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Offline TRS-90

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Component video questions
« on: April 26, 2016, 05:10:51 pm »
I don't know if this is the right place for this, so if it is the wrong place forgive me.

Component video has a sync signal in one of the cables (sometimes the green one in case of the Playstation 2) and I was wondering if it was possible to separate the sync (or horizontal/vertical drive) signal from the color signal in whatever wire contains it.
I am trying to drive a CRT from a macintosh by reverse engineering the analog board but I need a way to drive the coils that make the electron beam move.
I can use the RGB signal from the cables I just need to make the image work instead of just being a dot on the screen.

I am a beginner in the electronics, I just have done some research on CRT technology but have found very little.
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Offline stmdude

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Re: Component video questions
« Reply #1 on: April 26, 2016, 05:22:14 pm »
Have a look at the LM1881.  It's a "Video Sync Separator", so it might fit the bill. :)
 

Offline TRS-90

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Re: Component video questions
« Reply #2 on: April 26, 2016, 05:40:36 pm »
Thanks!  This just might solve my problem!

If it can work with a component signal instead of only composite then I can make it work.
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Offline stmdude

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Re: Component video questions
« Reply #3 on: April 26, 2016, 05:46:12 pm »
Should work fine on component as well, it's the same timing.  Just make sure to put it on the signal that actually has the sync.. :)
 

Offline TRS-90

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Re: Component video questions
« Reply #4 on: April 26, 2016, 05:55:47 pm »
Just got to make sure that I'm able to hook it up to the deflection coils.
I may need a transformer to boost the sync signal to make it drive the coils.

But the coil connector has 4 wires but this chip has only 2 sync related outputs.

I don't know how much of a problem that will be, but it should help anyway.
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Offline N2IXK

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Re: Component video questions
« Reply #5 on: April 26, 2016, 06:08:56 pm »
If you want to drive the coils in a deflection yoke,  you need a lot more than a "transformer".  You need power amplifier stages designed to work with the particular deflection yoke in question. Like the ones already in place in the Mac CRT monitor....

You also will need circuitry to shape the pulses from the LM1881 into proper sawtooth waveforms to get anything resembling proper linearity on the screen.

You should really study the monitor schematic, and see how the original design dealt with the sync signals, separated them into H and V sync, and applied the sync signals to the H and V sweep oscillator stages.

The majority of CRT monitors derive various operating voltages (including CRT high voltage) from the horizontal sweep stages, so forcing the horizontal sweep to work at a radically different frequency than designed for can upset these voltages, and perhaps even damage the circuitry. In short, what you are trying to do is nowhere near as trivial as you seem to think, especially without a good grasp of the workings of CRT displays.
"My favorite programming language is...SOLDER!"--Robert A. Pease
 
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Offline TRS-90

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Re: Component video questions
« Reply #6 on: April 26, 2016, 06:18:26 pm »
Ah.
I never really thought it was easy seeing as no one has ever done this before from what I know.
I found a hookup for the color but the issue with the project is getting from a dot on the screen to a working image.
I just need a way to make it work and also I can't seem to find any decent info on the way sync was handled(I'm not the greatest at understanding analog technology).
I don't know if this helps but the CRT in question is a 14" Sony Trinitron (but only 13" are visible or so I hear) from 1994/95.

Any information I can find helps.

 
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Offline TRS-90

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Re: Component video questions
« Reply #7 on: April 26, 2016, 06:30:54 pm »
As a side note I looked up "Square wave to sawtooth converters" and did find some.
So that is one problem solved (probably not because I'm never THAT lucky).
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Offline N2IXK

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Re: Component video questions
« Reply #8 on: April 26, 2016, 06:33:22 pm »
First thing to do is to get a schematic/service manual for the monitor you are working with.  Trying to reverse engineer or modify the circuitry without one is NOT a good idea, particularly if you aren't familiar with the basics of how analog video and CRT displays work.

BTW, most CRT monitors use a "hot chassis" type power supply system, which can present a serious shock hazard when attempting to add new I/O connections like you are seeking to do.  Again, a schematic is needed here to figure out the boundaries of the hot and isolated portions of the circuitry.
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Offline Richard Crowley

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Re: Component video questions
« Reply #9 on: April 26, 2016, 06:39:17 pm »
What exactly does "a CRT from a macintosh" mean?
Do you mean "a CRT monitor with RGB video inputs", or do you mean "a raw tube with the yoke and no supporting electronics"?
If it is the latter, I'm sorry to report that you have an almost impossible task.

Creating the precise horizontal and vertical sweep waveforms, and all the high (and VERY high) voltages for the CRT are a very specialized form of circuit design. Not to mention all the very specialized and arcane circuits needed to focus and align the three electron beams to the Red, Green, and Blue phosphors on the face of the tube.
Creating all that from scratch, or even adapting the chassis from some other color CRT, is an advanced project that significantly eclipses whatever other project you are attempting.

If you really want a color CRT display, you need to start from a complete, functional chassis with the tube, the yoke, and all the associated electronic circuits.
 

Offline TRS-90

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Re: Component video questions
« Reply #10 on: April 26, 2016, 06:48:08 pm »
What I mean is that it is a standard Sony trinitron tube just driven by apple designed circuitry.
There is some supporting circuitry inside (if a neck board counts).
The neck board has RGBHV connectors on it but the sync information and color is generated by the motherboard and, I assume, is amplified by the chassis
So while I may be able to get a dot on the screen using component connectors, that's all it will be, a dot, while that is a leap in my book, it isn't a stable image.

So what I'm looking for is a way to get the electron beam to move left, right, up and down as per the video signal being put into the CRT.

I'm trying to hook up a video game console to the tube and use the original case and tube, that is my goal.
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Offline TRS-90

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Re: Component video questions
« Reply #11 on: April 26, 2016, 07:02:52 pm »
A mild correction on my previous statement:

I do have an analog board but I can't just solder a video input and call it a day unfortunately.

I did hear that some of these boards (even the ones put into macintosh computers) had an RF section on them but I can't find it on my board because I don't know what I'm looking for.

End of correction.
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Offline stmdude

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Re: Component video questions
« Reply #12 on: April 26, 2016, 07:19:41 pm »
For other people wondering what's _actually_ inside this thing, here's the "Service Source" documentation:
http://tim.id.au/laptops/apple/legacy/performa_500_series.pdf

I don't know much about CRTs (except that they'll more or less kill you if you don't know what you're doing), but I do know that you're going to need to use that analog-board..

To figure out _how_ to use the analog-board, you're going to need an oscilloscope (unless you can find the schematics) to probe the signals between the main-board and the analog-board, and figure out which signals are where, and at what timings and levels.

Once you know that, you'll need to get whatever game-console you wanted to put in there, and see if you can extract those exact signals from it somehow.

Unfortunately, most likely, you won't be able to, as pretty much all game-consoles are meant to drive a TV, whilst what's in the Performa is a monitor. The monitor in this case has a resolution of 640x480, meaning, it's not one of the standard TV signals (PAL/NTSC), nor is it a multiple thereof.
As the trinitrons have an aperture grille (does all CRTs have them?), even if you somehow manage to drive it with different timing (NTSC for example), the picture would be "blurry", as the pixels won't line up with the grille.

 

Offline TRS-90

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Re: Component video questions
« Reply #13 on: April 26, 2016, 07:36:31 pm »
I can't afford an oscilloscope unfortunately and nor can I find the schematics but from what I understand a CRT of the exact same size was used in a Sony TV.
It was a 14" TV.
The monitor uses a 66.67Khz /Mhz?/Hz? signal from what the manual said (that or it was one of the shadowmask CRTs used in other computers).
The reason I thought I could use a transformer to drive the coils is because of the "turn a TV into an oscilloscope" project that has been around for a while.
They use a somewhat similar method by hooking up the left and right audio channels to the coils through an amp or some sort of signal booster(it's been done on some pretty big televisions too) to make the line on the screen into a waveform from the signal source.
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Offline Richard Crowley

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Re: Component video questions
« Reply #14 on: April 26, 2016, 07:42:34 pm »
If all you have is the tube and the yoke (and color alignment adjustments etc.) then you have less than half of the actual display.  I am afraid you are dramatically underestimating what it takes to operate that part of a display you have.  IMHO, it is simply not practical to try to revive what you have unless you have the whole circuit that it came with.  As you learn more about what it takes to drive a color CRT display, you will realize what a monumental challenge you are facing.  With ~50 years of experience behind me (including color CRT displays) I wouldn't even dream of attempting such a thing. Sorry.  If you really want a color CRT display, then at least start with the WHOLE THING instead of less than half of what you need.

Even if you could get the vertical and horizontal sweep to operate, you really don't even want to know what a horror it is to try to get the colors aligned so that the picture doesn't look like a 1960s hippie drug-induced dream image of rainbow patterns.
« Last Edit: April 26, 2016, 07:45:36 pm by Richard Crowley »
 
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Offline TRS-90

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Re: Component video questions
« Reply #15 on: April 26, 2016, 07:50:53 pm »
I actually have the whole thing.
But a lot of it is by apple so getting the schematic is near impossible.

The adjustments are near where I can attach the component inputs.

The coils have wires going to the board so I just need a signal booster and the signal information.

I just need the make the signals come from an external source instead of the motherboard.
But the problem is that is has no TV type circuitry, if it did I could just solder an input to it and call it a day.

A blurry image on the screen would make me more than happy.
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Offline TRS-90

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Re: Component video questions
« Reply #16 on: April 26, 2016, 07:54:59 pm »
Who know maybe I could jerry rig the motherboard and use that because it drive a lot of the video :-//.

I wish there was a way to find the apple schematic but they probably have it locked in a mission impossible level vault somewhere in cupertino california.
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Online helius

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Re: Component video questions
« Reply #17 on: April 26, 2016, 08:02:25 pm »
The neck board does not carry H or V sync signals, those are applied to the flyback and HOT section which drive the deflection yoke. The neck board receives the R, G, B, signals and may also have "drive", "screen", or "blank" signals, if it contains video amps, which is common. The grid electrodes (high voltages) and the filament circuit are also connected through it.

Component inputs could mean RGBHV, but with household equipment it more often means YsUV (YPbPr). Those cannot drive a CRT without being converted to the RGB color space.
 

Online helius

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Re: Component video questions
« Reply #18 on: April 26, 2016, 08:19:16 pm »
I explained in your other thread that the Mac main board does not have any monitor driver circuits, those are all on the other board. If you compare photos of the LC 575 board and something without a CRT like the LC 475 board, they have the same (5V) components. CRT drive circuitry is at high voltages, and you can tell just from the PCB material that it is completely different.
What kind of inputs does a computer monitor receive from a computer? The only ones that matter are RGB and Horizontal and Vertical sync. Nothing composite and nothing with YUV components. All of those signals are present at the edge of the "analog" board, and my bet would be that they are at normal signal levels (1 Vp-p for the color channels and + or - 5V for sync). Those are the only things you should connect to.
 

Offline TRS-90

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Re: Component video questions
« Reply #19 on: April 26, 2016, 08:30:54 pm »
What I meant in my other thread was that the signals are generated by the motherboard but are amplified by the analog board(at least that is what I heard, you are probably correct, I am fairly new to the world of video circuitry).

Does anyone know what pins on the connector harness has the video (R, G, B, H sync and V sync) and power supply activation.
That would probably solve most of my issues.
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Offline TRS-90

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Re: Component video questions
« Reply #20 on: April 26, 2016, 08:42:13 pm »
Would something like SCART work?  :-+ or  :--
It has R, G, and B, sync pins and so on.

I am completely unfamiliar with SCART as I have never used it, please feel free to correct me on this one.

There is a SCART adapter for to playstation 2 so that is not a problem.

Or is SCART the worst possible way to go about this.

Also what does SCART stand for?
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Offline Richard Crowley

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Re: Component video questions
« Reply #21 on: April 26, 2016, 09:06:28 pm »
Here is a typical last-generation, highly-integrated color CRT circuit.
You have the block in the center-right.
What you are missing is the REMAINDER of the circuit.
Including the deflection circuits and the EHV circuit in the block at the lower right.
These are very tricky circuits even to repair in a commercial product.
Nobody in 2016 would attempt to reproduce a circuit like that from scratch.

 

Offline TRS-90

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Re: Component video questions
« Reply #22 on: April 26, 2016, 09:12:09 pm »
WOW.
Thanks for that.
Now I might be able to decipher some of this thing.

I can read circuit diagrams pretty well if I know the components.

I'll see if I can work this out.
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Offline chris_leyson

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Re: Component video questions
« Reply #23 on: April 26, 2016, 09:50:03 pm »
Quote
1960s hippie drug-induced dream image of rainbow patterns.
you get interesting interference patterns when you bend the shadow mask out of shape, somehow it got dropped on its front, can't remember how it happened, wasn't there at the time. It buckled into a different shape, I'm looking at cool diffration patterns and everybody else looking a busted TV, they didn't think it was cool :-DD


 

Offline Richard Crowley

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Re: Component video questions
« Reply #24 on: April 26, 2016, 10:59:09 pm »
WOW.
Thanks for that.
Now I might be able to decipher some of this thing.

I can read circuit diagrams pretty well if I know the components.

I'll see if I can work this out.

REMEMBER:

This is NOT the circuit for your device.  It represents the complexity of even the most simple color CRT monitor system.  Your unidentified device may have more or less circuit than the one in the diagram on the board(s) around the yoke.  Can you find an OEM identification on the board somewhere?  I doubt that Apple actually made their own CRT displays. They probably bought them as sub-assemblies from an OEM.  Just as today they don't make their own LCD screens, they buy them from an OEM.

CRTs use LETHAL voltages that will KILL YOU DEAD. Even experienced technicians and engineers are at risk.  This is NOT the kind of circuit to be fooling around with if you are "a beginner in the electronics".  You are way out of your depth.   :palm:

The inner and outer conductive coating of the CRT display tube form a VERY POWERFUL storage capacitor.  Even hours after being powered down and completely disconnected, the charge stored in a CRT is potentially LETHAL.
 

Offline TRS-90

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Re: Component video questions
« Reply #25 on: April 26, 2016, 11:10:54 pm »
Well apple did not make the tube Sony did but the board that drives it they at least designed as it is labeled on the board (c) Apple Computer 1994 (or something similar).

Also the thanks was for the ability to see how to tuner and driver and such worked to possibly build one (probably out of my league I know but I might have someone who can help me with this).

What I really need right now is a pinout diagram of the harness that the motherboard plugs into,  if I have that then I may not need to almost kill myself(I have actually been inside the display housing even while the tube was running).

People have also rigged VGA to one of these displays but never seem to say how they did it.

SCART might work for this project but I can't confirm that.
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Offline Richard Crowley

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Re: Component video questions
« Reply #26 on: April 27, 2016, 12:45:49 am »
VGA and SCART are both just alternate names (and pinouts) for RGB.  But that is the very least of your problem.

But you are missing 60-80% of the critical circuits it takes to get RGB/VGA/SCART/whatever into the signals it takes to actually drive color CRT.  Note that the horizontal and vertical sweeps are not just amplified sawtooth waves, they actually use the inductance of the deflection yoke windings as part of the inductance in a tuned L/C circuit.

Even if you knew the pinout of the yoke board, you would still have <5% of the information you need.  Especially now that CRT displays are long-dead, it seems even less likely that you will be able to find any repair information. Nobody wastes their time fixing these things anymore. Except...  Perhaps your best shot is a computer museum specializing in Apple products.  Often museums have volunteers who work there who were involved with the same products back when they were working for Apple.

I would put my efforts into acquiring a fully functional color CRT display.  Since most people are (or have) replaced their old CRT displays with modern LED/LCD/plasma, etc you should be able to find fully functional color CRT displays, (even broadcast-quality monitors that cost as much as your car) free for the hauling away.  However it is so late in the game that the supply of CRT displays is probably on the tail-end of complete extinction. 

I have a broadcast-quality 13-inch Sony color monitor that I will give you for free if you live near my city (Portland, Oregon)  Else I will take it to the recyclers.
« Last Edit: April 27, 2016, 12:49:32 am by Richard Crowley »
 

Offline TRS-90

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Re: Component video questions
« Reply #27 on: April 27, 2016, 12:55:55 am »
Well that's not good.

The motherboard harness has the video connectors on it (as an edge connector) so if I find the pinout of it I could use that instead of using a bunch of the CRT stuff.

The main reason I wanted to do this was to not waste a perfectly good display on a machine I paid for.

If I'm missing a ton of the critical circuits (which I most likely am but I don't know, also the machine is new I haven't lost any parts) then is there a way to find out how apple did it?

If I get a picture or few of the insides I'll post it/them here (while being careful of the high voltages).
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Offline Richard Crowley

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Re: Component video questions
« Reply #28 on: April 27, 2016, 01:15:00 am »
But you don't have "a perfectly good display".  Far from it.  You have a few random pieces of "a perfectly good display".  And you may spend the rest of your life trying to find the missing pieces.  IMHO you have already spent more time on it than it is worth.
 

Offline TRS-90

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Re: Component video questions
« Reply #29 on: April 27, 2016, 01:39:42 am »
IMAGE TEST
[0426162004.jpg][All in Computer\LGL39C\Internal storage\DCIM\Camera]
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Offline Richard Crowley

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Re: Component video questions
« Reply #30 on: April 27, 2016, 01:50:40 am »
Well, that didn't work.
The photo file(s) must be posted in a public place where we can see them.
Then you can include a URL reference to wherever the photo(s) are.
 

Offline TRS-90

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Re: Component video questions
« Reply #31 on: April 27, 2016, 02:01:38 am »
Here (hopefully) is an attached image file.
If this works then I will post some more so you can see what I have or don't have.
This one being the CRT running.

I DID NOT PRODUCE THE VIDEO SIGNAL IT IS FROM THE MOTHERBOARD THAT PLUGS INTO AN EDGE CONNECTOR.

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Offline TRS-90

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Re: Component video questions
« Reply #32 on: April 27, 2016, 02:09:53 am »
WOW that actually worked.

Also when looking around the CRT driver board I saw some chips that maybe someone could identify.
If I wrote the correct numbers down.
Phillips: TDA 7052A (there were about 2 or 3 on the board)

Motorola: 337-0080 or LEC9432 (only 1 on the board)

(couldn't identify the logo but it looks like an H with a weird S through it): TDA 4605-2 (2 of these on the board)

ST: TDA 8145

There was a white/beige colored one that I couldn't identify and one or two others that I couldn't rad the logos on.


And two more pictures
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Offline Richard Crowley

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Re: Component video questions
« Reply #33 on: April 27, 2016, 02:37:25 am »
Maybe we need a much better description and photos of what you have there.
The photos don't show anything like what you were describing. Is this the same unit?
What "motherboard" are you talking about?
There appear to be all the sweep and driver circuits for the CRT display in the second and third photos.
But they are so close (and so fuzzy) it is hard to tell what we are looking at.
The board in the 2nd and 3rd photos look like the main board of the display.

I would think that the actual COMPUTER motherboard is some different board.
It is rare to find that the actual computer logic "motherboard" is combined with the display electronics.
Perhaps a larger photo of the whole thing would help us understand what you are talking about.
Since you are new to electronics, it appears that your verbal descriptions have led us astray.

I would expect that there is some cable (or bundle of wires) that has the RGB video signal out of the computer board, and going to the display main board.
It is at THAT point that you can discard the computer board and insert your RGB video signals into the CRT display.
 

Online helius

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Re: Component video questions
« Reply #34 on: April 27, 2016, 04:17:23 am »
Richard: The computer in question uses a custom high-voltage PCB that serves both CRT control and power supply functions, just like the Mac 128K.
The service documents, such as they are, do describe the components and how they connect (only FRU level information was made available).

You can see that the "analog board" with the flyback etc is uppermost, while the CPU slides in underneath. There is a harness that connects all the parts together including the disk drives, microphone, and speakers.
 

Offline Kilrah

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Re: Component video questions
« Reply #35 on: April 27, 2016, 06:04:54 am »
I guess that from the start he is confusing everybody by referring to the "analog" (display/PSU) board as "motherboard", when in computer terms that refers to the "logic" board below it.

So he's got the whole display circuitry, that takes something as input FROM the motherboard (likely RGBHV) and does everything to display it.

So we're back to what was said in the first thread - he needs test equipment and the knowledge to use it to find out what the different signals are in the interconnect between logic and analog boards, and once he's found that out see if his console can provide it... to which the reply is "likely not", since even if it supplies some RGBHV signal it won't have the proper timings being intended for TV. That would thus need a converter, which would be pretty complex.

TV and computer monitors while using similar technologies have always been 2 very different categories that wouldn't mix until recent flat panels.
« Last Edit: April 27, 2016, 06:08:54 am by Kilrah »
 

Online helius

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Re: Component video questions
« Reply #36 on: April 27, 2016, 03:39:58 pm »
That's true generally but there were always a few high-end (Sony) monitors that supported both video and computer display. Most computer monitors (aside from the Amiga) are non-interlaced, so they will not be designed to display interlaced video and it may not look especially good. But the major stumbling block to using SDTV resolution on a computer monitor is the scan rate, which at 15.7 kHz is much lower than most monitors are able to support. Aside from that hurdle there are many solutions to interface old video game consoles to RGB: http://retrorgb.com has many of them.

In the computer from the OP, the CPU board has an edge pin connector with many of the peripherals that would normally be external, including the monitor out. The old school Mac monitor connector has 15 pins that carry RGB, sync, and monitor identification to select the supported scan rates. The harness sets it to only use 640x480 @ 67 Hz. Displaying SDTV with the monitor is not possible unless the components that set the horizontal oscillator are changed.
 

Offline BobsURuncle

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Re: Component video questions
« Reply #37 on: April 27, 2016, 06:05:09 pm »
It is not clear to me the scope of your project - given the back and forth and exactly what unit or parts of the unit you have in front of you, but judging by your questions I can safely say you are way over your head.  Tackle something much simpler.   

I was an Applications Engineer and Development Engineer for a CRT manufacturer.  My focus was often integration of design for the CRT/deflection yoke and the horizontal and vertical sweep circuits of the TV or monitor.  Frankly, since I retired I haven't thought about the engineering even once and that was a decade and a half ago, so I am rusty as hell.  But I can tell you getting good performance out the system was a challenge for the pros.  Beside the analog circuitry design there is the  mechanics and electromagnetic optics involved in getting color purity, convergence and good raster geometry.  And the voltages involved are very high i.e. around 1Kv for the horizontal flyback and of course the EHT tap off of the flyback transformer is around 16KV or so.  Outside of the sync pulse from the component video, it has little to nothing to do with getting the tube to scan the screen.


 




« Last Edit: April 27, 2016, 06:08:49 pm by BobsURuncle »
 

Offline TRS-90

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Re: Component video questions
« Reply #38 on: April 27, 2016, 06:26:50 pm »
Okay let's get a few things out of the way.

The reason I sort of thought if would be easy to control the coils was because of this video:

I have all the required circuits to drive the machine I just need to feed it some signals (maybe a special signal or 2 to set the frequency to 15KHz)

I need to find out how only 2 sync outs on VGA drive to coils (because of the 4 wires on the board)

The CRT model number is: M 3 4 J N Q 1 0 X

The goal is to hook a playstation 2 via SCART to a 20+ year old color monitor because it looks cool.

Also how thick of gauge wire would I need to hook up wires to the CRT anyway?

And the thing I absolutely NEED is the harness or logic board pinouts and possibly the waveform that the keyboard's special power pin outputs.

Maybe a way to mod the PSU to turn on when to switch on the back is on instead of using the keyboard.
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Offline BobsURuncle

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Re: Component video questions
« Reply #39 on: April 27, 2016, 06:31:02 pm »
Here (hopefully) is an attached image file.
If this works then I will post some more so you can see what I have or don't have.
This one being the CRT running.

I DID NOT PRODUCE THE VIDEO SIGNAL IT IS FROM THE MOTHERBOARD THAT PLUGS INTO AN EDGE CONNECTOR.

Well, now I see you have a working display. So you just need to supply compatible video.
 

Offline TRS-90

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Re: Component video questions
« Reply #40 on: April 27, 2016, 06:34:18 pm »
OK
Someone said to make it support a 15KHz video signal I would have to change some components.

What would be the components that set the oscillator be out of curiosity?
I have a soldering iron and access to the internet.

And a way to discharge the CRT I got that part.

To find where to pins go I'd have to remove the analog board after discharging the tube.
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Offline Richard Crowley

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Re: Component video questions
« Reply #41 on: April 27, 2016, 07:37:44 pm »
What is the frame rate of your source? (some unidentified game console?)
What is the frame rate of the computer/monitor that you are trying to hack?

Many (most?) older, (and built-in, specific-purpose) CRT displays will operate only at their designed refresh rate.

Some later versions of standalone CRT monitors were "multi-sync" and had specially designed circuits to detect the incoming rate and change the internal circuits to accommodate the refresh rate.  See:  https://en.wikipedia.org/wiki/Multisync_monitor NEC had a very popular range of "MultiSync" monitors and in fact "MultiSync" is a trade-mark of NEC.  Of course, since modern LCD displays have essentially internal computers to interpret the incoming signal and drive the pixels, all modern displays are "multi-sync" by definition, and nobody even thinks about it anymore, it is just assumed.

But CRT displays that are made for a specific purpose, and especially those built-in to devices (like your unidentified computer) were most likely designed to operate at one fixed refresh rate. Because it is much more expensive to make a "multi-sync" CRT display. And if you have a fixed application there is no reason to spend the extra $$$ for multi-sync.

Unless your source (game console?) runs at the same refresh rate as your CRT display, you have another dilemma on your hands.  Changing the refresh rate for a fixed-rate display is for all practical purposes impossible for someone without significant experience with CRT circuitry.  IF it could even be done at all (and that is a very big IF), it would take far more work than simply finding a more suitable display. 

It is not just a matter of changing some components.  Most CRT displays use the same "fly-back transformer" BOTH to generate the extra-high voltage that accelerates the electron beam AND to create the horizontal sweep current.  Those two critical functions are inextricably combined together. It is quite a clever design to keep the cost of manufacture down to an affordable price.  But because it relies on a resonant, tuned circuit, it means the the magic is "baked in" and nearly impossible to change after the fact.

When I went to YouTube and searched for "discharge CRT", it listed "About 4,510 results".  The very first one "Micro Center Tech Support" seemed quite good.  Remember to discharge to the spring on the outside of the tube, and not to some point in the circuit farther away. Else you run the very real risk of zaping the computer mother board.

Remember that whenever you are working with the internals of any CRT display, you should be wearing good safety googles in case of explosion.  If you scratch the CRT in the wrong place, it will implode (from the vacuum), and then explode sharp shards of glass all over the place.  That is why people recommend against just using a grounded screwdriver or something that can scratch the glass tube.
 

Offline TRS-90

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Re: Component video questions
« Reply #42 on: April 27, 2016, 10:31:33 pm »
I plan on using SCART which is very similar to VGA that a normal computer monitor uses.
SCART just has sound and some extra features on the same cable.

The Playstation 2 might have a VGA mod that I could do and since the Logic Board outputs a VGA signal could that work?
Will something like this work?: http://poofycomputers.com/ps2vga/pics/ps2.vga.mod-chips.png

How do I find the video pins on the Logic Board myself if no schematic exists?

Also here is the other connector I have to deal with:
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Offline TRS-90

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Re: Component video questions
« Reply #43 on: April 28, 2016, 12:19:57 am »
I think I have almost all of this figured out I just need a way to make the power supply always be on instead of needing a signal to activate :-/O.

The PS2 AV out to VGA converter board I can make myself.

If I can make a mod for the PSU then I will be able to see if this is TRULY a lost cause (or just fail at soldering the chips).

 
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Online helius

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Re: Component video questions
« Reply #44 on: April 28, 2016, 03:10:09 am »
I plan on using SCART which is very similar to VGA that a normal computer monitor uses.
SCART just has sound and some extra features on the same cable.
SCART is just a connector type. The format of SD television (NTSC, PAL) is rather different from the format of a typical VGA monitor signal. The lines that make up a TV signal don't even begin and end in the corners of the screen, and the frequency that lines are drawn on the screen is lower.

Quote
The Playstation 2 might have a VGA mod that I could do and since the Logic Board outputs a VGA signal could that work?
Will something like this work?: http://poofycomputers.com/ps2vga/pics/ps2.vga.mod-chips.png
That just looks like a sync separator to me. It will, indeed, put the proper signals onto a VGA connector, but that doesn't mean any VGA monitor can display it. Monitors have frequency requirements and the last ones that supported both VGA and 15.7 kHz were made in the mid 1980s. After that, you could either get an increasingly high resolution computer monitor, or a SD video monitor/TV*; they couldn't display each others' signals, even with appropriate cables. After a few years the "computer" inputs on televisions disappeared because users weren't still using Commodore 128s.

Quote
How do I find the video pins on the Logic Board myself if no schematic exists?
You can reverse-engineer the parts of the schematic that you need. In this case, I guess you are interested in the card-edge pins that correspond to the Mac monitor cable pins, but see the issues above.
On the main board, see here, The video chip is the one in the lower right marked AT&T. The pins on the bottom side, opposite from the index dot, are R, G, B going left to right. You can test if any of these has continuity to one of the edge pins (the small section on the right half looks dedicated to video and possibly sound). Remember that each channel may also pass through a terminating resistor which will be nearby, on the top or bottom side of the board.

Quote
Also here is the other connector I have to deal with:
Just a regular card-edge connector.

*of course, at the time they weren't called "Standard Definition"; high-resolution television didn't exist yet, outside of limited broadcasts in Japan**

**not counting the black-and-white system used in France.
« Last Edit: April 28, 2016, 03:18:38 am by helius »
 

Offline Brumby

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Re: Component video questions
« Reply #45 on: April 28, 2016, 08:24:20 am »
I would put my efforts into acquiring a fully functional color CRT display.  Since most people are (or have) replaced their old CRT displays with modern LED/LCD/plasma, etc you should be able to find fully functional color CRT displays, (even broadcast-quality monitors that cost as much as your car) free for the hauling away.  However it is so late in the game that the supply of CRT displays is probably on the tail-end of complete extinction.

Indeed.  Just this last week I took a load to the recyclers.  Included was a fully functional Compaq 19" CRT monitor.  I just couldn't justify keeping it around.  I did, however, hang on to my 17" Philips.  It has dual input - VGA and 5x BNCs.
 

Offline TRS-90

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Re: Component video questions
« Reply #46 on: May 20, 2016, 01:16:08 am »
Wow. 
It's been awhile.

Anyway, I found a solution...almost.

There are composite video to VGA converters that actually work, but their minimum resolution is 800x600 while the monitor's resolution can't go that high.
Is there a way to make my own that will output 640x480?
(preferably costing as much as or less than $40)
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Offline Delta

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Re: Component video questions
« Reply #47 on: May 20, 2016, 02:48:16 am »
Wow.  I've only just read this thread.  Why on earth are you destroying a working vintage Macintosh in the vain hope that by some miraculous fluke you will be able to get it to display a different resolution, different frequency, interlaced image than what it was designed for.

I think this all started when you failed to realise that video signals don't drive deflection coils!  Applying some voltages to the coils to make the beam move around in no way whatsoever compares to displaying video!

Just find a CRT telly, stop wasting your time, and let the Mac have a nice retirement.


I know this sounds awfully condescending, but you have zero hope of getting this to work.  Please please please put your boundless enthusiasm into something else.

Peace.
 

Offline TRS-90

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Re: Component video questions
« Reply #48 on: May 20, 2016, 08:51:42 pm »
I haven't destroyed it, if I put it back together it would still work just fine.

The issue is that I can't find a SCSI HDD for it.

And actually this would work if I had the pinouts.

I can convert a composite video signal to VGA.

And yes while I could definitely find a great color TV for next to nothing I just want to use this tube because A. I have it and B. It works.

While I probably will give in and give up on this (as much as I would hate to) I at least would like someone to search for the schematic of the Mac Performa 577 analog board, at least.

Does this video help my cause at all?


But you all are probably right in telling me to give up on this...oh well, it was worth a shot.
PCBF ANALOG BD LC520/LC575/MACTV 820-0582-A, The bane of my existance.
 

Offline TRS-90

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Re: Component video questions
« Reply #49 on: May 20, 2016, 10:02:50 pm »
I refuse to start a new topic just for this so...


Would the library of congress happen to have the schematic?
(the board was made by apple's singapore branch)

Also where can I find 7000 series TTL chips besides the internet?

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