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PostPosted: Sat Feb 24, 2018 8:06 am 
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A while back I gott a nonfunctioning Sonic 3, board only.
Although it was reasonably clean, i didn't boot.
While doing random tests, I tried it with a Mega Key, just like this one:
Attachment:
File comment: MegaKey
MegaKey.jpg
MegaKey.jpg [ 107.22 KiB | Viewed 1938 times ]

It showed a message telling it was designed to be played on NTSC systems.
So, I played a little with the switches and it booted fine with all of them off.
Interestingly it didn't boot alone even with a game genie.
I quickly opened it to see what's inside and I only could find an epoxy blob, the 4 switchs and some parts marked as RPx, wich I suppose are some resistors associated on a bar.

I also removed the FRAM and the logic circuits around it, routed the ROM /CE to the 74HC139 pin 1 and got the same results.
Is there anything I can try to do to make it boot alone?
It's also missing all the capacitors, except the electrolytic one.
What capacitors are these? I think they're decoupling capacitors, but I didn't find an clear enough image to see its values, would they be 100nF (104) ones?
Also, it's not saving, I fount that specific FRAM chip (FM1208S) to be expensive, maybe I could use an SRAM on its place.

Just in case someone is interested, here is some board p0rn:
Attachment:
File comment: Solda
Sonic 3 - Componentes - S.png
Sonic 3 - Componentes - S.png [ 1.16 MiB | Viewed 1938 times ]

Attachment:
Sonic 3 - Solda - S.png
Sonic 3 - Solda - S.png [ 1.3 MiB | Viewed 1938 times ]

Better resolution here and here.
Oh, and I noticed I forgot to take a picture of the assembled board. :-(
But I found a similar one here
If someone could please RE this board for me, I would be very happy. :-)

Thanks in advance!


Last edited by Fisher on Tue Mar 06, 2018 5:59 am, edited 1 time in total.

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PostPosted: Sat Feb 24, 2018 9:49 am 
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I traced it out about a year ago. It's not that complex. Most of the functionality of the logic revolves around changing between sonic 3 mode as an individual cart, and sonic & knuckles + sonic 3. That gets controlled by B27 #RESET. the S&K grounds that pin permanently for the S3 cart. Could be some errors with my schematic. I only beeped out the interesting parts with a DMM.


Attachments:
File comment: Sonic 3 schematic beeped out.
2018-02-24 10.43.53.jpg
2018-02-24 10.43.53.jpg [ 2.4 MiB | Viewed 1923 times ]

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PostPosted: Sat Feb 24, 2018 11:01 am 
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This reminds me of my own problems with my Sonic 3 cartridge I've had since 1994. It never saved games, but I didn't consider this a major issue as a kid. Only recently I got curious about it again and decided to check what could be the problem, and to my surprise, the FRAM appeared to have been intentionally disabled, as one of the traces leading to it was cut.

I have no idea why anyone would do that, specially considering this was an original TecToy cartridge, bought sealed from a respectable store.

I haven't tried to restore that trace yet, but I guess it would be cool if my cartridge was finally able to save.


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PostPosted: Sat Feb 24, 2018 11:06 am 
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infiniteneslives wrote:
I traced it out about a year ago.

Thanks!
That's cool!!

An interesting thing I noticed is that my game (besides the 74HC139 and the 74HC74) uses 2x 74HC00, while yours use an 74HC157 and a 74HC00.

I finished my 1st RE try a whyle ago.
I also lokked at the FeRAM circuit only.
Probably has lots of mistakes/omissions:
Attachment:
File comment: Try 1
Sonic3 RE - Try1.png
Sonic3 RE - Try1.png [ 1.16 MiB | Viewed 1907 times ]

I don't think a SRAM mod would be much difficult, but I have no idea where I could put a socket for a battery and be able to close the cartridge normally. :roll:

I also found something about the MegaKey here.
Altough it's a MegaKey 2, I don't understand properly the schematics and didn't found the IC's datasheet around. :oops:
Looks like there's lots of NANDs and 2 latches on the final draw.

Maybe I have a problem with the MaskROM.
That could explain why the thing only boots with the adapter.
And I tought they were almost undestructible!! :-b

tokumaru wrote:
I have no idea why anyone would do that

That's odd!!
I think this one is a TecToy too.
The difference is that I got this as garbage.
I also have high hopes to get it working properly!!


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PostPosted: Sat Feb 24, 2018 1:20 pm 
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Fisher wrote:
I also found something about the MegaKey here.
Altough it's a MegaKey 2, I don't understand properly the schematics and didn't found the IC's datasheet around. :oops:
Looks like there's lots of NANDs and 2 latches on the final draw.
That schematic looks like a lot of "generate a bus conflict and win!1!one"

that page wrote:
It consists of two input elements DD1.1 ("AND-NOT", address 508000H) and DD1.2 ("And", address 600002H).
Hm, adjust the addresses, and that's getting in a fight with $A10000, the VERSION NO register, where D7 is Intl/!Jpn and D6 is PAL/!NTSC
and $C00004, the VDP STATUS register, where D0 is VDP PAL/!NTSC



The schematic of your Sonic 3 cart looks like a fairly standard 4MiB game + battery-backed RAM SMD cart schematic to me...


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PostPosted: Sat Feb 24, 2018 3:21 pm 
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That's pretty interesting!
But I don't understand why the game boots with the adapter and not without it.
Any ideas?

Maybe the resistor bars have something to do with this...
I'll take a look at what they're doing.
I think a picture should be helpful too...


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PostPosted: Sat Feb 24, 2018 4:15 pm 
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Hm, I was actually only describing what was in Рис.1 and Рис.3

I hadn't actually looked at Рис.2 ... but looking closely now it appears to be describing the reverse-engineering process.

Рис.4 and Рис.5 are an all-new-parts implementation of the same schematic, using Soviet part numbers.

Quickly looking things up:
КР1533ЛЕ4 ↔ 74'10
КР1533ЛА1 ↔ 74'20
к555ап5 ↔ 74'244
КР1533ЛА2 ↔ 74'30


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PostPosted: Sat Feb 24, 2018 8:12 pm 
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Image

More info about cartridge pins signals description:
http://www.hardwarebook.info/Mega_Drive_Cartridge


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PostPosted: Sat Feb 24, 2018 8:37 pm 
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The best description of the SMD card edge signals I've found is from manually combining the content in this post-
http://atariage.com/forums/blog/586/ent ... this-time/
with the additional testing in this post-
https://segaxtreme.net/threads/genesis- ... sis.14448/


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PostPosted: Mon Feb 26, 2018 5:37 am 
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Thanks guys!
Pretty valuable information!
I only need a little more time to "digest" it.

I think the description "game don't boots" is a little vague, so I did some tests to try to find what is happening.

With the cartrige's board only, tested with:
- No TMSS MegaDrive = black screen.
- TMSS MegaDrive = "Produced by..." screen, than black screen.
- Gamegenie = same results with the exception I got the Gamegenie's screens before.
- Sonic & Knuckles = boots with a corrupted screen and keeps resetting, just like this crappy video shows.

With the Megakey, all the above tests worked fine.
I notice that strangelly, when I pressed reset at the first time, I got a screen like this one:
Attachment:
File comment: Weird!
20180225_213341.jpg
20180225_213341.jpg [ 876.39 KiB | Viewed 1713 times ]

The game only resets after the 3rd reset press.

The MegaKey I have is a bit different.
It only has an epoxy blob, 4 switchs and 3 parts marked as RP1 to RP3.
All the 4 switches have one pin plugged to GND, the other pin goes for the blob.
More or les like this:
Code:
A  B  C  D
|  |  |  |
o  o  o  o
 /  /  /  /
 |__|__|__|__GND

I called A, B, C and D the indivitual pins of the epoxy blob the switchs connects to.

By the markings and format of the other parts, I suppose they're resistor bars. (is this name correct?)
They're connected like this:
Code:
RP1 = 7A102J (near the upper cart connector)
+ | A17 | A16 | A15 | A14 | A13 | A12 <-Connector pins
   
RP2 = SLIP A5 102J (near the console connector)
+ | A24 | B25 | B24 | B23 | B22 <-Connector pins
   
RP3 = A102G (near the console connector)
GND | A20 | A22 | A19 | B22 <-Connector pins
     

Would these resistor bars be responsible for the game working with the adapter?

Maybe it's a problem with the MaskROM, but to confirm this I would need to dump it.
I have found some options, including one that uses a SegaCD to dump the game.
But unfortunatelly I don't own a SegaCD, and I need to take a better look before trying to build any of the other options.
If someone can please do a similar program that can do that without a SegaCD, I'll be very thankfull. :wink:
This one particullary seems to be a good option to me.

Thanks in advance.


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PostPosted: Mon Feb 26, 2018 7:12 am 
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Use diode test and measure each IO against VCC and GND, they should all show very similar results. If one differs from the rest then that pin may be fucked. I revived a SoR2 cart by placing a pullup resistor on a pin that didn't match the others.

Sonic 3 will boot without any of its companion hardware present provided you wire !CE and !OE pins to the ROM properly. If this most bare config doesn't work then it narrows the problem down to PCB and ROM. If all traces reach the ROM from cart edge you have a bad ROM at your hand. The PCB uses crappy glue vias that may fail in some way.

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PostPosted: Mon Feb 26, 2018 7:29 am 
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I had already wired the !CE pin straight from the cart edge to the ROM and got the same results.
I'll do the diode test on all ROM pins as soon as I get home.

What is very weird is that it works fine with the MegaKey, would it be it's pullups/pulldowns that are doing the "miracle"?
I'm seriously thinking in replicating it on the PCB.


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PostPosted: Mon Feb 26, 2018 11:56 am 
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Yes! That was it!
Thank you so much TmEE!
I tried the diode test with the - probe on vcc and got about 20 different readings.
But with the inverse (+ probe on gnd), I got only one different reading.
I soldered a 1K pull down and bang! It worked alone!
Thanks again!

I forgot to ask about the save RAM, does the game really use 1kb to save?
If so, I can plug it's A8 pin to vcv and it should work.
But maybe I should install a 16Kb SRAM with a simple battery circuit.
The SRAM would make a future fix / maintenance easier...
But there's the space problem...
What do you guys think?


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PostPosted: Mon Feb 26, 2018 12:09 pm 
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Very nice, another cart saved ~

I wouldn't bother at all with SRAM, the FeRAM is better though it has limited writes durability but you do get unused part of the chip only top address line change away.
EDIT: fixed stuff. I looked at my old research and there's 320 bytes of save data actually used in Sonic3 alone, rest in S3&K.
Image

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Last edited by TmEE on Mon Feb 26, 2018 12:24 pm, edited 2 times in total.

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PostPosted: Mon Feb 26, 2018 12:16 pm 
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This ram is 100% pinout compatible with 6116. As you can see from schematics, A9/A10 (which is NC in this chip) is tied to GND so this game uses 512 bytes of RAM.


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