Some carts work fine, some with glitched graphics, some dont

Hello,
I have a little problem with my NES, before posting I've been searching through the forums and haven't found any information on it.
First of all, I have experience in electronics and programming, but I'm just starting to get into the NES.
Some months ago I bought two NES front loader consoles on some flea markets. The consoles were lying in the ground between a load of other things, but they both seemed to be in a very good condition. I opened both of them and cleaned them carefully to remove all dust.
Then there was the flashing light problem. I unlocked one of the consoles cutting the pin in the motherboard (took care of not damaging anything else, the pin was disconnected clean).
One of the 72 pin connectors was really messed up, so I bought a blinking light win, and boiled the other connector / bended the pins carefully.
I've tried the blinking light win and the connector on both the consoles, but both seem to have some issues.
I will focus on the locked/untouched console, which is the one that I think works better.
I have several game cartridges that I have carefully opened, cleaned using the technique of pencil rubber / toilet paper with 96% vol alcohol. I've also done this on the motherboard, where you connect the 72pin/blinking light win.
After doing all this, the problem here is that SOME games show some glitched graphics. Some games doesn't even load, some load with glitched graphics and then freeze, and SOME play 100% well.
I will make a list of all the games that I have and their particular problems, this all is using the blinking light win:

Adventures in the Magic Kingdom: Just a black/grey screen
Bases Loaded: Works flawlessly
Castlevania 3: Just a green screen everytime
Chiller: Just a black/grey screen
Dragon Warrior: Most of the times a green (sometimes other colors) screen, sometimes a very glitched frozen intro screen
Duck Hunt: Most of the times a black screen, sometimes a very glitched intro frozen screen
Gauntlet (unlicensed): Works flawlessly
Golf: Most of the times a black screen, sometimes a very glitched intro frozen screen
Gyromite: Just a black/grey screen
Hogan's Alley: Most of the times a black screen, sometimes a very glitched intro frozen screen
Hoops: Most of the times a black screen, sometimes a very glitched intro frozen screen
Hydlide: Game starts but theres a frozen screen with some little glitched graphics. Sometimes you can even start playing with glitches but game freezes.
Ice Hockey: Just a black/grey screen
Kirby's Adventure: Sometimes a grey/cream screen, sometimes a glitched frozen intro screen, sometimes the game starts all glitched and freezes
Kung Fu: Just a black/grey screen
Little Nemo Dream Master: Most of the times theres just a black or grey screen, sometimes works with very glitched graphics
Mega Man 2: Works flawlessly
Mega Man 6: Works flawlessly
Pinball: Just a black/grey screen
Rad Racer: Sometimes game starts but graphics are pretty glitched, sometimes starts and freezes, sometimes doesnt even start
Super Mario Bros: Just a black/grey screen
Super Mario Bros/Duck Hunt: Most of the times a black screen, sometimes a very glitched intro frozen screen
Super Mario Bros 3: Works flawlessly
Super Spike V'Ball / Nintendo World Cup: Works flawlessly
Tennis: Starts but graphics are pretty glitched and then freezes
The Simpsons: Bart vs Space Mutants: Works flawlessly
The Simpsons: Bart vs the World: Works flawlessly

All the above are original games, I have also a 143 in 1 chinese cart that sometimes works, sometimes starts and then the picture gets glitched and freezes.
In this cartridge I tested several games, here's some examples of the behaviour:

Adventure Island 1: Works flawlessly
Adventure Island 2: Works flawlessly
Adventure Island 3: Works flawlessly most of the times but sometimes it just freezes when you begin.
Blades of Steel (that hack with southamerican teams): Works flawlessly
Castlevania 2: Starts well but when you begin the game the graphics are all glitched and game freezes
Ice Hockey: Works flawlessly
Kirbys Adventure: Plays but with very glitched graphics
Mighty Final Fight: Black screen
Super Mario Bros: Works flawlessly but this seems to be a pal version because it's speed up. Maybe a hack because in the intro screen you can't see the Super Mario Bros rectangle title.
Super Mario Bros 3: Frozen screen with the chess-intro-floor
Teenage Mutant Ninja Turtles 3: Starts but freezes before you start playing

I had the chance to test some of these games in other consoles and they worked well.
Also, some of the games seem to get messed up sometimes and without removing them by pressing reset or power off and on they work / i get the glitched graphics.
The behavior on this console is pretty much the same with the restored 72 pin connector.
The motherboard circuit looks really in good shape.

I have no clue how to even start looking for the problem.
Can anyone give me a hand on this?
Thanks in advance!

Could it be that some of the games are thrashed? I find it strange because the PCSs and all the components look excellent.

Could it be that the NES motherboard has something broken?

I tend to think that the connections are failing, but I have tried with 3 different 72 pin connectors, the two originals that I boiled / bended pins, one of these chinese low quality 72 pin replacements, and the blinking light win from arcadeworks... So now Iam at a point that I tend to think that there's actually something failing inside the NES.

Could it be that I'm using a generic power brick to power the NES? its 9v DC 850mA. I think it's good enough?

Any ideas where can I start looking?

Pictures of the glitched graphics can sometimes suggest a particular signal problem.

I've never heard of using toilet paper. I usually use a pencil eraser and paper towels with alcohol.

The list of games you have makes me think it's a problem with the cartridges. I say that because I don't really see any theme that makes sense. You have many NROM games failing yet more complex games like Mega Man 6 and Super Mario Bros 3 work without issue. Then Kirby's Adventure has issues which breaks that mold being a newer more complex game.

Maybe post pictures of the Kirby PCB's contacts. How clean are they and any signs of damage.

Thanks for replying.

I agree with you, with the list i've given it's really hard to find a pattern. It's not making much sense.
I have seen some video of someone finding some broken contact in some cart and wiring the game to fix it. If this is the case I will have a lot of work to do.

The strange thing is that the chinese 143 in 1 cart I have is brand new. Even if its pirate contacts seem to be in a perfect shape.

EDIT: Oh yes, I meant these paper towels you use in the kitchen (on the pictures), not toilet paper.

Here's another PCB.

I bought SMB3 and Super Spike VBall from some really dirty flea market. The carts were really dirty, cleaned them well, and the contacts on the pcbs even had some signs of corrosion. But the games work well.
The Kirby's Adventure cart I've had it for at least 20 years, bought it from a videoclub back then, and played really well on a pirate console I had back in the day. Didn't play it for maybe 10 years, and it was stored well with my Mega Man 2 and 6 carts which played flawlessly even without cleaning them.

This is the PCB of the new pirate 143 in 1 cart that also behaves weird as I mention on the previous posts.

the problem is SOLVED but please pay attention because this is really interesting.

i purchased a SNES on a flea market which came with a really nice 9v DC 1A power brick, not nintendo original, but good quality.
randomly i decided to test it on my nes console which behaviour i described in the previous posts. as i've said there, i used a 9v DC 850mA generic power brick.

i picked randomly dragon warrior and when i started the nes with the new power brick i noticed something weird. it was flawless! now all the games i described before work perfectly, 100x100, no glitches, flawlessly.

im completely surprised with this, since the nes says it should be used with 9v AC 850 mA... it should be the same with the one i was using..

i believe all this is a failing power brick that supplies lower amperage or voltage, and the nes was starving. mostly on games with bigger circuitboards like kirby's adventure and castlevania 3.

anyone knows anything about this? i find it pretty interesting.

EDIT:


ANOTHER fact I didn't mention:

this days between my posts i managed to make super mario bros / duck hunt run with small graphic glitches. the zapper gun was shooting but i could never hit a duck. now the thing works flawlessly as well.

Some cartridges do draw more power and that can always cause weird problems when you are on the edge. I actually had a 3rd party SNES Power Adapter I used for years and never noticed any issue until using InfiniteNESLives' SNES flash boards. Games would randomly reset/black out. After getting an official Nintendo power adapter for SNES the problems totally disappeared. So low quality or failing power bricks can certainly cause issues.

Take look how for many amps are rated rectifying diodes/graetz bridge in NES because when you supply NES with DC power supply, two diodes conduct current for the whole time and the other two don't so as a result - twice as much power is dispensed on them.