K4600, distortion/artifacts top of screen

[ElectricDreamz]

have had a K4600 in my possession for a couple years. never seen it work properly myself, but before i began work on it, it powered on but nothing more.

recently re-capped it, and replaced black level pot, axial cap, and filter cap. got everything reconnected, but could not sync to save my life. B+ measured at 127.5, i adjusted L351 to no avail, reflowed solder on the XY board, etc, still could not sync.

so i grabbed an old spare XY board and swapped it in, and after adjustments it syncs nicely, however ...

while everything else looks good, dealing with video distortion at the top of the screen. i've already hit what i think are the usual suspects here, curious if anyone else has seen something like this

 

[mecha]

that's foldover, did you try reducing the V. Size?

 

[ElectricDreamz]

coulda sworn i did, and the result was just losing real estate on the tube (small image relative to the overall screen) not actually cleaning that top of the screen up ... but i must confess, with the several re-adjustments and the swapping/re-flow between XY boards, i should re-confirm

that's foldover, did you try reducing the V. Size?

 

[in99flames]

You may have to play with the Vsize and Vpos to get it right but as Mecha said, that is foldover. Literally the image has folded over itself. I had it happen in my Neo geo cabinet on the horizontal end though. Sometimes it can be a pain to get it just right when trying to maximize screen real estate. It was with my Neo!

 

[ElectricDreamz]

lest i overlook the obvious, i cannot find a Vertical Position pot or post/jumper on this chassis. the frame is telling me this (K4601/2):

and while i'm aware not all of the adjustment locations are labeled here (like the black level pot, L531, etc), i'm stumped regarding anything allowing me to push that picture up or down the screen. what am i missing here.

Vpos

 

[Phetishboy]

I have this exact thing happening with a 4600 right now. And yes, reducing the size fixes the top but I lose an inch and a half on the bottom.

 

[mecha]

should have V center posts on the deflection board, not XY board. you know by the H center. I admit I don't have a very good mental picture of the 4600 in my head cause I've never had this problem with one LOL

 

[ElectricDreamz]

I have this exact thing happening with a 4600 right now. And yes, reducing the size fixes the top but I lose an inch and a half on the bottom.

like so?

here, it is almost unnoticeable unless you're intentionally inspecting it for issues. but then as we ramp up the Vert Size ...

there's some soothsaying so-to-speak when it comes to making the several necessary geometry and color adjustments of any CRT that's seen service and age, but now i'm really just hoping it's some hidden (or not so hidden) Vert Pos jumper/pot i'm missing

 

[mecha]

did you try it with an actual game? I think TPGs are bullshit. LOL

 

[Phetishboy]

 

[mecha]

why do you have a 4600 in a Bubbles though?

 

[Phetishboy]

why do you have a 4600 in a Bubbles though?

Cuz I don't have an extra 4900?

 

[ElectricDreamz]

the TPG's debatable equivalence to bullshit aside, it's not the TPG causing that top-of-the-screen interslice horizontal vaporwave aesthetic to happen

behind what super-secret hidden chamber of the K4600 chassis are the Vertical and Horz positioning controls??

did you try it with an actual game? I think TPGs are bullshit. LOL

 

[mecha]

WGK4600 Vertical Centering...How do you do it?

rec.games.video.arcade.collecting.narkive.com

KenLayton to the rescue again

 

[ElectricDreamz]

THANK YOU, too tired to try this tonight but will hit it first thing AM

WGK4600 Vertical Centering...How do you do it?

rec.games.video.arcade.collecting.narkive.com

KenLayton to the rescue again

 

[ElectricDreamz]

a few things ...

i pulled the main board, and scoured it (visually-speaking) on both sides, and i'm not convinced P604 (or any other positioning adjustment hardware, for that matter) exists on this board. also saw this ...

WG-4600 no go!!!!

You all ever write code? Old school PASCAL, Cobol, Fortran, Perhaps some good 'ol C. What does this have to do with my monitor? Ever fought to get something to compile for what seems like forever only to have someone walk up behind you and almost instantly say..Oh, don't forget your semicolon...

forums.arcade-museum.com

and i'm kinda wondering if that's the kinda chassis i'm dealing with here. due diligence being what it is, i spent several minutes playing with L351 and the adjustments on the XY board, and while we can dial in the width beautifully, no matter the tweaks to the above, the vertical remains invariably incorrect and stupid.

reflowed solder on the main board as well (had not done this previously), but still no change

 

[bitburn]

Earlier K4600's didn't have vertical raster position adjustment. Be curious if could duplicate by manually jumping in a 1.8kohm resistor.

Early:

http://www.arcade-museum.com/manuals-monitors/Wells%20Gardner%20K6401_Manual.pdf

Later:

http://www.arcade-museum.com/manuals-monitors/Wells%20Gardner%2019k4600%2019k4625%2019k4675%2019k4676%2019k4677%2019in.pdf

First I would check R611, R612, R613 for cold solder joints and proper ohms.

 

[GA61XX]

should have V center posts on the deflection board, not XY board. you know by the H center. I admit I don't have a very good mental picture of the 4600 in my head cause I've never had this problem with one LOL

V center pot & or V center pin/tabs not on all K4600 chassis

 

[Mathsjester]

I know I'm bumping a really old thread, but did this ever get fixed? I'm dealing with the exact same issue with my k4600.

 

[Mathsjester]

Just in case anyone in the future stumbles across this thread, I seem to have fixed the issue on my end.

All of my transistors in the vertical circuit tested good, but I chose to shotgun them just in case. I swapped out the vertical size pot because I've seen it cause a similar issue in other monitors. I also removed all of the old solder from the header pins and reflowed them. No change from any of that.

One thing that I noticed while reflowing the header pins was that the solder was not adhering very well due to oxidation of the pins (continuity tested good with a multimeter, however). Several sessions of cleaning the inside contacts of the header as well as reflowing the header/rest of the board a few more times and I no longer have partial collapse, or whatever this problem is. I suspect that the oxidation of the header pins introduces enough voltage drop in the vertical circuit to throw things off. I also noticed that the issue sometimes returns when I first turn it on, but things snap into place (all at once, actually) after a minute or two.