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Gunstar

7800 DIY mods/upgrades and commercial kit upgrades?

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Posted (edited)

The last time I owned a 7800 pretty much the only upgrade DIY or otherwise was the Audio/video mods and of course the PSU mod to barrel style. But I've heard tell of much more in brief references while reacquainting myself with the 7800 community and what has transpired, been released or created to expand and modify the 7800. I'm a hardware tech guy buy nature, and modify and upgrade as much as I can cram inside most of my vintage machines, the descriptions of my two Atari 8-bits being prime examples in my signature below (blogs now and coming soon in my profile for many of my mod/upgrade/hack jobs).

 

I've got 25-30 years of electronics experience and education under my belt, so nothing is out of my league. I can and have created my own upgrades and could do the same for myself with the 7800, but I'm a procrastinator, would rather be lazy and just build designs by others,and short on time much of the year (with a 101 projects I'm already in the middle of) and then plenty of time over the winter with my seasonal business, so I'd rather just build or buy and install other's designs if I can.

 

Sometimes I'm forced to design my own from scratch like I did with my Atari 800 dual-PIA* board, with a co-conspirator. Only a few boards were made for our own use (image of installed board below), nothing for sale, though we will freely give schematics and gerber files, etc. to anyone who cares (Soon to be added to my 800 upgrade blog). Born out of wanting something more professional than the piggy-back DIY hack-job instructions available online for Atari 8-bit dual PIA upgrades and more forward thinking for future expansion. It's an extremely niche upgrade though, it's purpose to add an additional 4 controller ports to the 800/XL/XE line, meant for control and communication with external hardware like other computers, LAN, robots, sensors, basically anything you want. the extra I/O I need for research and development using the 800 as a controller/manager. I also included board layout and 3D models of earlier revisions. I think we ended up going through 7-8 revisions, most just changing the real estate to make it fit in the 800 under the shield, best spot for connections, and with other upgrades like the Pokeymax Quad + Covox I installed.

 

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For the 7800, one mod/upgrade I'm interested in, if one exists, for the 7800 is switching between PAL and NTSC standards in one console. This is easy with some consoles and computers (like the Jaguar) and involved and difficult for others. Also, did anything finally come of the 7800 XM module? I thought it became vaporware except for prototypes, but I've heard brief mention of the XM is some thread or other. Are there DIY alternatives now? Of course I want to know about everything including ram upgrades, IC upgrades, etc

Edited by Gunstar

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Posted (edited)
3 hours ago, Gunstar said:

For the 7800, one mod/upgrade I'm interested in, if one exists, for the 7800 is switching between PAL and NTSC standards in one console. This is easy with some consoles and computers (like the Jaguar) and involved and difficult for others. Also, did anything finally come of the 7800 XM module? I thought it became vaporware except for prototypes, but I've heard brief mention of the XM is some thread or other. Are there DIY alternatives now? Of course I want to know about everything including ram upgrades, IC upgrades, etc

PAL/NTSC would likely be overly complicated, likely requiring multiple different ICs and the sacrifice of donor 7800's to get them. I'd have thought you'd at least need both PAL and NTSC TIA and MARIA ICs and a region free BIOS (though that exists with another in the works). Different clocks also, not to mention the way the clocks are propgated is different between the machines. It also only becomes a benefit if you have a mixed selection of carts and even then it is just easier to have both machines.

 

XM development stopped when the guy doing it passed away. The closest alternative is the Dragonfly cart that RJ makes. It is a flash cart but it has the POKEY & YM sound chip on there, and extra RAM. Most, if not all XM specific games have already been fettled to work on it.

 

The outstanding holy grail for the 7800 is still the RGB mod. Both Tim Worthington and Saint have been on with this, the former for years. Again, it's complicated by the 7800 essentially having two video sources depending on whether you put a 7800 or 2600 game in and neither of them giving you an easy time given the signals they output. This would be of particular benefit to a PAL machine as it's PQ is lousy, and though it can be brought up to acceptale with a few mods, it's not a patch on the NTSC machine just with a UAV on it.

Edited by juansolo

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Posted (edited)

OK, I've posted to be put on the Dragonfly pre-order list for the basic model, I have a Pokey to use. I have a Pokeymax v3 too, I could use, if there's anything on the 7800 to make use of it, otherwise it goes in an Atari 8-bit, but right now the A8 is down for repairs anyway, I'm also not interested in YM2151 board until there's something for it on the 7800 then I'll get one. So that will give me Pokey and ram. I'll look into this RGB mod, that does interest me. My Jaguar and Genesis 1 (Megadrive) are both using RGB output and I have a wonderful RGB-to-VGA converter/upscaler to use with any PC monitor or TV, CRT or LCD that has a VGA input. I prefer my 20" CRT VGA monitor. Of course I do have a CBM 1084S monitor with RGB too.

Edited by Gunstar

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5 hours ago, Gunstar said:

I'm also not interested in YM2151 board until there's something for it on the 7800 then I'll get one.

Bob D.’s Pac-Man Collection 40th Anniversary Edition uses it and it sounds amazing. The TIA-only version is quite excellent, but the YM version sounds superb. There are also a few more demos that take advantage of it. Given the low price, I don’t know why everyone doesn’t add one, if for no other reason than to encourage developers to take advantage of it.

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8 minutes ago, DrVenkman said:

Bob D.’s Pac-Man Collection 40th Anniversary Edition uses it and it sounds amazing. The TIA-only version is quite excellent, but the YM version sounds superb. There are also a few more demos that take advantage of it. Given the low price, I don’t know why everyone doesn’t add one, if for no other reason than to encourage developers to take advantage of it.

In that case I will change my pre-order to include it, since I have one or two YM's on hand anyway too. Thanks for the heads-up and correcting me about the YM compatible software.

 

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The only reason I was interested in a possible PAL/NTSC 7800 mod is that I've discovered that the prototype game 'Missing In Action' is apparently NTSC only. I had thought only PAL 7800's had exclusive software. But since there is no simple mod I can live with just a PAL 7800. It's not worth getting an NTSC machine for this one unfinished game. I'll just have to suck it up and check it out under emulation on my DC (I don't do emulators on PC's, but I don't mind emulating some through my DC or Xbox.

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Lots of info has been given already. But for the current time, if you want the best picture quality from a 7800. Your best bet is to go with an NTSC model unit, put one of the modified BIOS chips in it that would allow it play most PAL games (Some will have graphical glitches or not work but I haven't a list of what does or doesn't work). And then stick a UAV in it with the recently found chroma timing fix using a 4050 buffer IC for the 7800 side. That will give you the best of what you can get from a 7800 until Tim or SaiNT have an RGB solution in place.

 

The PAL systems from what @juansolo has stated in other threads here, requires a LOT of work to get a good picture out of it and even then, it still doesn't compete with an NTSC unit with just a UAV installed. 

 

If you have PokeyMAX you might want to put that into your DF cart since with PokeyMAX the DF can have it emulate dual pokeys along with Covox speech. While no games have been developed or are in development using these features, there are demos that do that are quite impressive. RJ is also working on a separate add in cart for just the YM2151 so that other game devs will make use of it and have a much cheaper option for people to get to take advantage of the YM sound without having to spring for the full DF cart.

 

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There are no PAL exclusive 7800 games. There are several NTSC exclusive 7800. If you are getting a mulit-cart it is better to go NTSC if your TV supports it.

 

Mitch

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2 hours ago, Mitch said:

There are no PAL exclusive 7800 games. There are several NTSC exclusive 7800. If you are getting a mulit-cart it is better to go NTSC if your TV supports it.

 

Mitch

I think some of the PAL versions of the games are cheaper than their NTSC couterparts though? That is the only reason I've seen for anyone wanting to use strictly a PAL console 7800 over the NTSC model.

 

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1 hour ago, -^CrossBow^- said:

I think some of the PAL versions of the games are cheaper than their NTSC couterparts though? That is the only reason I've seen for anyone wanting to use strictly a PAL console 7800 over the NTSC model.

 

True, but if he is getting a SD card based multi-cart that doesn't really matter. :)

 

Mitch

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I recently purchased my first  7800 and I plan to install the UAV right away.  I noticed that the online instructions have a S-video connector pictured for luma/chroma and RCA connectors for composite and audio.  Has anyone done this mod and used the 5-pin DIN.  

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59 minutes ago, hueyjones70 said:

I recently purchased my first  7800 and I plan to install the UAV right away.  I noticed that the online instructions have a S-video connector pictured for luma/chroma and RCA connectors for composite and audio.  Has anyone done this mod and used the 5-pin DIN.  

i haven't only because I like using standard cables that I can get anywhere and I only have standard s-video and RCAs on hand for most stuff. Same for most of my clients as well. But you are talking about a combo din like what was found with many video capture cards back in the day for PCs correct? Another problem with a combo cable like that is that all of the input signals will be sharing the same ground and I've seen interference kinda like jail bars appear through s-video when it shares the ground with the composite. I run separate ground wires so that only the composite and audio share one ground, and then I use another ground to tie the grounds from chroma and luma together on another wire.

 

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I'm planning to use the same cables that I use with my Atari computers. My monitor of choice is a Commodore that has luma, chroma, and composite inputs.

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11 minutes ago, hueyjones70 said:

I'm planning to use the same cables that I use with my Atari computers. My monitor of choice is a Commodore that has luma, chroma, and composite inputs.

Makes sense but just stating what I've seen when using the same ground for composite, s-video, and audio all at the same time on the 7800s I've done. Another option if you are trying to minimize case modification is to use a 4 conductor TRRS jack to at least handle the composite and audio and then use an s-video output jack with one of those chroma/luma splitters on it for your commodore monitor. Then again, using a CRT you might not see the jail bars that I see when using flat panel modern displays.

 

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I just finished installing a composite video mod in my 7800. The mod kit was less than $10 and the picture is very good on a dell monitor and a flat screen TV. I don't know if I will bother with the UAV.

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I'm in the middle of my own flavor of S-video/audio mod/upgrade. I didn't like what I saw out there for DIY upgrades, so I'm extrapolating from a couple as well as trying some ideas for a cleaner picture, It will be S-video out only, as I have an Svideo2composite inline adapter if I need composite for some reason. The two RCA jacks already installed for a poorly done composite & audio conversion will be used as dual-mono output to hook up L/R speakers (yes I know a simple RCA splitter works for this, but the jacks are already there and removing them leaves holes I'd have to repair).

 

I'll also be hacking my Dragonfly device right after with a DIY stereo output on it for the YM2151. And I think I may do a DIY piggy-back dual-Pokey mod too, with real Pokey's since Pokeymax's specifically programmed for the DF are not available. No Covox that way, but it's all hard-wired and needs no special programming. That depends on if there is room under the DF hood for a piggy-backed chip set.

And of course since the DF has expanded memory too, I guess I won't need any other internal upgrades for the 7800, except maybe a custom OS chip.

 

By the way, in my PAL 7800 the OS chip has pin 27 lifted and a wire running from it to the motherboard nearby, next to the R74 resister for color-burst. I tried tracing where it was going, but am not quite sure with components in the way and it's hard to make out traces. I think it's either going direct to ground or to the 6502 or Maria. I see no issues with the mobo or socket that should require a bypass. Looking at the schematics OS pin 27 on the mobo appears to be connected to the A14 lines of the 6502 and Maria, but as I said I was unable to verify for sure where the bypass wire is connecting. Is this a custom OS IC I have already? Does anyone know what this mod is for? (see pic below)

 

 

20210829_092242.jpg

Edited by Gunstar

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On 7/24/2021 at 1:16 PM, Mitch said:

There are no PAL exclusive 7800 games. There are several NTSC exclusive 7800. If you are getting a mulit-cart it is better to go NTSC if your TV supports it.

 

Mitch

SENTINEL was only released as PAL, but you can get an NTSC reproduction of it (as I did for my collection). Still looking for NTCS Ninja Golf and NTSC Tank Command to finish off my library.

 

I also have the ATARI 7800 32-in-1 PAL only exclusive (even though it's just the ATARI 2600 32-in-1 PAL rebadged)

Edited by NISMOPC
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On 8/29/2021 at 9:26 AM, Gunstar said:

On my PAL 7800 the OS chip has pin 27 lifted and a wire running from it to the motherboard nearby, next to the R74 resister for color-burst. I tried tracing where it was going, but am not quite sure with components in the way and it's hard to make out traces. I think it's either going direct to ground or to the 6502 or Maria. I see no issues with the mobo or socket that should require a bypass. Looking at the schematics OS pin 27 on the mobo appears to be connected to the A14 lines of the 6502 and Maria, but as I said I was unable to verify for sure where the bypass wire is connecting. Is this a custom OS IC I have already? Does anyone know what this mod is for? (see pic below)

 

 

20210829_092242.jpg

I asked above, but it might have gone unnoticed at the end of my post, so I'm quoting myself to bring attention to the question I asked since no one responded to it the first time.

Edited by Gunstar

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No PAL 7800 we've ever dealt with has had that bodge. Then again none of them have had the 001 revision of that IC either... I doubt it's a factory bodge, but then I've seen them do worse (even fitting their bodges in the wrong places...), so who knows. R74 is the PAL colour burst for the MARIA, it shouldn't be connected to that, so it's likely going somewhere else.

Edited by juansolo
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