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PostPosted: Sat Jul 09, 2016 1:23 pm 
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Hi All!

This is my second repro. I did Mega Man last week and everything went great! I just finished Metroid last night (donor from 720), and am having some issues with it.

First off, on the title screen, there is a floating square in the middle and blinks and moves a little, similar to the selector from the next screen (after you hit Start). After you hit Start, then hit Start again to start the game, it shows this glitchy blue screen and then after about 5 seconds, the game restarts back to the title screen. I am using a ST M27C1001, which I did view the data sheet for and matched it to the pinout of the MMC1 board (720 is actually a MMC1B2, but apparently they are nearly identical). When I received the donor cart, some of the contacts on the cart were a little corroded, but I think I cleaned them up enough. I also have tested all of the traces with my multimeter and none of them seem to be broken.


Thanks for all of your help! I'm getting a kick out of all this soldering and 'intro to electronics'!!!!


Attachments:
File comment: Top view
Pin 2 to hole 24
Pin 16 to pin 24
Pin 1, 30, and 31 not connected, 1 is program supply, 30 is NC (not connected), 31 is Program.

IMG_20160709_131145.jpg
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File comment: Beginning of the game, after the 'Start or Continue' screen
IMG_20160709_125217.jpg
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File comment: Title screen with flashing square in the middle
IMG_20160709_125202.jpg
IMG_20160709_125202.jpg [ 876.32 KiB | Viewed 3149 times ]
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PostPosted: Sat Jul 09, 2016 1:49 pm 
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Location: Tampere, Finland
Metroid requires 8 KB WRAM on cart.

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PostPosted: Sun Jul 10, 2016 5:54 pm 
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Joined: Sat Jul 09, 2016 12:54 pm
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Any chance that is diy-able, or do I simply need a new cart? Can you recommend one (or recommend a list for reference)?

I would check bootgod, but it has been down for the past couple weeks.

Thanks!


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PostPosted: Sun Jul 10, 2016 6:06 pm 
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Location: Canada
The wiki has some instructions about adding WRAM to a cartridge, though I'm not sure if it applies to MMC1 or not.
http://wiki.nesdev.com/w/index.php/PRG_RAM_circuit


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PostPosted: Sun Jul 10, 2016 6:23 pm 
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Location: NE Indiana, USA (NTSC)
That page is mostly about generating a chip enable for WRAM by decoding $6000-$7FFF. The MMC1 already generates that signal.

Converting SGROM to SNROM without battery needs a 6264 or compatible 8Kx8 RAM. Correct me if I'm wrong, but from the pinouts of MMC1, 6264, and ROM, it goes like this:

  • 6264 GND (14) and /OE (22) to ground
  • 6264 power (28) to +5 V
  • 6264 A12-A0 and D7-D0 to the corresponding ROM pins
  • 6264 +CE (26) to MMC1 WRAM +CE (6)
  • 6264 /CE (20) to MMC1 CHR A16 (11)

If you have a 62256 instead of a 6264, it won't have a positive chip enable (+CE), just a negative one (/CE). You will need to add an inverter to turn WRAM +CE into a /CE signal.

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PostPosted: Sun Jul 10, 2016 6:39 pm 
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Joined: Sat Jul 09, 2016 12:54 pm
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You guys are quick! I'm really starting to like this forum!


I will look for a for-sure pinout and see if I can get that ordered and soldered up! You guys rock!!!


Thanks again!!!


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PostPosted: Mon Jul 18, 2016 12:27 am 
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Joined: Sat Jul 09, 2016 12:54 pm
Posts: 6
So I have made some progress... I got a Hitachi 6264 chip and got it all wired up, unfortunately, it's still glitched, but atleast I get some letters this time...

I'm using roughly 30guage wires, except for the power and ground wires. Any thoughts?


Attachments:
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PostPosted: Mon Jul 18, 2016 10:32 am 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
It looks like RAM pin 27 isn't connected to anything? Only pin 1 (nc) needn't be.

Pin 27 is RAM /WR, and it should be connected to NES CPU R/W (it's present on the MMC1)


Last edited by lidnariq on Mon Jul 18, 2016 10:46 am, edited 1 time in total.

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PostPosted: Mon Jul 18, 2016 10:45 am 
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Joined: Sat Jul 09, 2016 12:54 pm
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You're totally right! I initially had it soldered incorrectly, looked at the datasheet for the chip and the ROM and assumed it didn't need to be connected (thats what I get for assuming).

I will connect it and give it a shot

Thanks!!!


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PostPosted: Mon Jul 18, 2016 11:20 am 
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Joined: Sat Jul 09, 2016 12:54 pm
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You guys really know your stuff!

2 seconds of soldering later....


Attachments:
IMG_20160718_110711.jpg
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