7800 Robot Tank mod

[shear_xear]

Hi everyone.  I’ve notice in the past people have spoken of a mod for the 7800 which allows consoles that were previously incompatible with Robot Tank and other bank switching games to be compatible.  All of these links appear to now be dead.  Does anyone know where this information might still exist?  Thanks!

[Shawn]

 

[shear_xear]

Thanks!! My search didn’t find this one for some reason.

[phoenixdownita]

for posterity:

 

https://books.google.com/books?id=bGEbLt1C168C&pg=PA231&lpg=PA231&dq=7800+c64+resistor+mod&hl=en#v=onepage&q=7800 c64 resistor mod&f=false

[John Stamos Mullet]

To simplify without links:

 

Remove the capacitor at C-64, on the right hand side of the board between two ICs. That's it.

 

You can build a clunky add-on timing circuit from the above linked design, but that is so you don't lose compatibility with the 2600 version of Dark Chambers (which is kind of irrelevant on the 7800, since the 7800 version of Dark Chambers exists and is loads better, and easier to obtain.

 

The real fix to ensure you can use Robot Tank, Space Shuttle, The Activision Decathlon, and the Starpath Supercharger is to just remove the capacitor at C-64. You can even just clip one leg if you want to retain it in case you decide to build that timing circuit for 2600 Dark Chambers.

[+-^CrossBow^-]

6 minutes ago, John Stamos Mullet said:

To simplify without links:

 

Remove the capacitor at C-64, on the right hand side of the board between two ICs. That's it.

 

You can build a clunky add-on timing circuit from the above linked design, but that is so you don't lose compatibility with the 2600 version of Dark Chambers (which is kind of irrelevant on the 7800, since the 7800 version of Dark Chambers exists and is loads better, and easier to obtain.

 

The real fix to ensure you can use Robot Tank, Space Shuttle, The Activision Decathlon, and the Starpath Supercharger is to just remove the capacitor at C-64. You can even just clip one leg if you want to retain it in case you decide to build that timing circuit for 2600 Dark Chambers.

This is almost 100% accurate. But on most 7800s I've worked on including one of my own personal test units. Decathlon doesn't work regardless of C-64 being active or not. Also Mitch recently stated that the timing circuit might be needed by Defender II/Stargate as well as 2600 Dark Chambers. And while 2600 Dark Chambers might not be that great a game, there are some decent hacks using that game at the core so... just other stuff to be aware of.

 

But I actually de-solder the right leg of that cap on each 7800 I service when I find it and let the clients know it has been done. Because as you noted, it make way more stuff work and be compatible again vs not.

 

[John Stamos Mullet]

8 minutes ago, -^CrossBow^- said:

This is almost 100% accurate. But on most 7800s I've worked on including one of my own personal test units. Decathlon doesn't work regardless of C-64 being active or not. Also Mitch recently stated that the timing circuit might be needed by Defender II/Stargate as well as 2600 Dark Chambers. And while 2600 Dark Chambers might not be that great a game, there are some decent hacks using that game at the core so... just other stuff to be aware of.

 

But I actually de-solder the right leg of that cap on each 7800 I service when I find it and let the clients know it has been done. Because as you noted, it make way more stuff work and be compatible again vs not.

 

I had on 7800 that didn't like Decathlon, but then I also have two others that it runs fine after the fix. As always the 7800 is a complete crapshoot.

 

I've never had a problem with my Stargate running on any 7800 or 2600, but at one point I did buy one off ebay that rolled like crazy on everything - turned out it was a loose PAL copy, but there's really no easy way to tell.

 

The really easy answer is to get a Harmony cart, because then you don't have to mod anything and they all work!