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I believe there's a way to rgb mod the Bally Astrocade...


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So I talked to this friend of mine who mods consoles and he has a friend who makes mod boards. I was told that the astrocade can do rgb through the same rgb mod board that the colecovision uses, but that you have to wire it up as the pins won't match up and that it has to have the TMS9918 chip.

 

I found these
Screenshot_20221002-130620.pngScreenshot_20221002-130625.pngScreenshot_20221002-130744.png?width=288Screenshot_20221002-131611.png?width=288

So there might be issues on one of the channels, the TMS chip is not marked so it's U18 on the board.

SCHEMATIC1___PAGE1.png?width=735&height=

So if you guys can confirm for me what TMS chip the bally uses, we can go from there. If it uses the TMS9928 or TMS9929, then it should work. Not 100% on it.

 

The board maker says;

The TMS9928A/9929A VDPs are functionally identical to the TMS9918A except that the NTSC color encoding circuitry
has been removed and replaced with luminance and color difference signals. The TMS9918A is pin-for-pin compatible
with the TMS9928A/9929A, except for three pins, the composite video output, the external video input and the CPU
clock output. These pins are replaced with the Black/White luminance and composite sync (V) output and two color difference pins, Blue (B-VI and Red (R-VI outputs, respectively. The color difference outputs allow the user to generate RedGreen-Blue (R-G-BI drive for direct color gun control, or composite video for use with NTSC or PAL video color monitor.
However~ to connect these three outputs to a R-G-B or monitor requires additional R-G-B or encoder circuitry. 

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7 hours ago, Johny_lovin_it said:

I was told that the astrocade can do rgb through the same rgb mod board that the colecovision uses

 

The Bally Arcade/Astrocade uses a custom chip that is only used in the Astroade and a few of Bally's arcade games, such as:

 

https://ballyalley.com/ballyalley/articles/astrocade_arcade_games.txt

 

I don't think that anyone has hooked up an Astrocade via RGB since the 1980s.  There is a bit about it on my website if you search it:

 

https://www.google.com/search?q=rgb+site:ballyalley.com

 

The Astrocade, luckily, does have a high-quality RF signal.  If you post to the Bally Alley discussion group, then you may find some more information there concerning S-Video and composite modifications:

 

https://groups.io/g/ballyalley

 

Have fun with your Bally console!

 

Adam

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3 minutes ago, Johny_lovin_it said:

Does that mean it should have like less interference and noise? And I'll check out the site you sent me, thanks.

 

Yeah, I think the RF signal on the Astrocade is pretty good.  Here is an example of some captured video footage from my own Astrocade.  This is video art, one of my favorite uses of Bally BASIC:

 

 

I have lots of Astrocade videos and all of the footage is captured from an RF signal going through a host of devices that probably degrades the signal before it is captured.

 

Of course, if you're looking for the cleanest picture that you can get, then RGB would certainly be the way to go, but in the end, you'll always have an analog signal from this console.  I used to chase the best picture I could get from all of my consoles, but now I've learned that the best picture will be to use traditional CRT TVs or monitors from the same vintage as the console or computer that I am trying to use.

 

Adam

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12 minutes ago, Johny_lovin_it said:

What is your opinion on the channel F? [...] What if I use like the thickest best quality a/v coaxial cable you get at best buy?

 

I don't own a Channel F, but my friend has one.  His wife calls it the "Channel Fail."  He uses RF and it looks okay on a flatscreen LCD TV that has RFin.  Using a quality RF cable may improve a poor signal, but I just go with old-school cables from the 1970s.  If it was good enough in the 1970s, then I guess it's good enough now.

 

Adma

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6 hours ago, Johny_lovin_it said:

What is your opinion on the channel F? I thought of having that modded too but with good composite. But perhaps like you said, depending on what tv I use, it may display clean pictures? What if I use like the thickest best quality a/v coaxial cable you get at best buy?

6 hours ago, Johny_lovin_it said:

 

Just wanted to share how pleased I am with the quality of the coaxial cable I recently purchased from Blue Jeans Cable. Their composite cable is also top notch.

Edited by LaserCat
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2 hours ago, LaserCat said:

Not the best picture but this is RF via an Aurora demodulator with component output into a Sony PVM20M2U.

 

Yeah, the picture looks great for composite.  I have a similar setup using different hardware, but the results seem about the same.  In your next post you mention Blue Jeans Cable.  I'm not familiar with them.  Are you referring to this RF cable that they sell:

 

https://www.bluejeanscable.com/store/rf/index.htm

 

Maybe I'll pick one up.

 

Adam

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Yes, the 1505A. I always assumed the company name indicated a cheap product but I was wrong. They are made to order in Seattle, WA, using Belden brand cable. I believe they have a money back guarantee. I just wish the Astrocade didn’t have a hard wired cable because I prefer the option of choosing which interconnects I use. Here is a random video of their shop in action.

 

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Maybe modding this console isn't that big of a deal if the RF cable is high quality. I've ordered one of those a/v cables from best buy, i'm going to test this console out and see how good it looks. First I need a game. I saw this one on ebay called cosmic raiders and it says reproduction. Is this a homebrew or was it a commercial release?

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9 hours ago, Johny_lovin_it said:

Maybe modding this console isn't that big of a deal if the RF cable is high quality. I've ordered one of those a/v cables from best buy, i'm going to test this console out and see how good it looks. First I need a game. I saw this one on ebay called cosmic raiders and it says reproduction. Is this a homebrew or was it a commercial release?

It is a reproduction of a rare game. I own a copy and it is the game in screenshot a couple of posts prior to this one. There is also a prototype version which I do not own. For some reason the Astrocade is the only system I have that I just don’t need to own original copies of the games.

 

 

Edited by LaserCat
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10 hours ago, Johny_lovin_it said:

First I need a game [for my Astrocade].

 

If you don't have any Astrocade games, then get the multicart for the system.  It's made in low-volume, but it's still made.  The cartridge is called the UltiMulti.  Pictures of it are here:

 

https://ballyalley.com/pics/cartridge_pics/Carts_(Multicarts)/multicart_(GaMBITS)/multicart_(GaMBITS).html

 

Allen Schweitzer is the person who makes these cartridges that were designed by Ken Lill.

 

There is also the new BackBit cartridge and adapter for the Astrocade.  You can read about it here, in this thread:

 

 

While this BackBit cartridge, which uses a MicroSD card, and thus can be updated by the end-user, might seem ideal, it can only be used to play normal games from cartridge, so there are quite a few games that can't be used.  Also, Allen still makes another expansion, in small quantities, called the Lil' White Ram, which looks like this:

 

https://ballyalley.com/pics/hardware_pics/Lil_White_RAM/Lil-White-Ram.html

 

This is a RAM expansion unit that allows the user to play most of the games on the UltiMulti cart that require extra RAM.

 

I hope you enjoy your Bally Arcade console, no matter how it's hooked up to a TV.

 

Adam

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@Johny_lovin_it I'll assume you heard this from me?

Any of these old consoles can have a CPLD/FPGA mod made to make RGB video. 

The hard part is making them. A CPLD/FPGA kit for the coleco (as the one you posted is) would not work on the Bally. 

An analog kit for the coleco (such as the TMS RGB) could be tweaked to work on the Bally

 

The Bally (and the colecovision). Both mix R-y, B-y, and Y to make

RF. YPBPR is more or less equitable to RGB. 

These two consoles both use a LM1889,. So a circuit designed to mix from the inputs of the LM1889 (YPbPr) could be made to work on both. With TMS-RGB possibly being a base for that.

 

TLDR the circuit would be:

Sync stripper

Analog mixing circuit (to mix RGB from YPbPr) [needs blanked on sync; possibly blanked on blank if available]. 

Video is boosted somewhere around sync on the coleco (PB?) and on both Pb and Pr on the bally. 

 

NAQpbp8.png 

 

This is on the bally; one of these yellow lines is Pb, and the other yellow is Pr (idk which is which), the purple like is Y. 

TLDR to the TLDR; Analog mixing RGB from YPbPR is possible but these humps during blanking need stripped out or it will effect the colors (this is the main issue with making this mod).

How best to do that is what is the limitation atm. Ill have to think about it. 

 

EDIT:

That kid posted has an EPROM M27C1001; I am not sure what the rest of the circuitry is but probably analog mixing; either way this wouldn't be useful to do the Bally's RGB mod. I will make something for the Bally before the year is up. Pinky promise. 

Edited by the_crayon_king
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I don't want to double post but the gist of what I am seeing after building out what is needed to "blank" Pb and Pr for the Bally means the TMS-RGB circuit (as it is) will NOT work. 

You need to sample and hold a value when R-Y and B-Y are actually not active and then use it where it should be blanked (around sync).

Else you could make two VREFs with resistor dividers and a reference voltage. 

Either way you would have to have an analog switch that toggles between this reference/hold value (when at blank) and the current value of b-y/r-y (when not blank). 

I am currently working on how to cut down the parts needed to do this but the rough circuitry is complete.

Once YPbPr is corrected then it will be easy to split and send one out to the LMH1251 to make RGB and another as a corrected Component output.

 

I will make my own post on the topic once I get a bit closer to a final design. PM me with any thoughts or O-scope samples of these relevant issues.

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