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

EVB summed it up pretty well there. Though the OP made that post 6 or so years ago, it's still worth re-iterating that LCDs are bad. Another issue that one has to keep in mind when using an LCD is the lag. Unless you are spending thousands of dollars on special equipment, or have an expensive transcoder the video signal runs through, you will have some lag present that will never be present on a CRT.

For some of the classic games, this extra couple of frames of lag between when you press a button and when action takes place can be VERY noticeable. You might not notice lag on a modern game that is designed from the get-go to use digital signal transmission, but on an old game generating analog video, it's going to be there.

Therefore, the use of an LCD does introduce changes to the gameplay itself.
 
Is any of this useful information to anyone, or is it just too long and nobody is going to bother to read it?

-Ian

Just thought I'd mention that 10 years later, this information is like gold for someone just getting into monitor repair. Reading and re-reading before my first discharge and cap kit.
Thanks!!!
 
One more question if someone doesn't mind. What is the difference between B&K Socket and Sencore Socket

Example:

*edit* Guess I found my own answer. They're adapters for different brands of tube rejuvenators? Which one is more important to reference when tube swapping?
 
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it all depends on what tube you have, if the tube has a different pin out then you have to have the correct adapter.

a CR-23 is the same on any tube with that pin out.
same with any other adapter.

some tubes are a CR-23 but have more or less ground pins, so some CR-23 tubes have between 10-12 pins
the adapter will work on all of them.

no mixing and matching in this case between other adapters.
just because the socket fits on a tube does not mean the pin out is correct.

you can/will blow up your rejuvinator and possibly the tube when using the wrong adapter.

ALWAYS check the tube # to verify what adapter you need if it is not a common known chassis type that is on the tube.

also there is no cross reference guide from the Sencore, Heathkit or B&K adapters.
they all have different ways to tell you what adapter to use for their specific machine model.

Peace
Buffett
 
Noob question. I see crt socket types referenced as CR-23 or CR-31 etc etc. Is there a list somewhere that tells me all the types and the pin counts? Like what is this one? (k4903 off of a moon patrol)
thanks



User Dezbaz here put this together:

CR-XX_Conns&No_Dez.jpg


From this thread:
 
I've become the new owner of a B&W monitor this morning for a Space Invaders cocktail I'll be getting in the next month or 2. So much of this info here has been helpful in understanding monitors of different types. Thank you!
 
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
Thank you Ian for such a great explanation of monitors! I love it! I picture the Shadow Mask to be similar to that of the screen in my microwave door/window. Anyways, thank you for your time and help. I found this a fascinating read and very enlightening (even though you posted this 15 years ago).
 
Thank you Ian for such a great explanation of monitors! I love it! I picture the Shadow Mask to be similar to that of the screen in my microwave door/window. Anyways, thank you for your time and help. I found this a fascinating read and very enlightening (even though you posted this 15 years ago).


If you like that, you'll love this:


(And the page it comes from, which has even more: )

 
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