help with MMC1 repro

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chunk337
Posts: 3
Joined: Tue Apr 13, 2021 11:01 am

help with MMC1 repro

Post by chunk337 »

im trying to make a repro cart with a copy of operation wolf. The original CHR and PRG are 28pin 128k in size. The problem is when i try to fit the new EEPROMS in (27c010) the CHR will not physically fit without overlapping the PRG. How do i go about making the game? From what i understand you can not buy 128k chips that are 28 pin.
lidnariq
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Re: help with MMC1 repro

Post by lidnariq »

You're right, you cannot do the thing you want to do. You'll have to instead do one of the following:

* Add a carrier PCB and a surface mount ROM so that you can put a smaller ROM in that place
* A different carrier PCB like https://www.etsy.com/listing/826068839/ ... pter-board
* Use a different donor
* A ridiculous amount of rework
* Carefully ablate away the epoxy off one side of the lead frame for your ROM and do the rework there
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Fisher
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Joined: Sat Jul 04, 2015 9:58 am
Location: -29.794229 -55.795374

Re: help with MMC1 repro

Post by Fisher »

I had a similar problem and solved it by soldering the IC under the board like this:
20160801_160227.jpg
Since then, I've been using PLCC ICs, which normally don't give me these kinds of problems, but the end result is something like this:
6e6fc187-469c-4973-8907-d4290c137088.jpg
Of course, there are better, faster, and more sophisticated ways to solve these problems, but since I have some time to spare and little money to use I'm on "the cheap side of the force". :-D
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krzysiobal
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Re: help with MMC1 repro

Post by krzysiobal »

I made special adapter for that purposes (one side, so can be etched at home!):
Image Image Image Image Image Image
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chunk337
Posts: 3
Joined: Tue Apr 13, 2021 11:01 am

Re: help with MMC1 repro

Post by chunk337 »

lidnariq wrote: Tue Apr 13, 2021 6:12 pm You're right, you cannot do the thing you want to do. You'll have to instead do one of the following:

* Add a carrier PCB and a surface mount ROM so that you can put a smaller ROM in that place
* A different carrier PCB like https://www.etsy.com/listing/826068839/ ... pter-board
* Use a different donor
* A ridiculous amount of rework
* Carefully ablate away the epoxy off one side of the lead frame for your ROM and do the rework there
thank you i just ordered some of the adapters
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Fisher
Posts: 1249
Joined: Sat Jul 04, 2015 9:58 am
Location: -29.794229 -55.795374

Re: help with MMC1 repro

Post by Fisher »

krzysiobal wrote: Thu Apr 15, 2021 3:44 pm I made special adapter for that purposes (one side, so can be etched at home!):
Wow!
That's cool.
Thanks for sharing. :-)
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