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Odyssey 2 AV board?


Dopy25

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I am looking for information on a composite mod for the O2. I just got one, and while it works over RF, that adapter is weird. I would much rather have RCA jacks. I don't have anything that can run RGB so that would be overkill. I found a few mod boards for sale on ebay, but 5 components that I already have on hand for over $30 seems excessive. Is there any information on open source boards that I could build? I have a spare board for a 2600/7800 resistor/transistor mod as well as an LM315 amp board for a colecovision. Would either of those work by pulling the power and video input from the respective RF lines?

 

I found a few threads for RGB mods, and one or 2 for composite, but they didn't lead me anywhere closer to building my own. I found that you can run wires directly from some connections on the board, but that has mixed results. I haven't tried any of them yet since it just came in the mail yesterday. Just looking for info and some ideas.

 

Thanks!

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I think the board you are referencing is mine? I think people only see a linear cost of the sum of parts not the cost of RnD, shipping, ebay fees, labor, etc.

Labor being the largest part of my costs since I value my time. I did make another board "Orange Peel" that can work with the O2 just the same while shooting out S-Video and Composite.

It is even slightly cheaper (30). 

 

I had/have an open source RGB design for the O2 someplace out in the ether. I also had an open source RGB to S-Video/Composite board. If you married those two parts you could get more or less the same composite video you would get out of the more expensive solution.

The only difference is you would be doing the labor of allocating and assembling the parts instead of me (saving money).

 

I assume you want to do the simplest thing? Which would be to take the video from pin 5 of the 612160-1 > resistor divider (depending on the p-p) > op amp > 75 ohm resistor > + 220uf capacitor -.

 

If someone gives me the p-p of video at pin 5; I could give more specific advice on the circuit you could build. 

Edited by the_crayon_king
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3 hours ago, the_crayon_king said:

I think the board you are referencing is mine? I think people only see a linear cost of the sum of parts not the cost of RnD, shipping, ebay fees, labor, etc.

I think I saw a board of yours and one from grips. I did not mean to offend at all. I completely understand the cost and time you've endured. I only meant that an RGB solution is far elaborate for my wants. I don't have anything to support RGB and putting something like that in any system I have, only to use it for composite or s-video seems like a waste to me, and a slap in the face to whomever made the board. I wouldn't be using it at it's fullest potential. I WISH I had something that could support the RGB of the boards you make. 

 

The board I see for $30 on eBay isn't much of a thing. I guess I do kind of gloss over the cost that went into creating that but it just seems simple to me. Not at all like the RGB boards like yours that I've read about.

 

I've read about a composite output that uses direct wires from the board to RCA jacks, but the results are often too dim. 

 

I guess what I'm looking for is something simple

3 hours ago, the_crayon_king said:

If someone gives me the p-p of video at pin 5; I could give more specific advice on the circuit you could build. 

I'm not sure what you mean here. What is p-p? The O2 I have works and I have a multi meter. No oscilloscope. Is that finding something I could provide?

 

Edit: Oh. I totally forgot. This orange peel you made, it does s-video out of the O2 and costs roughly $30? I would spend that for sure as I would love s-video.

 

Edited by Dopy25
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@Dopy25 Trust me I'm not offended at all. I see lots of things where I don't want to pay X so I make my own.

The newer board was to support people who had S-Video or Composite instead of RGB. I already have to make RGB in order to make composite and S-Video. So it is not wasted or anything.

 

Yes the Orange Peel board can be made to work on the O2 depending on how I flash it.

I hadn't gotten around to testing those yet. 

 

If you are after something you can make yourself then I have a a rough idea of the design you need. I probably already have most of it made someplace. 

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269301319_Schematic_SimpleCompositeDriver_2021-12-22.png.c92b32dce29c2efd7ec9861e554a8d2e.png

 

That should be limited to 2.5V max out. Which should make it pretty safe? You would adjust the pot until you had video as bright as you needed.

 

So from left to right: 

1k/1k resistor/divider (cuts video voltage in half).

0.1uf capacitor blocks DC.

The two 800k resistors set a new known DC offset. In this case 2.5V

R3 and RP1 (potentiometer) are for setting the gain. 

RS8751XF is the op amp I picked for a number of reasons. 

Lastly the 75 ohm resistor and 220uf capacitor are something you see on every video circuit.

 

I didn't put a ton of thought into this so there may be some fatal flaw I haven't considered yet. I think a circuit like this can work in almost any situation to get basic composite video. 

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https://oshpark.com/shared_projects/ybW8wB06

 

image.thumb.png.897da625da32c2a296a395a6149d4b76.png

image.thumb.png.fa20967ea3c6ba7fdea8b96848be33ad.png

image.thumb.png.e0d75d03567e89c90fd439dafb26787b.png

 

That is the general idea. I used 45deg ARC for the traces instead of the normal way (line 45). 

First time ever using that and probably won't ever use it again. 

 

A lot of the resistor values I used are arbitrary but since there is a 10K pot to adjust everything I am not sure that it matters.

When soldering start with the SOIC-8 IC since it will be easier before all that stuff is in the way.

Make sure to shield the bottom (where the through holes are) from touching anything conductive.

 

More details on the OSHpark page.

And specific items needed are written on the bottom of the board.

Gerber_PCB_Simple Composite Driver_3_2021-12-22 (1).zip

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Holy crap, man. I really feel like you went out of your way on that one. I greatly appreciate it! I will check it out and have a few boards ordered. I only need one though. I'll either part with the rest at cost, or send them to you if you want them, tbh.

 

You said that is the general idea, but it appears to be a completed board. Would you say that will get a composite output for sure? Looks kinda similar to the 2 transistor mod, but using an amp instead which would give much better results.

 

You're awesome with video circuits and I appreciate all the work you do. Hopefully I can get an RGB setup one day and use most of the boards you make.

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38 minutes ago, Dopy25 said:

Holy crap, man. I really feel like you went out of your way on that one. I greatly appreciate it! I will check it out and have a few boards ordered. I only need one though. I'll either part with the rest at cost, or send them to you if you want them, tbh.

 

You said that is the general idea, but it appears to be a completed board. Would you say that will get a composite output for sure? Looks kinda similar to the 2 transistor mod, but using an amp instead which would give much better results.

 

You're awesome with video circuits and I appreciate all the work you do. Hopefully I can get an RGB setup one day and use most of the boards you make.

I wouldn't rush to use it. I will probably make some changes to the values. 

For one I think a 1K pot will be more appropriate. Since you would have 28 turns through 1K instead of 28 through 10K. So if I am understanding that right 1k will be more tunable (inside the needed range). 

 

 

I'll measure the Intellivision and see what its RF values are (before getting turned into actual RF). Since depending on the p-p it could change the values here.

I order through https://jlcpcb.com/ which might take longer but it is probably cheaper. It is certainly cheaper in bulk.

 

I don't need any of these so save them or send them out. You or anyone could sell these boards too since I have no intention of doing it. 

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Awesome sauce. I understand the change in values. I could make those easily enough. But the board itself is complete? I'd be willing to order them now if the only thing that changes are the values of the pot and resistors. 

 

I'm still not sure what p-p is. I know very little about actual video circuits. 

 

Cool beans. Thanks for the permission. I would only sell off the excess from a minimum order I would have to make in order to make it reasonable. Wouldn't be a regular thing. I still have 2 boards for a colecovision from the last time I bought from osh and the min was 3. Those are going up for a few bucks soon as well. Just haven't been in a rush or need to offload them. 

 

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6 minutes ago, Dopy25 said:

Awesome sauce. I understand the change in values. I could make those easily enough. But the board itself is complete? I'd be willing to order them now if the only thing that changes are the values of the pot and resistors. 

 

I'm still not sure what p-p is. I know very little about actual video circuits. 

 

Cool beans. Thanks for the permission. I would only sell off the excess from a minimum order I would have to make in order to make it reasonable. Wouldn't be a regular thing. I still have 2 boards for a colecovision from the last time I bought from osh and the min was 3. Those are going up for a few bucks soon as well. Just haven't been in a rush or need to offload them. 

 

P-P is the range of active video. So if something is 1V p-p it goes up and down by that much,. 

The DC component is what the AC rides on. So if you have 1V p-p on a 2V DC offset then you would have a signal that goes 1.5V to 2.5V 

If you had that same signal with no DC offset it will go negative 0.5V to positive 0.5V. 

 

 

Do not order this board. I am pretty sure this has a major flaw in that it can only set the gain within a narrow margin since the DC component would be multiplied too?

The board would work provided you did alot of extra work. My goal was to not do that and have something tunable within a range. 

 

I can still do that but I have to change the design. So instead of adding a DC offset I am just going to block DC but then have the op amp use a negative rail (so no offset will need added back).

 

 

 

 

  

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1 hour ago, the_crayon_king said:

P-P is the range of active video. So if something is 1V p-p it goes up and down by that much,. 

The DC component is what the AC rides on. So if you have 1V p-p on a 2V DC offset then you would have a signal that goes 1.5V to 2.5V 

If you had that same signal with no DC offset it will go negative 0.5V to positive 0.5V. 

 

 

Do not order this board. I am pretty sure this has a major flaw in that it can only set the gain within a narrow margin since the DC component would be multiplied too?

The board would work provided you did alot of extra work. My goal was to not do that and have something tunable within a range. 

 

I can still do that but I have to change the design. So instead of adding a DC offset I am just going to block DC but then have the op amp use a negative rail (so no offset will need added back). 

OHHH I see. SO it's the voltage. I believe I can measure that. I think that if I gave you the voltage rating from the video output at the rf, you would be able to tell. Is that right?

 

No problem. I won't order that as a board. Not unless you say it's good to go, or think it will work at all. As I mentioned, I know very little (if anything, considerably) about video circuits.

 

Thank you!

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25 minutes ago, Dopy25 said:

OHHH I see. SO it's the voltage. I believe I can measure that. I think that if I gave you the voltage rating from the video output at the rf, you would be able to tell. Is that right?

 

No problem. I won't order that as a board. Not unless you say it's good to go, or think it will work at all. As I mentioned, I know very little (if anything, considerably) about video circuits.

 

Thank you!

The voltage needs to be measured with an o-scope not a multimeter.

My O2 says 740mv p-p; 2.60 high 1.86 low. 

 

I know roughly how to make a circuit without adding a rail splitter or anything else. I am fudgeing around for a sec cause I don't remember EXACTLY how to make it but it involves inverting the video signal twice and adding offsets that way.

I am pretty sure I can make that work at least. 

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8 minutes ago, the_crayon_king said:

The voltage needs to be measured with an o-scope not a multimeter.

My O2 says 740mv p-p; 2.60 high 1.86 low. 

Ah. Yup. Don't have one of those. I could maybe acquire one, but TBH I don't have the first idea how to use it. I've seen the images from your posts but I don't know what they mean.

 

9 minutes ago, the_crayon_king said:

I know roughly how to make a circuit without adding a rail splitter or anything else. I am fudgeing around for a sec cause I don't remember EXACTLY how to make it but it involves inverting the video signal twice and adding offsets that way.

I am pretty sure I can make that work at least. 

Sounds like the video mod board on ebay. 2 transistors and a few resistors. No amp though.

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1 hour ago, Dopy25 said:

Ah. Yup. Don't have one of those. I could maybe acquire one, but TBH I don't have the first idea how to use it. I've seen the images from your posts but I don't know what they mean.

 

Sounds like the video mod board on ebay. 2 transistors and a few resistors. No amp though.

This should actually work. There are many ways to do this but this made the most sense to me without adding additional components.

1615364706_Schematic_SimpleCompositeDriver_2021-12-22(1).thumb.png.b2e237eb2ed4d1b5db3e1fb254c1aa03.png

 

From the measurements of my O2:

740 MV p-p means it needs a gain of 2.70 to reach 2V p-p. 

2.60 was the max voltage so if you times that by 2.70 you get 7.02

 

1.86 was min voltage x 2.7 = 5.02

7.02-5.02 = 2.02 p-p (which gets further reduced to 1.01V p-p).

The problem of trying to do that is 7.02V is too high of a voltage to deal with. Thus all the circuitry needed to fix this.

 

If you use a capacitor then only the p-p should be relevant but the value of that would be 740/2 = 370. So 370 + and 370 -.

Something I cannot use without adding my own DC offset or going out of the way to do it the above way in order to have more range of possible input values. 

 

 

TLDR I cannot see how the transistor mods out there could function with so few components. I would wager the darker video has something to do with that. 

 

I will make a board out of the above once I am sure I don't want to change anything. Could be wrong completely IDK. 

 

 

 

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The summary of this solution is how to amplify a signal with various amounts of gain, while blocking DC, without using a negative power rail. I think this does that?

Should work with almost any console with RF not just the O2; make sure to remove audio from the RF line if it is connected. 

image.thumb.png.1f0b3b853e97d360133e7691a9e71ec7.png

 

https://oshpark.com/shared_projects/V8fikyx4

The resistor marked XK can just be a 1K resistor. I may adjust any and all of these values. 

Potentiometer is this : https://www.digikey.com/en/products/detail/nte-electronics-inc/500E-0200/11651809

The turns to resistance ratio is what is important I think. Notice the footprint of the pot does not match the boards footprint. This is fine just focus on the location of pin 1 and place accordingly. (pin one is marked with a circle).

 

TLDR the wiring makes sense to me and I personally would try it if I had one. I am 80% sure this will work but feel free to correct me if I am wrong.  

As always do your own DD. 

 

Dimensions 2.5X1 inch.

 

Play around with the simulation and see if it makes sense: https://tinyurl.com/y2e7493j

 

Gerber_PCB_Simple Composite Driver_2021-12-24 (1).zip

Edited by the_crayon_king
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