[SOLVED] Vertically mounted K4900 in need of some love

[the720k]

I have a Raiden Fighters II JAMMA cab I'm trying to fix up.  I should point out that the cab was originally a Leland Quarterback that at some point had been converted to JAMMA with RFII installed.  It has a K4900 chassis and an RCA 25" tube.  Have not yet gotten in at the angle required to see the S/N of the chassis. Hoping it's a later model.

The game operates fine, and the monitor works, but suffers from poor quality.  Dim colors, horizontal pinching near the center (vertical in its current orientation,) and nasty curve/spacing out on the left (or top, if it were horizontal.)  Where the pinching, spaces and curves occur, the picture is wavy.  This improves a bit with the machine being kept on and left to warm up, but never really goes away.

I've adjusted the RGB cutoffs and R/G drive pots on the neckboard, and this did improve the colors a great deal, though the other issues remain. 

I recently installed a 60-in-1 board that I can swap in and out whenever I want to mix things up a bit, and noticed the seemingly common fold over issue that many 4900 monitors run into with the 60-in-1 boards, which happens in the same spot that the image stretches out and distorts when RFII is installed.  The picture distortion/fold-back at this point gets way out of control, and renders many games unplayable.  I also noticed that the 60-in-1 doesn't fill the whole screen.  After the monitor has warmed up a bit, I still have about 3" of unused space on the right (bottom) of the screen.  This was reduced greatly when the RFII PCB was plugged in.

I read somewhere that earlier versions of the K4900 chassis will not operate correctly/give fold over problems at the top if they aren't using the correct yoke, and I am really hoping this is not the case here.  I don't think the RCA tube is original, but could be wrong, and it makes me wonder if someone built a frankenmonitor out of spare parts lying around, and threw it into this cabinet. 

I've played around with the V-Damp, V-Position, and V-Hold with limited success.  Still a bit of fold over on the 60-in-1, but a little less.  I'm waiting on a cap kit, but I have a feeling it will only improve things slightly. 

At any rate, I'm attaching a pic of the back of the monitor.  I lost the pics of the screen in action, but can upload if you guys want to see the symptoms.  I'd take them now, but it's -1 outside and I'm sure the garage is only a little bit warmer. 

Thanks in advance for any ideas!

[the720k]

Anyone?  My cap kit just came in today, so I guess I will do the recap, reflow some joints, and cross my fingers.  I wonder how many people on here have had issues with 25" tubes installed on K4900 chassis boards.  I'm not necessarily asking for people to give suggestions on what I should do (unless you're offering,) but some anecdotes would be helpful if anyone has any to share. 

I am aware that the K4900 chassis isn't exactly best friends with xx-in-1 boards, so I expect some issues, but hope I don't have a mismatched yoke and chassis.  If that were the case, I would be willing to trade my k4900 with a chassis compatible with my tube if anyone might be interested.

[the720k]

I'm in the middle of recapping the chassis as we speak, but ran into something I'm concerned about.

C311 in my cap kit calls for a 4.7uF 160v cap.  I just pulled a 10uF 160v cap from the board.     Hopefully someone here has experience with the K4700 and will see this before I finish up. 
 
Which should it be?  I have a 2061433-055 chassis.  Thanks!

EDIT: ...AAAAND... horizontal collapse.  Time to check my joints.  Hoping someone has an idea on C311 though.

[buffett]

a 10uf @ 160v cap will work just fine.

also if you want to replace that monitor and you are in the US i will help you find another monitor for your game.
i would like to have your yoke and chassis out of your game if you decide to change it.

you may never get rid of the curl on the 60-1 they are cheap crap.

Peace
Buffett

[the720k]

Thanks for the reply, buffett.  As the original cap didn't look too healthy, I went with the new 4.7uF in my cap kit, and the sun still came up the next day.

I had a chance to slip out to the garage this morning and found that the H collapse was a simple case of the PCB end of the yoke connector being loose.  I didn't want to stress the chassis too much, as there is nothing supporting the midsection of the board.  Lighting is pretty bad out there, so I couldn't see the pins still partially exposed.  Wiggled it back on and I now have deflection.

At any rate, the cap kit did the trick for most of the issues.  I need to tweak my focus, B+, and black level, but it's a huge improvement.  No jitters, bad colors, curving, etc. to speak of.

However, I noticed a bar on the screen on both the RFII and 60-in-1 board when I powered it back on for the first time.  I adjusted the V-Damp, V-Pos, and V-Hold until it mostly went away, but can't get close to a full picture so far without the horizontal bar.  I only had about 10 minutes to play with the pots before I had to leave for work, so I wonder if I just need to spend a little more time adjusting. 

When I get some more time this evening, I'll set up a mirror and make more adjustments.  I understand the V pots are all dependent of one another, so I probably haven't even scratched the surface in terms of pot positions. 

Thanks for the offer in regard to the monitor, by the way.  So far, I'm optimistic about the future of this thing in my cab, but if I end up calling it quits and going with another chassis, I will definitely kick it your way and take you up on your offer to help find a compatible chassis/yoke.

Oh, and I agree with you on the 60-in-1 boards.  They are cheap Chinese boards, and I had no expectations of it being perfect.  Just thought it would be fun to drop in once in a while rather than go to the trouble of doing a full-on MAME setup.

Attaching a few pics to show progress so far.   The first two show it with the bar, and the third is with the issue adjusted out.  The bars you see on the last pic are just from the refresh being captured on my camera - not visible in person.  the middle pic is supposed to be centered like that - it's a shot from the attract mode, which expands when the text finishes rolling.

EDIT:  Searched around a bit and found this particular message in this thread:  http://forum.arcadecontrols.com/index.php/topic,28665.msg241551.html#msg241551

Ken talks about the chassis mentioned in that thread as being a 25K5515, which is the 25" version of the K4900.  The 25K5515 is definitely a medium-res, though, and mine is without a doubt displaying at 15kHZ.  The OP also had 15KHz, so perhaps this is a K5501 instead?  That chassis looks identical to mine, uses the same exact tube, and as per the post I linked, it used a 10uF 160V cap at C311.  Mystery solved, perhaps?  I think I'm going to go ahead and order a brand new 10uF 160V cap now and see if it resolves the vertical deflection problem.   

Funny side-note, when this cab was picked up at the auction, there was a Lethal Enforcers cab right next to it.  Almost bid on it.  Who knows, maybe I'd have two of these oddball monitors if I had.

[buffett]

glad the deflection issue was an easy fix.
it is easy to over look that connection on many different chassis.

you cannot adjust your B+ on that chassis, it is a fixed circuit.

you can adjust everything else.

once you do a complete color and wite balance to the monitor that may or may not help the bar.
lets hope that it does.

if you need a basic tutorial on how to do it.
you can use my video i made. i am using a K7000 but the concept is the same on yours you just do not have a contrast pot on that chassis.
skip to 18:00 into the video to see how i do it.



no prob on the offer i would like that setup so i can repair theses rare beasts for people.
and to preserve and document info in them to help others that have them. there is verry little known about them.
they are essentially the same as their 19" brothers but some of the parts are different and to my knowledge there is no manual for it noting the changes.

yup i would not get your hopes up on the 60-1 PCB people the world over have many different problems with them.
play it for what it is and find the real thing in time.

i have heard of them being std res and med res but never had the chance to find one to compare them side by side to know what the differences are.

good luck on your progress and keep us posted.

Peace
Buffett

[the720k]

Nice tutorial on balancing the color/white.  Will definitely use that method when I get to that point. 

After more research, I'm a little more certain that this is actually a K5501 chassis.  From what I can find, 01 means standard res, and 15 means medium.  Searching the specifics of my chassis me in that direction, specifically that the number silk screened on the bottom that reads "DBQ 2061433-055."  Finding some posts on the Internet with people having a 25" tube and that specific number on the board.

The bar shown in the pic varies depending on my adjustments of the vertical controls - the most severe is shown on the first image, and the lesser one is shown on the second.  Surprisingly, the game boards don't make much of a difference in severity.  If you notice, the bar is actually pinching/stretching the vertical image in the first pic, stealing image from the bottom of it and stretching everything above it.  If C311 is supposed to have a 10uF cap for 25" monitors as Ken Layton said, I'd bet this is what happens when a 4.7uF is installed.  Makes sense to me, anyway, especially since C311 is on the vertical circuit and it was the only cap I received in my kit with a different value than what was on the board.

Sorry to be so wordy, but I'm pretty intrigued by this mostly undocumented monitor and the prospect of repairing it.  So far, I will probably keep it, but if you'd like any detailed pics of the chassis when I get it back on the bench, or any more info on the components, I'd be more than happy to snap some for you. 

[the720k]

Still waiting on my cap - hopefully will be in tomorrow, but I tweaked the controls a little more, and followed buffett's suggestion for balancing out the white.  Kind of tricky to do on my chassis without having a brightness/contrast, but adjusting the black level on the chassis and screen on the flyback made it clean up pretty nice.  Played with the cutoffs and drives a bit to fine tune the colors. 

The tube is gunning down, though.  I had to crank the R/G drive way up to get acceptable color levels.  These pretty colors will be slowly fading away in the next few years I'm sure unless I get a rejuve, and since there's some moderate burn-in, I might as well swap it out one of these days. 

In the meantime, the picture is great so far, though the blue is bleeding a bit and the green could probably be worked up a tad:

[buffett]

it's looking better for sure.

it looks like the red is a little high but that could be just the difference between the two games.

Peace
Buffett

[the720k]

Yep, the 10uF cap was exactly what I needed.  Replaced it last night and I now have full display.  Thanks for the help!   

I'll tweak the colors a little more tonight, but I'm almost there.  If you want any specifics on the chassis or yoke, please let me know and I'll snap some photos, buffett.  I have some minor repair work to do on the cabinet itself over the next few days before I close it up and push it in line with the rest of the cabinets, so there's a window of time when I can easily gather whatever info you'd like about it.

[buffett]

glad it did the trick.

that's cool hit me on my email.
what i want info wise can be posted here after everything is said and done.

my email address is on my site.
thearcadebuffett.com

Peace
Buffett