Need to make a cheap controller test cart...

[CZroe]

I’ve got a few projects going on for my Atari 5200 where it would be really useful (almost necessary) to have a controller test cart. I have a dead copy of Ms. Pac-Man that I’d like to convert. I recall reading long time ago that replacing the EPROMs directly wouldn’t work because the CE pin or OE pin was inverted or something compared to how it operates on most EPROMs.

 

Is this documented anywhere? How do homebrews get around this? Does a guide for doing this already exist? Thanks!

[smbaker]

I seem to have something laying around for everything these days. This is something I built after I first got my 5200:

 

 

This uses a 39SF040 512K flash rom, and the rotary switch lets me choose any of 16 images. Note that I soldered the flash chip (after programming it) in this case as I was trying to make it fit "inside" the cartridge shell. This was kinda dumb, and made reprogramming impossible. I ended up making a new one with a socket, and cut out the front of the shell to accommodate the height of socket+IC.

 

I assume the homebrew guys use some atarimax-style devices, as that would be relatively easy. Personally, if I ever do a homebrew (doubtful, time limitations) then I'd probably use my pi-powered multicart, as it has Wifi and I can load new images right into it.

 

Scott

Edited September 24, 2018 by smbaker

[CZroe]

I seem to have something laying around for everything these days. This is something I built after I first got my 5200:

 

5200-16n1-cart.jpg

 

This uses a 39SF040 512K flash rom, and the rotary switch lets me choose any of 16 images. Note that I soldered the flash chip (after programming it) in this case as I was trying to make it fit "inside" the cartridge shell. This was kinda dumb, and made reprogramming impossible. I ended up making a new one with a socket, and cut out the front of the shell to accommodate the height of socket+IC.

 

I assume the homebrew guys use some atarimax-style devices, as that would be relatively easy. Personally, if I ever do a homebrew (doubtful, time limitations) then I'd probably use my pi-powered multicart, as it has Wifi and I can load new images right into it.

 

Scott

Nice! Just got finished watching your rPi0w video and I’m really tempted to try it even though I know I’ll spend enough effort that it makes more sense to just buy the $130 SD cart. [emoji4]

 

For socketing DIPs with low clearances, here’s a little something I found from the Neo Geo Dev guys where the socketed ROMs have to fit between two boards with a low clearance dictated by the cartridge slot:

These are Mil-Max “Pin Receptacles.” They aren’t cheap since you pay per-pin but they add negligible Z-height to a typical SIP/DIP. Heck, you can probably eliminate even that little bit by bending the pins.

 

Can you even tell that the DIP40 on the bottom has these things capping each leg? [emoji6] Best price I could find was at Allied Electronics.

Edited September 24, 2018 by CZroe

[smbaker]

Nice! Do you have a part number / link to these pin receptacles?

 

Scott

[CZroe]

Nice! Do you have a part number / link to these pin receptacles?

 

Scott

Dug up my invoice and it looks like I ordered these:

https://www.alliedelec.com/mill-max-0548-0-15-01-11-27-10-0/70249715/

Edited September 24, 2018 by CZroe

[Shawn]

Those are really cool but very pricey.

[Shawn]

If you just need someone to burn you a copy of Pete's Test Cart I can do that for you.

[CZroe]

Those are really cool but very pricey.

Yeah. I wouldn’t use them just anywhere I might consider a socket but it’s good for clearance issues where a socket would be a deal-breaker. When K first heard of them I calculated that a fully populated Neo Geo board was going to cost hundreds at the prices I was seeing! Luckily, you only need them on one of the two boards if you go without a case.

 

If you just need someone to burn you a copy of Pete's Test Cart I can do that for you.

Thanks, but I can probably program the ROM if I knew what chip was a drop-in replacement. Thing is, I recall someone telling me that there were no drop-in replacements and that I would need something to invert the chip select or enable lines or something... hence this thread where I was hoping to get that info again.

 

I think I found a workable alternative by just using Missile Command for testing. I realized that it isn’t a matter of just blindly choosing a capacitor value that allows me to reach the right edge since I can also see what value puts my cursor at the center of the screen with the stick at center of the controller. Of course, I’m only adjusting for the horizontal axis but both pots degraded equally and this should be good enough.

 

Your suggestion in the other thread of starting at 10nF and adjusting from there was right on the money. 10nF almost restores the pot range and very nearly reaches the right edge.

15nF reaches the right edge and puts the center position very near the center in-game.

20nF feels the same but the game’s cursor is a little further away from center when the stick is centered, making it clearly less-optimal.

 

15nF it is! Maybe I should try to get a kit with more granularity in the 10-20nF range so I could really dial it in but the cursor is pretty close to center and it seems to work perfectly now. Only reason for a test cart at this point would be to confirm that I’m getting similar values to an original stick... but I’m pretty sure I am.

 

This kit had 50 values between 1pF and 100nF but only 15 values in the nF range and none between 10nF and 15nF despite a 50% capacitance jump.

[Shawn]

Yeah. I wouldn’t use them just anywhere I might consider a socket but it’s good for clearance issues where a socket would be a deal-breaker. When K first heard of them I calculated that a fully populated Neo Geo board was going to cost hundreds at the prices I was seeing! Luckily, you only need them on one of the two boards if you go without a case.

 

Thanks, but I can probably program the ROM if I knew what chip was a drop-in replacement. Thing is, I recall someone telling me that there were no drop-in replacements and that I would need something to invert the chip select or enable lines or something... hence this thread where I was hoping to get that info again.

 

I think I found a workable alternative by just using Missile Command for testing. I realized that it isn’t a matter of just blindly choosing a capacitor value that allows me to reach the right edge since I can also see what value puts my cursor at the center of the screen with the stick at center of the controller. Of course, I’m only adjusting for the horizontal axis but both pots degraded equally and this should be good enough.

 

 

Yes there is no drop in replacements on retail carts. A half dozen different commons you can use with an eprom but you have to do a little rewiring and add a 74ls08.

 

[CZroe]

 

Yes there is no drop in replacements on retail carts. A half dozen different commons you can use with an eprom but you have to do a little rewiring and add a 74ls08.

 

5200 pcb.png

Thanks! This is exactly what I needed.

 

FYI, I accidentally transitioned from talking to you to talking to smbaker in my last message without quoting him. Oops! He was the one suggesting a range of capacitor values to try for restoring a brand-new CX-52 with bad pots.

[Shawn]

Thanks! This is exactly what I needed.

 

FYI, I accidentally transitioned from talking to you to talking to smbaker in my last message without quoting him. Oops! He was the one suggesting a range of capacitor values to try for restoring a brand-new CX-52 with bad pots.

 

I caught on to that. It's all good.