Post by: asantora on December 12, 2016, 06:30:46 pm
Picked up a Rival Schools cab (really mk 2) with a 25 inch monitor. CRTs were never an area that I explored before, but after taking the machine home as-is, I was crushed to find that the colors were off. For the most part all screens have a strong blue tint to them. So, I tried a little troubleshooting and now I'm hoping past karma from this board will repay. Things that I tried:
1. First thing I did was adjust the pots on both the chassis as well as the neckboard, no luck.
2. Disconnected the jamma harness and reconnected, nothing
3. Removed the neckboard and reattached, nothing (note, the light isn't very bright in the neck)
4. Broke out the multimeter and pretended I knew what I was doing. Moved to continuity check and touched pins in jamma and connection on chassis and heard a beep for all colors.
5. Broke down, took some pics and looking for help. The test screen shows that red is drastically missing.. note, there's a little something there that doesn't show in the pics.
Based on my research so far, I have a sharp image chassis? Which uses the k7000 cap kit. Not sure what the tube is, but pics are attached. Thanks in advance for any help, looking forward to learning new things.(http://uploads.tapatalk-cdn.com/20161212/3c0d9edfe8a346994b819f116855e15c.jpg)(http://uploads.tapatalk-cdn.com/20161212/1051d8dc0991156a92a140925620405b.jpg)(http://uploads.tapatalk-cdn.com/20161212/0ee482326b350388be1fe1d2fe0597eb.jpg)(http://uploads.tapatalk-cdn.com/20161212/1d41d929fdd131aff3eecd05cb459b1c.jpg)(http://uploads.tapatalk-cdn.com/20161212/167bcb1653dac5e8277fd25271e96f2d.jpg)(http://uploads.tapatalk-cdn.com/20161212/01a2d694ea975a1b74ce5048d1e9dcf1.jpg)(http://uploads.tapatalk-cdn.com/20161212/088c63714b57df796e53bbba2a9cb52a.jpg)(http://uploads.tapatalk-cdn.com/20161212/7000332fa4f7f9d4595ee3d19f87d83a.jpg)(http://uploads.tapatalk-cdn.com/20161212/d6abe160d79b6d3f73afd975ab151636.jpg)
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Post by: asantora on December 12, 2016, 07:15:03 pm
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Post by: pbj on December 12, 2016, 07:29:46 pm
Post by: asantora on December 12, 2016, 07:30:29 pm
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Post by: baritonomarchetto on December 13, 2016, 12:41:32 am
Bad tube? Very unlikely.
Post by: asantora on December 13, 2016, 08:27:40 am
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Post by: asantora on December 13, 2016, 08:22:17 pm
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Post by: pbj on December 14, 2016, 12:34:39 am
From looking at your color test picture, I can faintly see red on it which indicates to me that gun is shot.
Post by: baritonomarchetto on December 14, 2016, 01:48:40 am
I am still prone to exclude a bad gun (I do not see any red in the pic, but it could be me...)
Post by: Mike A on December 14, 2016, 06:22:20 am
Post by: big10p on December 14, 2016, 07:48:35 am
Post by: asantora on December 14, 2016, 07:59:43 am
1. There is a tiny hint of red in the test screen.
2. Transistors - Okay, now I understand about testing in circuit. Thanks for teaching me that.
As for grounding out the transistor to test - how does one do that? Is that with the monitor on? If so, I'll go the discharge the anode route and swap spots with another transistor.
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Post by: lilshawn on December 14, 2016, 11:48:33 am
(http://uploads.tapatalk-cdn.com/20161212/1051d8dc0991156a92a140925620405b.jpg)
swap the green and red transistors. if you have red now, it's a bad transistor.
if still no red, (swap back transistors) and swap the red and green video input wires. if "green" lights up in the red area, you are getting red signal but no red output from the tube. tube gun is bad. you can try rejuvenation.
Post by: pbj on December 14, 2016, 12:07:02 pm
These 'unlikely to be a bad tube' people obviously haven't dealt with many 25" monitors.
Post by: asantora on December 14, 2016, 01:14:30 pm
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Post by: asantora on December 14, 2016, 01:16:40 pm
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Post by: lilshawn on December 14, 2016, 01:27:23 pm
Post by: lilshawn on December 14, 2016, 01:33:45 pm
also consider there may be a video amplifier IC (LM1203 or the like) on the main chassis (or a set of discrete transistors) that has a bad red channel on it.
Post by: pbj on December 14, 2016, 01:45:54 pm
You MIGHT get lucky having someone rejuvenate that gun, but it's never going to be as strong as your blue and green. You'd have to turn down their levels until they got close to the red, and then crank the brightness and contrast up.
Post by: asantora on December 14, 2016, 02:08:19 pm
Given that I have SOME red tint. Any hopes of a rejuv? Anyone in NJ/ PA watching this have one? Is it worth me buying the rejuvenator?
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Post by: lilshawn on December 14, 2016, 02:18:01 pm
rejuvenating is really hard on the tube. you basically drive many times more volts into the heater and get them nice and hot, then blast them with high voltage to (hopefully) blow/burn off anything on the gun causing the output to be low.
sometimes you blow out the heater.
sometimes you blow out the gun.
sometimes it works....and if it works, it's a crap shoot how long. could be a minute...a week.. 30 years.
if this monitor is all you got, and all you can get...a rejuvenation might be the only answer. I would call around and see if any place has one you can borrow or will do it for you. it's probably not worth your money to buy one for a one off.
Post by: asantora on December 14, 2016, 03:00:57 pm
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Post by: baritonomarchetto on December 15, 2016, 02:06:19 am
Post by: kardenm on December 22, 2016, 04:47:12 pm
How did you know right from the start?
Is that a really common occurrence for these monitors?
Post by: lilshawn on December 22, 2016, 06:32:00 pm
this was low output.
Post by: pbj on December 22, 2016, 11:06:44 pm
Rejuvenator will improve things a little.
:cheers:
Post by: grantspain on December 23, 2016, 05:08:38 am
Post by: asantora on January 02, 2017, 10:56:18 pm
(http://uploads.tapatalk-cdn.com/20170103/2212b162b1ebb31c8bfa27ff47baf495.jpg)(http://uploads.tapatalk-cdn.com/20170103/a3f5a32bcf476c946802b5e2f7827e27.jpg)(http://uploads.tapatalk-cdn.com/20170103/6ee33ab325238fae4901dc02af657a2b.jpg)(http://uploads.tapatalk-cdn.com/20170103/dc4c83de00f80c97636cf1ca41147aae.jpg)(http://uploads.tapatalk-cdn.com/20170103/bac7068cac3d70437d1198fc24ff63e0.jpg)(http://uploads.tapatalk-cdn.com/20170103/0ec5b03f161737078c450efc56cd8b43.jpg)(http://uploads.tapatalk-cdn.com/20170103/4d2f029272f1e96c1f04351c1a37b742.jpg)
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Post by: pbj on January 02, 2017, 11:38:23 pm
Post by: asantora on January 03, 2017, 07:15:20 am
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Post by: lilshawn on January 03, 2017, 11:56:37 am
I know the CGA to VGA convertor boards (GBS-8220) have an adjustment that needs to be tweaked to have the pic display properly on some machines. (Clamp and ClampSP)
your convertor may have a similar adjustment.
Post by: asantora on January 03, 2017, 09:30:31 pm
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Post by: asantora on January 13, 2017, 10:12:38 pm
Now... the next challenge. I would like to decase the tube tv that I acquired and install it in the arcade cabinet. In order to do so, my understanding is that I will cut the cord on the tv and wire it to the cords coming out of the isolation transformer. This will prevent the mounting ears or other components from being HOT. (By the way, I have yet to figure out where to mount the tv's pcb / chassis, any ideas welcomed). Did I get this right?
Assuming so, I have 3 wires coming out of the isolation transformer that were originally hooked up to the arcade monitor. 2 purple 1 green. I suppose that each purple goes to either (doesn't matter) of the two power cord spliced wires from the tv. But as for the green, which I assume is ground, it was never connected to the arcade monitor. Do I leave it as-is, not connected? Or should this be attached somewhere, like a metal frame for a chassis? A pic of the wires from the isolation transformer attached. Thanks for all of the help. (https://uploads.tapatalk-cdn.com/20170114/8e3a79108e92b5afa939246e76daccaa.jpg)
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Post by: lilshawn on January 15, 2017, 12:22:34 am
whether or not you use the isolation transformer on your TV is up to you. the only reason some monitors needed it is because of the way the older style monitors used a voltage regulator to produce the B+. it needed to not be referenced to neutral becasue neutral is tied to ground.
modern monitors and TV's now use a switch mode power supply that don't need to be isolated.
Post by: asantora on January 15, 2017, 10:20:41 am
One more question as I'm seeing different approaches on various websites. Should I discharge my current arcade monitor and/or the tv before mounting? I'm thinking it's a safety precaution and may not be necessary.
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Post by: pbj on January 15, 2017, 01:23:06 pm
Post by: asantora on January 15, 2017, 04:25:03 pm
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Post by: behrmr on January 16, 2017, 10:29:07 am
Thanks Shawn, I appreciate all of your help. Hopefully I will be able to return the favor soon.
One more question as I'm seeing different approaches on various websites. Should I discharge my current arcade monitor and/or the tv before mounting? I'm thinking it's a safety precaution and may not be necessary.
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If you are going to disassemble the monitor or separate the tube from its chassis you can discharge the tube as a precaution.
Post by: asantora on January 17, 2017, 07:43:18 pm
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Post by: jtb1987 on January 17, 2017, 09:18:09 pm
Messed around with the gonbes video converter a bit and just no luck. So I bought a new power supply, jamma harness, rgb to ntsc converter and made a pseudo supergun for testing and things are looking great.
Now... the next challenge. I would like to decase the tube tv that I acquired and install it in the arcade cabinet. In order to do so, my understanding is that I will cut the cord on the tv and wire it to the cords coming out of the isolation transformer. This will prevent the mounting ears or other components from being HOT. (By the way, I have yet to figure out where to mount the tv's pcb / chassis, any ideas welcomed). Did I get this right?
Assuming so, I have 3 wires coming out of the isolation transformer that were originally hooked up to the arcade monitor. 2 purple 1 green. I suppose that each purple goes to either (doesn't matter) of the two power cord spliced wires from the tv. But as for the green, which I assume is ground, it was never connected to the arcade monitor. Do I leave it as-is, not connected? Or should this be attached somewhere, like a metal frame for a chassis? A pic of the wires from the isolation transformer attached. Thanks for all of the help. (https://uploads.tapatalk-cdn.com/20170114/8e3a79108e92b5afa939246e76daccaa.jpg)
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asantora, can you clarify specifically what was able to solve your problem? I think I have the same problem as you discuss in your original post but have no idea where to start. See attached
Post by: asantora on January 17, 2017, 10:39:48 pm
Before I go on, I want to say that this isn't necessarily the same issue that you're having. If I were you, I would first check your video cable wire from the jamma harness to the monitor to make sure that it has continuity. I also learned to check and flood the transistor for each of the 3 (rgb) transistors. After I did not see much red, I was told / learned that my tube was caput.
So, my solution was to buy an old tv and rbg to tv converter and wire that up (still a work in progress).
Hope this helps
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Post by: asantora on January 17, 2017, 10:42:48 pm
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Post by: jtb1987 on January 17, 2017, 11:09:48 pm
Thank you for the reply - would you mind going even further in elaborating on the options you gave to troubleshoot further?
I also just realized that if I hold the grey cord differently that goes from the jamma to the monitor, I can get the color to work correctly....does this indicate that there is something wrong with the grey cord, the jamma connection, or the neckboard connection? When i hokd the grey cord straight up, it seems to fix the color. If it bends slightly at the monitor connection, the color goes to all blue. What would I need to do to holistically solve the this issue? Would just replacing the grey cord fix it and if so what is it called and where do you buy them?
See images of grey cord and how I got red to come back by holding it differently...
Post by: buttersoft on January 17, 2017, 11:33:33 pm
"The Jamma to the Monitor" meaning the Jamma edge of the Tekken PCB to the first part of the Chassis (PCB that drives the monitor)? (The chassis is the big board, the neckboard being the little PCB attached to the pointy back end of the CRT itself, farthest from the flat side where the picture shows.)
Check the solder joints under and around the connectors of that grey cable at both ends. Even if they look ok you could reflow them. If it's not that, see if you can get a needle or pin into the ends of the connectors, to narrow the holes, so to speak, and help them hit the pins. If they still won't grip, you might have to redo the cable.
EDIT: looking at the pics more closely, there's a bit of room there to wiggle those wire individually, or at least watch what pulls on what when you move the cable.
Post by: asantora on January 18, 2017, 07:44:52 pm
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Post by: lilshawn on January 18, 2017, 08:04:17 pm
if you look at the backside i'll bet you can see it.
Post by: jtb1987 on January 18, 2017, 09:43:16 pm
Thankfully it sounds like a correctable problem.
First off, what is the name of the grey cord? Is there an online parts shop where I could buy a new one?
With that said, it sounds like cord isn't really the problem - it's the connectivity between the cord and the connection to the monitor chassis. I apologize but I'm still a little bit confused on how I would go about fixing it...do I need to re-solder the connection? I wouldn't solder the cord to the board as its meant to disconnect so I'm just unclear exactly the next steps...
Thanks everyone for being so helpful.
Post by: pbj on January 19, 2017, 09:19:42 am
Take out the board.
Reheat the solder on the board where the grey cable plugs in.
Post by: astroroxy on June 11, 2019, 03:57:02 am
This is the first one that I have been able to see exactly what it is.
Post by: lilshawn on June 11, 2019, 11:14:49 pm
Post by: astroroxy on June 12, 2019, 02:22:45 pm
are you lost? there are literally thousands of pictures of the WG K7400 / K7500 monitor chassis out there. I find it hard to believe this is the first picture you've seen of it.So this is actually a sharp image.
From what I can tell it's a close clone to the K7100, definitely not 7400/7500
(I'm talking about the pics from the original poster.)
Post by: lilshawn on June 12, 2019, 02:51:51 pm
Post by: astroroxy on June 12, 2019, 06:16:27 pm
oh you mean way way back in the beforefor times, not the last pics posted. (http://forum.arcadecontrols.com/index.php/topic,152601.msg1602437.html#msg1602437)Yep, the original pics
Post by: lilshawn on June 12, 2019, 08:13:15 pm
http://www.homearcade.org/BBBB/monitor78.html