How to fix a NES mainboard without 10NES lockout chip ?

[satchsatch33]

Hello friends,

I tried recently to disable n°4 pin of the NES10 lockout chip on my NES, but unfortunately, I destroyed the entire chip (now I have completely remove it).

Since I've done it, my NES does'nt boot on game cartridges (and seems it doesn't work when I turn it on, because It makes a permanent white screen), but I noticed something interesting : when I hit the n°9 pin point with the tip of my multimeter, it works !!!!! So I guess that my motherboard is not completely destroyed (sorry for my bad english). I noticed another problem : since I Have removed the 3195A chip, reset button doesn't work (only with this motherboard).

Do you recommend me to extract a 10NES chip from a game cartridge and just try to solder it to the mainboard, or maybe is there any other issue ?

Someone from a forum recommend me this :
"Hi,
I'm not as familiar with the CIC chip as some other folks on the Nesdev forums, but you might try using a 10k resistor to connect pin 9 to GND.
If that doesn't work, try searching the Nesdev forum for CIC chip removal. Worst case just start a new thread and someone can point you in the right direction.
Good luck!"

[MottZilla]

Yes you could use a CIC from an old game cartridge. Or you could try hitting the reset button after powering the system on. Or you could do this modification. viewtopic.php?f=9&t=9244#p98535

[satchsatch33]

Thank you so much for your answer, but it's difficult to see on this photo what he exactly did.

Anyone to explain ?

Thx

[lidnariq]

You could just solder a 100k resistor from ground to pin 9, but the reset button won't work.

The step-by-step guide was linked from that post, but here it is again: viewtopic.php?p=39814#p39814

[lidnariq]

And here's a little cartoon of it:

cicremove.png (5.63 KiB) Viewed 13735 times

[satchsatch33]

For the soldering of 100K resistor, I have to remove the little blue blue plastic protection ?

[lidnariq]

Yeah, you'll need to have removed U10, R1, and X2. (And C6 and C7 if they exist, but they probably don't)

[satchsatch33]

Thanks.
Do I need to disolder the 1M resistor ?
Do I have to solder the "-" or "+" on the n°4 pin ?

[lidnariq]

You probably don't have to desolder the 1Mohm resistor, but I would; I specifically chose the wiring I did to take advantage of preexisting solder holes.

Where'd you find a polarized 0.1µF capacitor? The capacitor will be charged to +5V whenever reset isn't pressed, and briefly exposed to -5V when power is turned off, so it'd be best to use a non-electrolytic.

If you have to use a polarized one (and make sure you don't have a 1µF cap), the +ve side should be CIC pin 4, but you should expect it to spontaneously fail randomly about 5 years in the future.

[jims cool]

this is how i do it!



everything works as if it never had one in the first place
you should remove the CIC protection diodes or some games with the -5v spike circuit might get confused

also works with copynes

had this file for years just never had webspace lol

[satchsatch33]

It seems that your schematic is so different than linadriq's.....

[jims cool]

my schematic uses an inverter from the oscillator to protect the CPU/PPU and also turns the power light off when you hit the reset button

the two extras inverters go to ground so they aren't floating because that's bad

also disconnects the inverter that goes to the CIC/-5v zap circuits in game packs.. normally a clock but without the oscillator its floating between +5 and ground also very bad

the only way you can tell that it's been modified is it doesn't flash without a game in the console
because that's the cic's job... it's basically a perfect board patch circuit

the capacitor can be anything below 10uf and above 0.1uf.. but i would go with 10uf gives you a good solid reset with no noticeable delay... should be between 10v and 50v

i tried the pin 4 thing back in the day thinking it would be a cool hack.. the truth is when the cic is in key mode the lockout pin is stuck in reset..that's how it was coded.. tapping reset with pin 4 floating can get it to work but nes has enough problems

[satchsatch33]

Thank you so much, but I'm a true begginer in electronic stuff....

Is there any other issue, for example if I only want use it without reset function ?

Linnariq suggest to solder a 100k resistor from ground to pin 9, but the reset button won't work (where is situated ground ?)

[jims cool]

i think that circuit would zap pin 2 of U9

pin 2 of U9 is output it's tied to pin 3 and 13 inputs. pin 4 is connected to the clock input of the CIC or -5v zapper circuit.. so it could be bad for some games

if you don't want reset just switch the cap a resistor around and instead of the center connection being pinhole 7 (the reset switch) connect the center connection to pin 9 cpu/ppu
and your good to go

if you play games like the legend of zelda with memory you will most likly need to keep the nes on so keep your game saves..

[lidnariq]

There is absolutely nothing wrong with my design. The difference is that my design doesn't involve lifting pins of the inverter.
The only huge difference is that jims cool's design uses the inverter on pins 13-12, and mine uses the inverter on pins 1-2.