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Problems with building Camerica Game Repro / Mapper 71
http://forums.nesdev.com/viewtopic.php?f=28&t=17712
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Author:  poggeldi [ Sun Aug 26, 2018 5:41 am ]
Post subject:  Problems with building Camerica Game Repro / Mapper 71

Hey you NES-Gurus! :-)
A friend of mine asked me to build a repro cart of the rare game "Dooly Bravo Land" (Korea only release).
Nestopia gives me the following information:
________________________________
Soft-patched: No
CRC: 86BE4746
SHA-1: 6AAA5521F91F101448E77C996C9802015578400C
System: NES-NTSC
Board: CAMERICA BF9093, Mapper 71
PRG-ROM: 256k
V-RAM: 8k
Solder Pad: H:1 V:0
Battery: No
Dump: Unknown
________________________________

As a donor cartridge i chose MIG-29/Camerica:
http://bootgod.dyndns.org:7777/profile.php?id=218
this should work i guess!?

I successfully built a good handful of repros in the past but have my problems with this one.
Do you have any hints how to rewire the PRG-EPROM?
Or is this Camerica-PCB a very special one that cannot be used as a donor?

Author:  poggeldi [ Fri Aug 31, 2018 7:18 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

no one who could help? :(

Author:  Fisher [ Fri Aug 31, 2018 7:30 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

Unfortunatelly I'm having personal problems and can't try some tests for now.
I'm sure someone else here can help to clarify things, even better than me.
Could you try your ROM on a UNROM board?
AFAIK the mappers are very similar, but not equal.

Author:  lidnariq [ Fri Aug 31, 2018 9:00 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

As far as we know, Mapper 71 is mostly just UOROM with bus conflict prevention and CIC defeat circuitry.

But I'm a little skeptical that a Korea-only release actually used that hardware.

Author:  krzysiobal [ Fri Aug 31, 2018 9:43 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

Dooly Bravo Land is just regular 256K UNROM (or rather UOROM) game, but it has bus conflicts and writes at $c000-$ffff to change PRG banks, that's why it was assigned mapper 71.

Mig29 Soviet Figher is 128K game and the BF90XX chip it uses has only 3 bits for storing bank number so it is not good donor candidate.

---

OK, Look's like in contrary to FireHawk (which is also 128K and uses BF9097), the version at bootgod uses BF9093 which has 4 bits, so maybe the line controlling PRG-A17 is not wired to anything and can be rewired to support your game.

---

If your version uses BF9093, chech to what is wired pin14 of that chip.

Author:  Fisher [ Fri Aug 31, 2018 3:06 pm ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

Could this be used on a mapper 180 board?

Author:  poggeldi [ Sun Sep 02, 2018 2:39 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

Thanks for your answers!

krzysiobal wrote:
If your version uses BF9093, chech to what is wired pin14 of that chip.


Yes, my version uses BF9093. Pin14 of that chip is not wired at all. Should this pin be wired to PRG-A17?
PRG-A17 (PIN 30 of the EPROM) is also NOT connected to anything on the board...

And is there any other pin which should be lifted/rewired?

Author:  krzysiobal [ Sun Sep 02, 2018 9:48 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

Quote:
Should this pin be wired to PRG-A17?

Yes, connect them.

Author:  poggeldi [ Thu Sep 06, 2018 8:09 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

krzysiobal wrote:
Quote:
Should this pin be wired to PRG-A17?

Yes, connect them.


Unfortunately I still get a grey screen (nothing displayed) when I connect those 2 pins...
Any other ideas?

Author:  krzysiobal [ Thu Sep 06, 2018 3:22 pm ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

What EEPROM or Flash are you using?

Author:  poggeldi [ Fri Sep 07, 2018 6:16 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

I use a WINBOND W27C020 EEPROM... Never had any problems with those.
But can I destroy an EEPROM by connecting something wrong?
I think my first rewiring attempt was this one:
Bend up pins 1, 2, 24 and 31
Solder pin 2 to hole 24 (A16)
Solder pin 24 to GND (OE)

Then I simply tried it without any rewiring (PRG-ROM=EEPROM 1:1) and your suggestion BF9093/Pin14->PRG-A17

Author:  krzysiobal [ Sat Sep 08, 2018 8:57 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

Check if EPROM.PIN1 is connected to VCC (if not, connect it)

Author:  poggeldi [ Fri Sep 21, 2018 5:39 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

Sorry for the late answer.
Yes, PIN1 is connected.
Please look at the fotos attached. Do you see anything wrong there?

---
edit: oh wait... PIN1 is VPP (only for programming the chip), right? this is not connected. PIN 32 is VCC...

Attachments:
20180920_074414_resized.jpg
20180920_074414_resized.jpg [ 1.85 MiB | Viewed 7310 times ]
20180920_074404_resized.jpg
20180920_074404_resized.jpg [ 1.74 MiB | Viewed 7310 times ]

Author:  lidnariq [ Fri Sep 21, 2018 9:04 am ]
Post subject:  Re: Problems with building Camerica Game Repro / Mapper 71

The W27C020 EEPROM datasheet doesn't say anything about what Vpp needs to be doing during read operation, but you probably still want to tie it to either +5V or 0V instead of letting it float.

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