What's new
By:

Zero Gunner 2 NAOMI Cart - Grave of dead boards with bad IC

TheDeath

TheDeath

Professional
Joined
Jul 2, 2017
Messages
431
Reaction score
400
Location
Italy
Do any of you tried to repair naomi carts?
I don't know why but looks like ZERO GUNNER 2 has a 80% failing rate. I know a lot of friends, mine including, that have this game with the infamous/random BAD IC (it could be all BAD or most cases IC7/8).
I've never read about someone that was actually able to fix this problem.
Some of them talk about a bad tsop rom, others clue about some buffers on the pcb (LVCH16245A and LCX16373).
My board was in the worst case, giving me all of the roms in BAD while doing tests. That, to my opinion, was really unlike to be the real problem, so i started to doing some work on it.

First i compared the 27c322 bios with the dump, winmerge told me was the same.
Then i went for Aliexpress and bought all new buffers for it, tssop48. I soldered them with my hakko and check with a digital scope for good connections and bridges. I've read many complaint about these, since i was not able to test them with my probe i decided to change all of them in a row.
Guess what? Nothing changed.

Then i went for change all of the smd caps just to be sure those were fine and again nothing happened.
I'm actually stuck here.

Do any of you had some experience with these?
 
Zero Gunner 2 only uses 5 MASK ROMs so error in IC 7 is a bit strange.

Can you show a picture of your PCB ?

Also a picture of your ROM TEST screen please.
 
rtw said:
Zero Gunner 2 only uses 5 MASK ROMs so error in IC 7 is a bit strange.

Can you show a picture of your PCB ?

Also a picture of your ROM TEST screen please.
Click to expand...
Well.. thats not correct. ZG2 does have 5 tsop roms but the bios handle them as they are 10. Basically each of them is splitted in 2 by the test, so IC7/IC8 is actually the fouth tsop on the pcb (IC9/IC10 is the fifth, and so on).
Test gave me all ic's BAD, the pcb is the same as the others. 5V and 3.3V are also set correctly.


PascalP said:
not sure if you have seen this topic, perhaps it can help?
NAOMI Cart wont load
Click to expand...
Thanks pascal. I've tried to lift pin 28 on the srams but unfortunatly no luck. All of the dead ones i've heard just go to a black screen after the naomi logo and sits there forever...
 
You're correct, the classic SEGA trick of two "virtual" chips in one physical.

When you say BAD, did you get a checksum of were they all the same.
I would appreciate a picture of the ROM TEST screen :)
 
I'd imagine in this case mask(?) roms might really went bad. it is not common for Sega-made games, but 3rd-party publishers may be used other vendor ROM ICs, lower quality.


TheDeath said:
I've tried to lift pin 28 on the srams but unfortunatly no luck. All of the dead ones i've heard just go to a black screen after the naomi logo and sits there forever...
Click to expand...
that topic is about protection parts issues. if ROM TEST shows all GOOD but game hangs after NAOMI logo - it is definitely the case.
I think it may be fixed in quite easy way - grab "netboot" ZG2 image, cut 1st 4MByte chunk from there, burn it to some EPROM and replace IC22.
 
MetalliC said:
I'd imagine in this case mask(?) roms might really went bad. it is not common for Sega-made games, but 3rd-party publishers may be used other vendor ROM ICs, lower quality.


TheDeath said:
I've tried to lift pin 28 on the srams but unfortunatly no luck. All of the dead ones i've heard just go to a black screen after the naomi logo and sits there forever...
Click to expand...
that topic is about protection parts issues. if ROM TEST shows all GOOD but game hangs after NAOMI logo - it is definitely the case.I think it may be fixed in quite easy way - grab "netboot" ZG2 image, cut 1st 4MByte chunk from there, burn it to some EPROM and replace IC22.
Click to expand...
Interesting. But i wonder what this "netboot cut" might do if the tsop are bad? Since the game sprite/tiles are there... if they are really bad, whats the purpose on that?
 
TheDeath said:
Interesting. But i wonder what this "netboot cut" might do if the tsop are bad? Since the game sprite/tiles are there... if they are really bad, whats the purpose on that?
Click to expand...
its not your case. it is ONLY for the case if ROM TEST passed as all GOOD but game wont work, which means protection chip issues.
using mentioned procedure game program may be replaced with cracked one, which doesn't use/require protection-decryption chip (Sega 317-something)
 
Here's the test screen result...
 

Attachments

  • thumbnail.jpg
    thumbnail.jpg
    116 KB · Views: 81
Oh wow.. i just got the loading screen!
I tryed anyway the solution posted by metallic and burned the first 4mb chunk to the 27c322 at ic22, i was greeted by the "now loading game" after the naomi logo.
The game now sits there. i tryed to lift (again) pin28 of the srams but nothing changed.
At this point i must really suppose that, all suddently, all of those tsop are gone somehow (i had this for a while and i remember had IC7/IC8 bad, only that one), i probably ended up stressing it too much by doing all of the work on it.
 
Thank you for the test screen images, it looks like the system is pulling in some kind of data.

Do the checksums change between powercycles ?
 
rtw said:
Thank you for the test screen images, it looks like the system is pulling in some kind of data.

Do the checksums change between powercycles ?
Click to expand...
No it doesn't... result is always the same one with same numbers and letters
 
Then iIt looks like your you are missing address lines or data lines.

Maybe desolder one of the ROMs, dump it to verify that it is good before you go any further ?
 
You must log in or register to reply here.
Back
Top