the pics and let me know where I should start. Would a CAP kit fix this?

[grantspain]

yes could be one or two caps causing this,bad solder joints could also cause this

[mclovin]

Here is a better pic of what is happening before monitor warms up. Do you know what caps cause this issue?

[baritonomarchetto]

It's a vertical linearity issue, so check capacitors and solders around the vertical deflection IC and check the vertical linearity potentiometer solders.
Giving that you have a loss of focus, i would change alle the electrolitic caps. If it doesn't solve, the flyback would be my next candidate.

[mclovin]

I'm a total idiot with this stuff, where is the vertical deflection IC located? And the electrolytic caps?  Where are they, would they come with a cap kit? Thanks again!

[baritonomarchetto]

I have not the schematics by hand for the IC, but if grantspain or someone else dont pop up, i will check for you. For the electrolitics... google is your friend

[grantspain]

caps i would change
607
613
610
615
616

[mclovin]

I've ordered a cap kit, I will post my results. Thanks for the help so far.

[mclovin]

Hello again all, I purchased and installed a cap kit, thought everything went well until I've somehow made it worse. This is all I get on the screen now. I have read this seems to be a sync issue. Anyone know what I could have done wrong here?

[baritonomarchetto]

Horizontal sync issue, yes. Has it worked after the cap kit, even briefly, or you got this image immediately after the cap kit? Acting on the horizontal frequency pot has effect?
In any case double check your work first (wrong specs cap, reversed cap)

[grantspain]

when you change caps the pots will probably need a tweek,try your horizontal frequency pot before doing anything

[mclovin]

Before the cap kit I had a picture, immediately after my handy-work it is scrambled like in the picture. I took it apart and checked my work, everything seems fine to me. I also tried adjusting the horizontal hold pot, and although it is difficult to do on my own, i made minor adjustments and then checked the screen and it did not help. Now i'm really stuck on what to do.

Now im really stuck what to do. One thing the cap kit included all caps except the main filter cap, and there was a major difference in the 10uf 50v BP cap in the kit from the existing one. The one that was installed was a very large cap and the one that came in the cap kit was tiny. I did put the small one in its place, so I thought maybe that had something to do with it so I just removed it and put the old large one back and it is the same problem.

Thanks everybody for the help. What do I do from here?

[grantspain]

check you have not bridged a trace somewhere with your solder work,maybe even a broken trace-depends on how good you are at solder work

its not filter cap-or incredibly unlikely

[mclovin]

Yeah I tried that, worst part is I also tried to re-solder many other areas that looked bad as well. I just bought bought a  capacitance tester so I will go through them all and remove them one by one again to check everything. Not sure what else I can do. I had some issues with the pincushion, could it cause issues like this?

[baritonomarchetto]

Before replacing every single cap is good practice to check if the new cap has the SAME capacitance and SAME OR HIGHER voltage rating of the old one. Dimension doesn't matter (to some extent) in this case because caps went smaller and smaller in time.
Unfortunately cap kits are "standard" for the sake of sellers mental sanity and frequently have some cap of wrong spec and/or caps for a single rev of the chassis (it was common to change some cap value from the factory and made some revision of the chassis pcb during the years).
You must be 100% sure your new caps are of the correct nominal value.

[grantspain]

and its vr701 you are adjusting for horizontal frequency?

[mclovin]

Yes it was the vr701 h-hold pot. I think all the others are covered with a hard glue of some kind.

There were a couple of caps I replaced that were 50volt, but I replaced them with 25 volt based on list provided with the cap kit. I just assumed that the monitor had 25 volt caps replaced previously higher 50volt ones.  Unfortunately I don't remember which 2, where can a find a list of cap locations with voltage and capacitance  that are supposed to be installed and I can cross reference with the sheet o got with the cap kit?

[grantspain]

imo you should download the schematics and go through every cap value you installed

it looks to be more of a frequency fault than sync but it could be the latter,i would suggest looking at c712 first and the caps around u701-check polarity and rating

[mclovin]

Checked c712 and it was fine. I did find something strange when I was checking my soldering and traces C734 has continuity between the cap both sides. Both traces have direct continuity to ground. I assume this is not correct?

[baritonomarchetto]

Unsolder the cap and check the two legs for continuity.

[mclovin]

I did and there is continuity. Both legs are to ground. I followed the traces the best I could and could not see anything obviously shorted out.

[mclovin]

I traced it back to a 1.2ohm resistor at location 301, so I tested it and it looks like my continuity tester just makes the beep at that low resistance. I will keep searching.

[baritonomarchetto]

That's why i told you to check for continuity between legs out of the circuit.

[mclovin]

Yes there is continuity between with cap removed.

[baritonomarchetto]

If you have continuity between cap legs, your cap is shorted and must be replaced

[mclovin]

Looks like I have no choice but to give up on this and get an LCD. I'm sure the problem has nothing to do with the caps, I may have messed something else up along the way somehow. Probably something simple but it's like a needle in a haystack.

Thank a everyone for your help!

[mclovin]

Ok I finally got it just as I was giving up !!!! It ended up being a broken plug and wire to the remote P903 adjustment board. After all the hours I spent removing all my caps again and tracing everything.

Now the monitor has excellent colour and there are no more issues with the vertical linearity issues!!!! Cap kit fixed it. The only thing now is after it warms up for a while it seems to start washing out a bit, until I adjust the fly back just slightly. I will let I try for an hour or so and see how it makes out.

[mclovin]

So when the monitor warms up it goes a bit out of focus. It can be corrected with a slight adjustment to the fly back, but when it is cools down it is a bit fuzzy again unless I adjust the flyback focus to where it was. Does this mean the flyback is going? Is there anything else I can check?

Thanks again for everybody's help! This is great, I am slowly learning!

[baritonomarchetto]

There could be a component going out of specs when the monitor warms up. It could be in the power supply circuit or in the flyback itself. Check if your B+ have some drift warming up first.

[grantspain]

it could be a bad pot on the flyback or a dirty crt socket

[mclovin]

Thanks again for the replies It looks like a have to google what it all means. I could live with it like this but it is perfect once the focus is just slightly adjusted in either the cold or hot state. Will google the b+ drift, cleaning the cry socket seems easy enough to try, and I assume a bad pot on the flyback will require a new flyback?

[baritonomarchetto]

Correct: generally fkyback pots and main body cannot be disassembled. If it was mine, I would not change it before the other tests.
Anyway, measuring the B+ is an operation to be done with the monitor turned on so, if you don't feel confident, have it fixed by someone who knows where NOT to put his hands on

[mclovin]

The B+ at tp202 is reading a steady 121.0 dc volts for an hour without much change.