Basic monitor information - how to ask good questions. Read this first

Ian - Thanks!

I am having some monitor issues at the moment and this has been extremely helpful.

Could I suggest pictures with arrows pointing to all the relevant parts?

I get the general concept but pictures would take it from conceptual to practical for me...

I have learned a lot in a short period of time - reading here and you tube for some great vidoe how tos'....

Thanks again for this!

Chris
 
DON'T connect a monitor directly to a wall socket! Most game monitors are "hot chassis", and as such require an isolation transformer. Plugging such a monitor directly into a household wall socket will fry stuff. This especially includes Nintendo monitors. They have a standard looking wall plug on the cord, but that's meant only for the 100v isolated socket in the bottom of the game.

sigh - found this 1 day too late. good info though - thanks! might have something to add on the 20 EZV's and K4900's when i get some time (after fixing this last fiasco).
 
Great post Ian, you have nicely summed up what i have spent thousands of hours doing by phone or pm, and after all that there are some people that just don't get it. if you' re one of these people, i would strongly suggest sending your monitor chassis off to someone that knows what they're doing.

Randy Fromms flowcharts should be considered very basic info at this stage of a monitors life. His info was useful 10-15 years ago but these old relics have way more issues than his flowcharts can even begin to cover.
 
I didn't see any links posted, and I've collected some from past KLOV posts that I worry I won't be able to find again:

Wikipedia entry for Cathode Ray Tube
Ultimarc's Monitor FAQ (newbie friendly)
Sam's Monitor FAQ at repairfaq.org (comprehensive!)
CRT tube reference chart (starts on page 6)
CRT Cross Reference Chart
Donor TVs for Arcade Monitor Picture Tubes / Arcade Monitor Reference
So you wanna swap a tube...
Monitor Tube Swap


I also think this sticky needs sections for "Tube Swapping" and "Using a CRT Analyzer/Restorer". The info in posts from Ken Layton and others is golden, but is sometimes hard to find in a thread search.
 
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"Why do I need to post pics of my monitor problem?"

Because your description of the problem may not be as accurate as you think it is, and my monitor is not broken yours is.
 
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Resolution questions

I was wondering if there is anyway to quickly tell what resolution the chassis is and not know what model the chassis is?
To go along with that what is the difference between the resolutions and how can you tell what game needs what resolution monitor to work correctly. Sorry if this makes no sense make any changes that are necessary. As always thanks for the help guys.
 
1) An explanation of the differences between resolutions:

http://www.arcade-museum.com/monitor.html

2) How do you determine the resolution requirement of your game? Most will be listed in the description on the KLOV page for that game, although a few are incorrect (but being corrected as we figure those out):

KLOVClip.jpg


Sometimes you can use the manual to figure it out, if you can find a copy online.

3) As for determining which resolution a monitor is - first you have to identify the chassis model if you can:

http://therealbobroberts.net/monitor.html
http://www.jomac.net.au/mon.htm

Once you know the model, it's pretty easy to determine it's resolution, although some models operate under more than one resolution.

4) Your best bet is to try the links above first to figure it out. If you can't or aren't sure, take pics and/or come here and ask questions...
 
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This is awesome. Just ran into this problem with a G07 I replaced the width coil on as it was cracked in half when I got it. I have another G07 that I think the B+ is dead as it fires on for a split second and then dies immediately without blowing any fuses. At least now I know how to tune the new B+ once I replace it.


Probably does, I've seen several Centipede's with G07's.

To adjust the B+ on a G07, connect the black lead to the montior's frame. Red lead goes to the end of the large ceramic resistor closest to the picture tube. The adjustment pot is laying flat on the chassis, behind the vhold pot. You're looking for 120v.

If it still won't fit on the screen after doing that, you may have to adjust the width coil. The width coil on a G07 is the white plastic tower in toward the front of the chassis, in front of the flyback. The width coil on a G07 is a notorious weak point. Be VERY careful adjusting it, as it's very brittle. If it breaks, you'll have to replace it. Turn a width coil ONLY with a PLASTIC tool. Never metal. You used to be able to get plastic adjustment tools at Radio Shack, but I don't know if they still carry them.

A width coil is essentially a variable inductor. When you adjust it, you're actually moving a ferrite slug up and down in a threaded plastic form, moving it in and out of the magnetic field of the coil. The problem is that this ferrite is brittle, a metal tool will break it. Also, the plastic form is very brittle from age and heat. Start slowly, try to work the slug back and forth a bit to get it freed up. Never adjust a coil to it's extremes, it shouldn't take that much tweaking to get it in line.



A note on vertical vs. horizontal monitors:

Some games (like Centipede, Ms. Pac, etc) use a vertically mounted monitor. Other games (Defender, Popeye, Berzerk, etc.), use horizontally mounted monitors. The difference between them is... nothing. The monitor electronics are exactly the same. They're just mounted sideways for vertical operation. When referring to monitor adjustments, the controls always refer to standard horizontal orientation (like a television set). So, if in Centipede, your high score and stuff is off the screen, then to adjust it, you need to adjust the width of the picture, not the height.

Some monitors have a metal frame that holds the tube vertically, but again, these are no different than a horizontal monitor - the controls on the chassis still refer to dimensions in terms of a horizontal orientation. The chassis in a vertical monitor is identical to the same chassis used in a horizontal one. Interestingly enough, most vertical games actually just use a standard horizontal shelf-mount monitor, mounted sideways, rather than a monitor with a vertical frame.

-Ian
 
could have used this thread about 14 years ago when i fried not 1 or 2 but 3 yes 3 perfectly good monitors by bypassing the iso. I learned the had and expensive way. I quickly did all the research i could and asked any one who would listen. I even worked free for the dealer in our town just for tidbits of info. Also i had no internet then my how times have canged.
 
Im reading how to do a cap kit, but a little unclear on where the caps are located? Are they on the monitor baord below the monitor or the little baord just behind/posterior to the glass tube/bulb? And Im assuming I will be taken out the baord to recap.
 
they will almost all be on the chassis. Usually there is one or two on the neck board as well. Yes, you will need to pull the chassis from the machine since you will need to solder on the underside of the board. I usually just pull the chassis, but on some monitors, the sanyos in Nintendo cabs especially for me, it is easier to pull the whole monitor for easier chassis removal.

Take pictures of everything before you touch it. That will help you when you put it all back together. On your first (few) capkits, remove and replace the caps one at a time. Look at the polarity of the cap before you remove it, then install the new one the same way. The polarity is shown on the board, but sometimes they are wrong, so it is best to make sure by looking at what was on there.


I remember seeing a post that showed the pot settings to start out with after a capkit (for the k7000 I think). Does anyone have a link to that? I think that would be good to add to this thread. I remember getting way closer to proper adjustment just blindly following that than I could get by watching the changes on the screen. Sometimes they are way out after the caps are replaced.
 
Deflection basics:

What is deflection? Well, first, a little bit about the basics of CRT displays. The inside face of the picture tube is coated with phosphors in three colors, already discussed earlier when I talked about screen burn. Slightly behind the face of the tube is a metal grille, known as the shadow mask. It looks like a cheese grater - staggered tiny holes. You can't see it from the outside of the tube (you'd have to disassemble it to see it, and by disassemble, I mean "break with a hammer"), but trust me, it's there. Then, at the neck of the tube, is the electron gun assembly. This contains three separate electron guns, that are driven by the monitor electronics. The tube is filled with a vacuum (that is to say, not filled at all...).

So, the monitor electronics drive the electron guns to emit pulsed streams of electrons. There are three guns, each aligned with a particular set of colored phosphor dots. Electrons travel very nicely in a vacuum, and left to their own devices, leave the guns and travel directly straight ahead. This is great if you just want a tiny dot of light in exactly one place, but we'd much rather have them be able to light up the whole screen with a picture. That's where the deflection circuits come in. On the neck of the tube is a rather largeish coil of copper wires. This is the deflection coil, more commonly known as the yoke. The yoke actually contains two independent sets of coils - one for horizontal, and one for vertical. If you were to take the yoke apart, you could see the separation.

Now, electrons in a vacuum are affected by a magnetic field. They're deflected by it. So, by applying a signal to the separate coils of the yoke, the yoke creates magnetic fields that bend the stream of electrons and change the area of the face of the tube that they will hit. In a typical raster monitor, this beam of electrons deflected by the yoke and is scanned across the tube, from top to bottom, left to right, painting a picture as it goes. Imagine it like a REALLY fast printer. The electron beam is only touching one tiny point of the tube at a time, but since the phosphors stay lit for a while, and our eyes themselves have a certain persistence to them too, we see a stable, unmoving image. When in reality, only a tiny fraction of the screen is being written to at a time. This is why, when you record a video of a CRT display with a camera, you sometimes see this band of darkness waving through it. That's because the camera can capture things faster than the eye can, and it's catching the electron beam.

When the beam gets to the bottom of the screen, it's shut off, and the magnetic field is changed to bend it back up to the top. This takes a very tiny amount of time, but it's known as the "blanking interval". But, the beam isn't truly turned off all the way, it's still there, just with not enough energy to light anything up. But when you turn the SCREEN control on the flyback all the way up, it causes that "blanked" beam to be visible, resulting in the angled retrace lines on the screen.


What about vector monitors? Those are different, right?

Yes. They are. In a raster monitor, the deflection electronics are fixed at a particular pattern and frequency. They scan the tube exactly the same way, all the time, and synced up to the game board's signal via the sync line(s). Vector monitors, on the other hand, have no sync line. Instead, the deflection circuits are directly controlled by the game board. Vector games can manually bend that beam of electrons anywhere on the screen at any time, turn the beam on, then bend it someplace else, and shut it off again - allowing a perfectly straight line to be drawn from one point to another. It's the difference between coloring in squares on graph paper and drawing free-form. Vector monitors are thus different from raster monitors because they have these deflection amplifiers with direct inputs.


And how does convergence fit into all this?

Convergence is the alignment necessary to get the red, green and blue "beams" to converge at the same spot on the screen. Those three beams are separate, and need to be aligned so they work together. First adjustment is actually purity. Purity is the ability for a particular beam to ONLY hit it's proper color, and not "miss" and hit the wrong colored phosphors. Then, the convergence must be set up to align the beams with each other. Convergence is achieved by the way of tiny little magnets, mounted on movable rings, right between the electron gun and the deflection yoke. Basically, to "prebend" the beams of electrons, to get them lined up, before they're bent all together to scan the face of the tube. These tiny magnets can affect (mostly) only the one particular color since they're right next to the guns. But getting them aligned is a royal pain, and is outside the scope of this guide.


You said something about a shadow mask?

Yes. And I almost forgot. The shadow mask is basically a stencil. A piece of metal designed to ensure that the electron beams don't "spill over" onto the wrong dots on the screen, and only hit one at a time. This shadow mask sometimes gets slightly magnetized, however, and it bends the electron beams as they pass through, causing them to miss their mark! This causes a psychedelic colored picture. When this happens, the tube must be "degaussed", which is just a fancy way of saying "demagnetized". A picture tube is very sensitive to magnetic fields, including the Earth's magnetic field. Usually, when you move a monitor, it must be degaussed. Because this degaussing is so important, all color monitors and televisions have built-in degaussing coils. That's the fat (usually black, sometimes grey) cable that snakes around the back of the tube near the face. It looks like it was wrapped in lots of tape. It's another magnetic coil - and it gets fired for a second or so every time the monitor is turned on from being cold. That's the "thooom" sound that some monitors make on powerup. Sometimes, the shadow mask gets too magnetized for the weak little coil in the monitor to clear it up. Multiple cold powerup cycles can help it, but other times you need to degauss it manually with a handheld degaussing coil. Also, it IS possible for a strong magnetic field to permanently magnetize or even bend the shadow mask. Similarly, a tube that was dropped hard enough can bend or dislodge the mask. If this happens, there is no repair short of replacing the picture tube.


-Ian

Good Thread, Ian and Others

Do you think the Questions are getting better from techs and DIY's alike?
I think So.


I hope theres alot of online research going on..
Because theres alot more to Learn!!!


Heres some picture of inside the CRT's
to add to the thread.
 

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Start a new thread for your issue, and include a picture of the screen so we can see what you are talking about....
 
Fantastic thread, many thanks to all the contributors :) I have read it all once and will read it again before I try any tricky work.

More pictures with detailed parts descriptions would be great.

I have an Asteroids Vertical Cab with a G05-802, I have done a couple of minor repairs to the main PCB but no monitor work as yet, soon going to replace my HV Diode and a few caps to see if I can get my near perfect picture to rock solid perfection :)
(part of me says if it ain't broke don't #$%^ with it, but I can't help it)

Seeing as I have a wife and kids, I'm still a bit wary about the safety issues, so would like to clear a couple of things up if some could be kind enough to help.

If I have the monitor on is it possible to get a shock if I accidentally touch the back of the screen?

What about the flyback? that's insulated isn't it? from what I have read the only real dangers are pulling the rubber cap off the monitor or working on parts inside the HV cage.

I have done some picture adjustments and obviously the monitor needs to be on, with the back open while I fiddle around inside with the PCB quite close to the monitor and wiring. Just would like to know how much of a risk I'm taking while doing this, nice to know in retrospect :)
 
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