Ressurected a TVROM game (p0rn included)

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Fisher
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Ressurected a TVROM game (p0rn included)

Post by Fisher » Sun Mar 25, 2018 4:12 pm

Sometime ago, I got some unfunctional games.
One of them was Rad Racer II.
So, I took a pirate Return to the Earth board and made a "transplant".
Here is the end result:
Component side
Component side
Solder side
Solder side
So far so good the game worked!!
In game
In game
This seems to be a problem with the original PCB, so I totally disassembled it and I'm sharing some board p0rn:
TVROM-Componentes
TVROM-Componentes
TVROM-Solda
TVROM-Solda
Since in other cases disassembly, clean and reassemble made the game work again, what chances I have that this happen again, this time with an original board?
Should I post the pictures on Bootgod's site?
Thanks in advance!!

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koitsu
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Re: Ressurected a TVROM game (p0rn included)

Post by koitsu » Sun Mar 25, 2018 4:50 pm

There's already an entry for Rad Racer II. The board type silkscreening (HVC-TVROM) on yours is identical to the one there pinout-wise, aside from some minor PCB differences (nothing major, seen this type of thing before). I don't know if BG's DB allows for raw (i.e. not populated with ICs/parts) PCB photos, but yours are higher res though.

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Fisher
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Re: Ressurected a TVROM game (p0rn included)

Post by Fisher » Sat Apr 07, 2018 6:09 pm

Now that you talked, I started to think a bit more.
It doesn't makes much sense to strip a well known board naked.
At least the well documented ones as this don't!

Other than curiosity there's no more valuable information to be gained from these.
But on pirate or unknown boards it does!
Specially if you don't want to miss any connection, wich is possible if you're with an exotic board and don't test all the possibilities.

At least the game is working and I have a nice board.
Probably it's a mapper IC problem, but I'll never be sure if I don't try to make a repro with this board.

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Bregalad
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Re: Ressurected a TVROM game (p0rn included)

Post by Bregalad » Sun Apr 08, 2018 5:33 am

Couldn't it be the electrolitic capacitor which got in short-circuit state ? Just a random educated guess.

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Fisher
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Re: Ressurected a TVROM game (p0rn included)

Post by Fisher » Mon Apr 09, 2018 6:15 pm

Nice tip! Thanks!
I've checked all the capacitors and even tested the board with them removed before stripping it.
I'll try to make a repro with it, maybe Megaman6...

I think a circuit to invert the PPU A13 is needed to be built, since this pin is missing on this board.
Originally the CIRAM /CE is pulled high, disabling internal PPU RAM, correct?
A simple inverter should do the job fine, maybe even a transistorised one.
A demux will be needed too, because I only have access to 2mb flash ICs right now.
I'll post the results as soon as I have a little more free time to do these stuff.

If I do everything correct and still get an non-functional game, probably it's the MMC3 that has gone.
Any place I can find a substitute that fits, if that's the case?
The Aliexpress' clones seems too big for this, but I think this can be worked around...

Or maybe I should try the "Holy diver Batman!" first.
I think Tepples renamed it, but right now I don't remember the new name... :oops:

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Re: Ressurected a TVROM game (p0rn included)

Post by Bavi_H » Mon Apr 09, 2018 6:45 pm

Fisher wrote:Or maybe I should try the "Holy diver Batman!" first.
I think Tepples renamed it, but right now I don't remember the new name... :oops:
Holy Mapperel (formerly Holy Diver Batman)

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Fisher
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Re: Ressurected a TVROM game (p0rn included)

Post by Fisher » Thu Apr 12, 2018 7:20 pm

Unfortunatelly I didn't tried the Holy Maperel first.
But I was lucky and everything just worked!!
I simply don't understand why...
But well, seems that the disassemble / clean / reassemble routine just worked!! :lol:

Here's some (badly taken) pictures:
de834022-f306-44d6-91c7-73a0d8f12544.jpeg
6be9e19b-d8c2-4ffd-a9c5-21a4f636a7b2.jpeg
The inverter circuit I used:

Code: Select all


                         +5V
                          | 
                          \
                          / 470R
             470pF        \
            +--||---+     +------ PPU /A13
            |       |    |/C
PPU A13 ----+--/\/\-+----| BC548
               10K       |\E
                          |
                          |
                         GND  
And the final result:
0220b19d-48fb-4bb7-9846-a76b8deb9fb1.jpeg
How could I improve the inverter? Is an improvement needed at all?
I was thinking in using some BF494/BF495, but I just didn't find one around.
So I used a BC548, wich I'm not sure if it's cutoff frequency is adequated / enough.
Could this became a source of problems in the near future?
Thanks in advance!!

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