I had some major issues finding an AC adapter that would work with a stock NES, so I modded mine to run off batteries. I've also got tired of feeding my NES batteries, so I got an AC adapter that would plug into the battery clip I was using. It worked, but it had the weird graphics thing, it rendered correctly, but had a weakly colored band scrolling down the screen, followed by a strongly colored band. Thinking I didn't have enough voltage going to the NES, I turned it off, flipped the selector over one notch, and turned it back on. Grey screen. Flipped it back, grey screen. Plugged in batteries, grey screen. Different game, grey screen. My games are all clean, and I put a new 72-pin connector in. They used to even work if I didn't press the cartridge holder down, too. Any idea if it's saveable, or do I need to look for another NES off ebay?
Did you have the power adaptor connected before or after the 7805 voltage regulator (the thing with a big aluminum heat sink)? If you had it connected after, the band was probably due to the voltage having too much ripple (i.e. unregulated), since most wall transformers don't do any regulation. If you had it connected before the regulator, then you shouldn't have damaged anything.
I completely took the RF box off, and I couldn't get it open when I was working on it, so the regulator is disconnected. That whole thing is somewhere in my toolbox ATM.
Did you hook it up right?
(5V is towards the pcb edge while video is towards the cartridge connector)
Edit: and reading more it's possible that you fried the nes with too much voltage.
I'm thinking I did give it too much voltage. I'm just not sure which part, since on my other NES, a steady grey screen shows if the cartridge isn't plugged in, and I've tried a few different carts in the bad one. I definately have it hooked up correctly, though, since it was working perfectly before I tried the adapter.
I did some googling about the 7805, and using it seems like I'd need to run at least 7V through it for it to work properly, and it'll increase power consumption by around 20-25%, which isn't very helpful at all when using batteries. It was working perfectly with 4xAAs, and I had it wired up so it would use the original power switch.
This is kinda OT, but if I have the tip polarity set right, can I use a plain 9VDC adapter inplace of the original 9VAC the NES used?
shadowzero313 wrote:
This is kinda OT, but if I have the tip polarity set right, can I use a plain 9VDC adapter inplace of the original 9VAC the NES used?
Since the NES takes 9VAC, I believe you can give it DC in
either polarity and it'll work fine (since it'll just run it through a rectifier anyways).
I probably should've figured that out before I started on my battery scheme. Oh well, electronic stuff is fun to play with. I've still got a working NES, at least.
For the second version of my NES mod, I want to be able to switch between a wall adapter and a AC -> DC adapter. The thing I'm stuck on with this plan, though, is everything I have that will run off both, mainly cd players, all shutdown when I switch power sources. Since that's very unreasonable for a long NES session, especially with no saving in most games, I'm trying to figure out how to get it to run from the batteries only if the AC adapter isn't plugged in, otherwise it stops using the batteries, but keep it seeming like nothing happened to the NES. I think I can use a capacitor in between the NES and the battery pack/DC plug, but I'm not sure how to keep the batteries from draining, or worse, being charged from the wall. Any ideas for that?
Yes, you can use either polarity DC, or AC.
Just make sure that you use at least 9VDC 500mA.
The bridge rectifier knocks off .6V which drops your 9V down to 8.3, barely 3V above the regulator. Most 5V regulators need at least 7V of DC, with the ripple riding above the 7V (or else you get drop out).
drk421 wrote:
Yes, you can use either polarity DC, or AC.
Just make sure that you use at least 9VDC 500mA.
The bridge rectifier knocks off .6V which drops your 9V down to 8.3, barely 3V above the regulator. Most 5V regulators need at least 7V of DC, with the ripple riding above the 7V (or else you get drop out).
Actually, the bridge knocks off a bit over 1.2V, since you're running through two diodes in it.
As for the original poster, I think the NES is toast, if it got more than 6V or so the chips won't like it too much. If you want to run the NES on batteries, you should be able to make a really efficient step down converter using some chips from maxim (
www.maxim-ic.com), netting at least 90-95% efficiency. These will get the maximum life out of the batteries and as a bonus, it won't even get warm while it's doing it.