lockout chip removal

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sleepy9090
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Joined: Fri Aug 22, 2008 10:04 am

lockout chip removal

Post by sleepy9090 » Fri Oct 24, 2008 8:12 pm

so i have a couple systems i disabled lockout chip on with the pin 4 trick and they work fine

I have one system that the lockout chip is damaged, i do not want to remove one from a cart to fix it

1.Can someone show me a way to make a system work without the lockout chip. Just completely bypass it. If the new top loaders do not have them then the wiring should be possible. (i read the forum and did not see this questions posted already but if it has please excuse me)

2.I am going to use this system if i get it going for a dev unit. If i am not successful what system would be recommended? top loader?

thanks all

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Bregalad
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Post by Bregalad » Sat Oct 25, 2008 1:00 am

1.Can someone show me a way to make a system work without the lockout chip. Just completely bypass it. If the new top loaders do not have them then the wiring should be possible. (i read the forum and did not see this questions posted already but if it has please excuse me)
You probably want to tie reset in directly to reset out and that should work. I'm not exactly sure tough.
Useless, lumbering half-wits don't scare us.

drk421
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Post by drk421 » Sun Nov 02, 2008 4:01 pm

1) You need to remove the lockout chip.
2) Put a 1uf capacitor between ground and reset
3) Run a wire to the reset button so it grounds reset when pushed.

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sleepy9090
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Post by sleepy9090 » Mon Nov 03, 2008 11:35 am

exactly what i was looking for
thank you

lidnariq
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Post by lidnariq » Sun Nov 09, 2008 6:00 pm

I came up with a design that won't require cutting a trace and soldering a flying wire to the front power PCB:

Since the 4MHz resonator is only used for the CIC (although it's exported to the cartridge, I don't know of any carts that use it for anything else), i figured I could get away with repurposing its driver (the adjacent 74HCU04) to invert the logic from the reset button.

Orient the board such that these labels are upright, near the CIC: "R1" "1M" "C6" "C7" "X2".

* Remove the CIC, the adjacent 1Mohm resistor (R1), and the 4MHz resonator (X2).
* Solder a jumper from CIC socket pin 7 (Reset in, +ve logic) to the hole the 1M resistor was in below CIC pin 9 (the right side)
* Populate the missing capacitor C7 (0.1uF), but not to ground -- instead connect the right side to +5V (CIC pins 4 or 16) -- see footnote.
* Replace the right half of the crystal w/ a 100kOhm resistor (middle to pin #3, as labeled)
* Jumper from the left side of the resistor (below CIC pin 8) to CIC socket pin 9 (/Reset out, -ve logic).

I originally tried just populating C7 w/ a capacitor to ground. But the CPU wouldn't run after a cold boot, presumably because /Reset became true to early -- so it seems the CIC served as a power-on delay in addition to its protection functionality.

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