19" K7000 that I can't get vertically centered

PrairieDillo

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19" K7000 that I can't get vertically centered

I have a specific game that just sits up too high.

I've tried two identical cabs with the same 19" K7000 monitor and I can't get the image centered vertically. The put is just out of adjustment. Is there any way I can change a resistor or to give this vert center pot more range?

the Horz adjustment has a lead that you can move right, center or left but there's nothing like this on the vert adjustment.

Any thoughts?
 
Is your synch hooked up to the last two inputs on the chassis signal input header? I had a somewhat similar issue and it was due to the synch being hooked up to the second to last pin, switched over to the last pin and it was good to go. I'm sure this is probably not going to fix your issue but it doesn't hurt to look. ;)
 
do you have another 19" wells tube and yoke???

mabye the yoke is misadjusted/tilted. if you put this hassis on a diff tube and the issue s gone, well, there ya go.

if the issue follows the chassis then you could dig into it more..
 
I recall a Randy Fromm article giving this advice:

To shift down, parallel R83 with a 680 ohm resistor. To shift up vertically, remove R83 or increase value. Strange advice -- resistors in parallel decrease overall resistance, so you'd think that reducing the resistance value of R83 would do it. Not sure why he worded it that way.

Now, this is probably for 19" K7000s, and I have not tried it - just passing along the info.

Edit: OK, so removing R83 does NOT imply adding a jumper. Removing R83 implies creating infinite resistance. So, Increasing resistance moves the display up, and reducing resistance moves the display down -- as suspected. I still don't know why he didn't state it that simply. Again, I have not tried this, I am just coming to terms with what Randy wrote.
 
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I'll give it a shot. I happen to have a 680 ohm resister very handy!!!

I have 3 DD machiens side by side and they all do it with the Growl board.
 
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From the manual, looks like R83 is already a 680 ohm, 5% tolerance, 1/2 watt resistor. Make sure you use the same 1/2 watt or you might have a nasty smell to get rid of!

So, net resistance:

1/Rtot = 1/R1 + 1/R2 = 1/680 + 1/680 = 2/680 = 1/340

So, Rtot = 340 ohms. At 5%, that gives 323 - 357
A 330 ohm should do it by itself if you find that it works.

If you find that it's too low now, I'd say shoot for the middle. Parallel a 2k or 2.2k with the original 680 to end up with a new 507 - 519 ohm resistance. Or, if you just happen to have a 510 on hand, then you have a better resistor supply than I do!
 
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Thanks, that's helpful.

So this is what I found out.

All Double Dragons have R83 clipped at the factory. It must be related to the funky resolution of the DD board. It's crazy narrow also.
How funny is this... this is why I didn't think there was a problem! I was testing it all on DD cabs.
 
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isn't that what the Vert center pot is for. The resistor just sets the general range I guess. I just got Growl centered for CAX so now I'm happy.
 
Resistor probably sets a floor value. Two pots could be dialed to zero, which might not be tolerated by the circuit.
 
Figured I'd bring this thread back to life.

I'm having the same issue with a K7000 25", except I can't get the picture to go up high enough. On the 60-1 board I use to test monitors, It's centered perfectly at max "up" (horizontal mount). When I connect it to my PC (I'm going to use the monitor for a Daphne cab), it's about an inch shy of being centered at max "up".

I connected the PC to a 19" Sampo I just capped, and the horz and vert centering is normal.

I played around with the sync and that's not the issue. I also played around with the yoke,and that's not the issue either.
 
some K7000 models have this problem.
it is that way from the factory.

i have had plenty do that and have some in my games.

just one of the many revisions/changes they made over time.

i believe you can change one or two of the resisters in the vertical circuit to help that but i do not know witch one/s it is.

you may be able to use the 50/60htz pot to get the image where you want it.

Peace
Buffett
 
First thing I tried was the 50hz. I can adjust it to get the picture up where I need it, but at the cost of rollover, which gives the top 1.5 inches a brighter appearance.

The resistors are mentioned previously in this post. I may give it a shot or just swap it with one of my other games that it will center with.
 
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Hahaha

Buffet,

I just found a post on BYO arcade controls where someone had the same issue.

You replied to remove R83. Just as the post earlier stated. Guess I'll give it a shot after work.
 
shows you how long it has been since i have done the mod/change to that circuit.

it's cool that you found it.

please post your results.

Peace
Buffett
 
Well, that was easy...

I pulled the chassis, flipped it over to remove R83, and what do you now... There was a resistor soldered on the backside. I pulled the modded resistor off the backside, installed the chassis back on the monitor, and vertical centering is back to normal.

Case closed.
 
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