Issues with cic on opentendo

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Wyatt150
Posts: 7
Joined: Fri Aug 26, 2022 2:27 pm

Issues with cic on opentendo

Post by Wyatt150 »

I had 3 bad nes boards and after hours upon hours of troubleshooting I decided to buy an opentendo and assemble it. All went well until I tested it, I got a grey screen and no power light, after some screwing around I resocketed the 74hcu04ap chip and found that the ppu I was using was bad and it started working and read games, that is if it turned on, for some reason to get it to power on fully I have to screw with the power button otherwise I get just the grey screen and no video. The first thing I did was just jump the two power pins to make sure the switch wasn't dirty, and it wasn't, this did nothing. I screwed around with it for a while, I have socketed all the chips so I was testing my 3 nes's worth of them and the whole time I had to click the power button a bunch to get it to power on, when I got to testing all 3 of my cic's I tried to power it on with no cic and it powered on immediately every time, granted it was just a blue screen. It didn't seem to matter if I used a cic without pin 4 or with pin 4, it acted the same. I'm done screwing with it for the time being but my idea's so far are double checking all the caps because it seems to turn on less with a game genie in the mix leading me to guess a lack of power, I'm going to try to bypass the 7805 and temporarily power it through usb, possibly replace the 7805 because it outputs 4.93v rather than 5, I don't that's an issue but you never know, and finally I'm going to find a way to clean off the excess flux off the board, I don't have a way to do it other than use an old toothbrush and rubbing alcohol but that just spread it around evenly rather than having it focused where I soldered. It should be noted I used pretty much all of the passive components from my 3 dead boards if you think something specifically is bad let me know so I can replace it.
lidnariq
Posts: 11432
Joined: Sun Apr 13, 2008 11:12 am

Re: Issues with cic on opentendo

Post by lidnariq »

By far, the most likely thing to go wrong in a NES is the terrible ZIF socket. Have you cleaned it?

After that, the most likely failure is the RAMs.

4.93V is just fine. Anything 4-5.5V works.
Wyatt150
Posts: 7
Joined: Fri Aug 26, 2022 2:27 pm

Re: Issues with cic on opentendo

Post by Wyatt150 »

lidnariq wrote: Fri Aug 26, 2022 5:40 pm By far, the most likely thing to go wrong in a NES is the terrible ZIF socket. Have you cleaned it?

After that, the most likely failure is the RAMs.

4.93V is just fine. Anything 4-5.5V works.
The issue is most definitely not the zif socket, when it actually starts it plays the game perfectly, not only that but I converted to a normal cartridge connector using a game genie socket so we can rule out the 72 pin, like I said the issue is with the console not powering on most of the time. I can also rule out the ram chips because I tried two different sets of them and the behavior didn't change.
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aquasnake
Posts: 515
Joined: Fri Sep 13, 2019 11:22 pm

Re: Issues with cic on opentendo

Post by aquasnake »

7805 has two current output specifications, one is 1A and the other is 500mA. If 500mA is used, the output driving strength is insufficient and the voltage decreases.

In addition, a diode is connected in series at the GND pin of 7805, which can simply increase the output voltage
Wyatt150
Posts: 7
Joined: Fri Aug 26, 2022 2:27 pm

Re: Issues with cic on opentendo

Post by Wyatt150 »

Well I said I was going to take a break but I didn't...
It turns out there was likely something wrong with one of the circuits that connects to the CIC, however I have no clue which one. Using a combination of a few of the schematics in this thread viewtopic.php?t=9260 and some experimentation I got it to work 100% of the time by removing the CIC all together and bypassing using the schematics in that thread. If anyone is wondering how I did it I removed X2 and R1 and obviously the CIC, then put a 100k ohm resistor in the two open holes furthest away from the power box in the place of X2, I put on two jumper wires, one from the closer hole to the power box where R1 used to be to pin 9 where the CIC used to be, the other jumper being at the farthest hole from the power box at X2 to a pin 7 at the CIC, then I have a .1uf capacitor going from pin 4 of the absent CIC to closer pin to the power box of C7 which should be absent already, and finally I have another 100k ohm resistor going from pin 6 to pin 10 of the absent CIC that supposedly helps with compatibility and protecting it from CIC stun circuits.
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