This is my first time posting on this forum. Hopefully I can get some advice on where to look first.
I modded my NES to bypass the CIC chip (pin 4 to GND). I also recapped it because it is doing something funny. When I power it on, it works for about 5 seconds, then the power light goes out and the screen goes black. It will not work anymore until I let it sit for a while (discharging caps?).
I also have a 2nd system that works to compare it to but I don't know what to look at.
You're overheating the 5V regulator. The NES won't turn back on until the regulator is cool enough again.
You've probably got an ≈5 ohm short between 5V and ground. (You should see closer to 250 ohms)
That makes sense. I'll check it tonight and post the results. Thanks!
OK, I am getting about 340-400 ohms when it is cool. So I guess this becomes a general newbie electronics question about how to find voltage leaks. Can someone point me in the right direction? Thanks again!!
Hm. So you modified the CIC pin 4 and recapped the NES ...
Does the 7805 (as I suggested) get hot? Just making sure.
You can
pull the CIC altogether and still have a functioning NES, or you seem to be able to
repurpose the CIC's crystal oscillator and get something functional too.
Can you show pictures? I hope you lifted pin 4 and didn't just directly connect it to GND... You can also just lift it, and not connect it to anything (there's supposedly a pulldown to ground within the IC).
I like that Hong Kong CIC mod. I will just remove the chip because pin 4 is kind of tweaked. Maybe I damaged a VIA when pulling it out.
I tried to feel the 7805 but my fingers are not very sensitive to heat anymore. I could just replace that too. I'll keep you posted.
Thanks everyone for your prompt replies. This is an awesome forum! You guys are master hackers!!
Ok, I just removed the CIC chip and ran jumpers from CIC pads to the C7, etc... and it's working now. Must have been that pin 4 VIA shorting or something.
So it looks like the downside is no reset button, but you could probably just rewire that from the power wire. So just to throw out discussion, why even mess with the CIC chip and cloning it and all that? Seems pointless to me. Desolder that bitch and throw it in the trash! I dont think it takes any less skill to remove it than to cut one of the pins for a newbie. And leave everything around it intact.
The picture I showed you of mine
should work with the reset button. If it's not, you've got something else wrong. (Also
see my symbolic version, which despite what I said there, I
have since tested)
The reason behind cloning the CIC was the nicety of not making the end user modify their console.