I must be stupid ... how do you build bankswitched 2600 carts?

[jaybird3rd]

Okay, I've got an EPROM burner and eraser, I have a whole mess of EPROMs of various sizes, and I've successfully used them to build cartridges for the Atari 7800, the TI 99/4A, the 400/800, and the 2600 (4K non-bankswitched). I'd like to build myself some repros of 8K and 16K 2600 games next. I've got a couple PCBs and bankswitch logic chips from Pixels Past and from AtariService.com, but for the life of me, I can't get a single 8K or 16K 2600 game working with any of these boards.

 

Is it as simple as burning a copy of the game (the ones that are available for download on AtariAge) to a 2764 or 27128 EPROM and plugging it into the board, or does the binary need to be modified first? Also, which way are the capacitors supposed to be installed? I tend to get tiny ceramic axial capacitors with the boards and I can't figure out which way is which (if indeed it matters). Those are the only two potential problems I can think of; the boards didn't come with instructions, but it wasn't hard to figure out where all the components go, and I can't see anything wrong with my soldering.

 

I figure it's got to be something I'm doing wrong, but what?

[CPUWIZ]

What game(s) did you try? The caps and resistor are not polarized, it doesn't matter which way they go. You can not, however, switch C1 for C2, they have different values.

[jaybird3rd]

So far, I've tried Track and Field, the F6-modified version of QBert's Qubes, and Combat II. I'm also going to try Save Mary and Klax, but I'm waiting until I figure out what the problem is because I don't want to waste a SARA chip.

 

Thanks also for the info about the capacitors; I knew resistors are not polarized, but I wasn't sure if the capacitors were. Also, I guess I should have said that I'm comparing my EPROMs to the original binaries after I burn them, so I'm pretty certain my chips are good.

Edited November 4, 2006 by jaybird3rd

[CPUWIZ]

Hmm, those should all work, you did not switch the 101 and 104 cap, right?

[jaybird3rd]

Hmm, those should all work, you did not switch the 101 and 104 cap, right?

I've just checked the Parker Brothers board I'm using for testing. As it's currently wired, C1 (the yellow 101) is in the upper-left corner by the PLD, and C2 (the cyan 104) is on the underside by the resistor. The PLD's pin 1 is on the lefthand side of the board and the EPROM's pin 1 is on the righthand side, according to the silkscreen layout. I've socketed the EPROM for testing and am currently using a 27C128 with the F6 version of QBert's Qubes.

 

Here's what's happening when I try it (in my 7800): I'm getting gray diagonal lines that scroll up and down on the screen.

Edited November 5, 2006 by jaybird3rd

[CPUWIZ]

You swapped them, the cyan one should be by the PLD, makes perfect sense that it doesn't work.

[jaybird3rd]

You swapped them, the cyan one should be by the PLD, makes perfect sense that it doesn't work.

Aha, I knew it had to be something simple. I used the cyan cap in the "C2" slot because the bag they were in was labeled "C2." Shouldn't be a big deal to exchange them, though. I'll check in later with my results. Edited November 5, 2006 by jaybird3rd

[CPUWIZ]

You swapped them, the cyan one should be by the PLD, makes perfect sense that it doesn't work.

Aha, I knew it had to be something simple. Funny, the bag of cyan caps was labeled "C2," so that's where I put them.

 

Crap, my bad then, make sure to send me an email next time you get something from the website and I'll send you a discount coupon.

 

Sorry about that, I packed up your package late at night, after working 11 hours and spending 2 in traffic. Wanted to make sure you get your package fast.

[jaybird3rd]

Crap, my bad then, make sure to send me an email next time you get something from the website and I'll send you a discount coupon.

 

Sorry about that, I packed up your package late at night, after working 11 hours and spending 2 in traffic. Wanted to make sure you get your package fast.

No problem at all ... I appreciate your getting the order out so quickly. I swapped the capacitors and everything worked perfectly.

 

I'm actually glad it happened this way, because I also have a batch of Pixels Past boards from AtariAge that are showing the same symptoms. Those have been puzzling me for months (I was afraid the PLDs were blank or something), and now I know what to look for.

 

Thanks so much for all your help, and for making such a fine product. I am VERY pleasantly surprised by the quality of these boards, especially the 7800 boards. Now that I know that bankswitched 2600 carts will work for me, I'll definitely be buying more.