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Brentradio

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I have this Sega 16B Shinobi board that was converted to Altered Beast. There is a graphics glitch on anything that moves with vertical lines through the characters.

Should there be a chip in the socket with the red arrow? If so which chip?

AlteredBeastMine1.jpg


DSCN3327.JPG


DSCN3336.JPG


DSCN3338.JPG
 
I've found pics online that show an Golden Axe pcb with this chip, and a Shinobi pcb without this chip. (see pics below)

So I'm thinking maybe I do need it.

Anyone know which chip this is?

Thanks!

:D

These are NOT my boards.

5797-GoldenAxe.jpg


Shinobi_-_1987_-_Sega.jpg
 
The IC which is missing on your board is the i8751 MCU, this is used for protection on some revisions of the games.Anyway you don't need it since your board boots without it (you have a ROM set that doesn't require it, a missing MCU would result in no boot).The vertical lines though sprites are most likely caused by a fault on the ROM board.Try for first to dump the object ROMs and compare dumps agains MAME.
 
Thank you.

Well, if the fault is with the rom board the I would guess that the new rom board for the multi should fix the issue.

I guess I'll just wait for the multi to come out.

:D
 
Easy way to find out which e(prom) this is, move your finger around the eprom legs as the board is powered up, and keep watching the screen. Chances are the lines will flicker if you find the culprit.
 
Easy way to find out which e(prom) this is, move your finger around the eprom legs as the board is powered up, and keep watching the screen. Chances are the lines will flicker if you find the culprit.
Hmm, well I tried that but didn't see anything. Not sure as some of those are really close.

Thanks for the tip.
 
I'd be surprised if you had a ROM issue here. Those lines are spaced far enough that I doubt it can be something so simple as a stuck or floating data line, and it doesn't have the cadence of addressing errors. The lines look like one bit has floated high. it's possible, but it makes me worry about the 16B board below. I don't remember if the sprite buffer RAMs are external to the sprite hardware, but if so, that might be a good replacement candidate.
 
Thanks for the pics and info guys!

I'm not technical enough to go any further. I'll just wait for the multi and see what happens and go from there I guess.
 
TLDR:

Yes, it's missing a security missing a chip.

But that's not what's causing your graphics problem.

The security chip is not needed on resurrected boards.

Test the rom board out with a known good bottom board to isolate your graphics fault.
 
Thank you for the reply.

I only have this one board which I bought for the multi. I've just decided to wait for the replacement romboard in the kit and see if that solves it.

:D
 
So I just picked up another untested Shinobi board.

All it does is this: (It changes with the attract mode as you can see in the other two pics)

DSCN3516.JPG


DSCN3517.JPG


DSCN3518.JPG


If I swap the rom board out with the original one I have, it still does the same thing, same rolling picture.

When I swap the new Shinobi rom board out with my old Altered Beast rom board, I get the same fault but now with Shinobi. All of the moving characters have the lines through them like in the pics in the first post.

So this leads me to believe that the fault is the original main board and not with the original Altered Beast rom board.

I would also guess that my new main board is the fault for the rolling screen since it does the same thing with either rom board.

?(
 
Looks like a missing sync signal. Could be an easy fix.
And yes, problem is with the mainboard.
 
Do you have two s16 to jamma adapters? Are you testing with the same adapter?

The screen looks like what you get when you leave out the video ground on many s16/s18 boards.

As for the lines problem, that's not romboard-related it would seem that the mainboard with the stable picture has some issue. Maybe trace damaged or video ram?
 
I agree with above, re absent video ground.

Most sys16 pinouts don't specify video ground and I've encountered a few adapters that neglect to include it.

Easy to check, just run a wire from jamma pin 14 to one of the outer ground pins. Bet that fixes your issue immediately.
 
Do you have two s16 to jamma adapters? Are you testing with the same adapter?
I'm using the same adapter as I only have the one I bought from arcadeshop.com

If anyone is up for this deal, I will send you both boards and you send me back one working one and keep the other one.

Any takers?

:D
 
Yeah, looks like a bottom board problem to me too.

This will help you understand how your board is setup.
https://github.com/mamedev/mame/blob/master/src/mame/drivers/segas16b.cpp


For the AB board, find the (character) roms, and check the corresponding traces/chips on the bottom board.

For the shinobi board, find the sync pin, and trace back to the sync chip on the board. Pull the schematic on it, and try and tap sync directly from the chip. It's usually near the front of the board.

So I just picked up another untested Shinobi board.

...


If I swap the rom board out with the original one I have, it still does the same thing, same rolling picture.


When I swap the new Shinobi rom board out with my old Altered Beast rom board, I get the same fault but now with Shinobi. All of the moving characters have the lines through them like in the pics in the first post.

So this leads me to believe that the fault is the original main board and not with the original Altered Beast rom board.

I would also guess that my new main board is the fault for the rolling screen since it does the same thing with either rom board.
 
I'm using the same adapter as I only have the one I bought from arcadeshop.com
If anyone is up for this deal, I will send you both boards and you send me back one working one and keep the other one.

Any takers?

:D
PM sent ;)
Wouldn't hurt to have a second motherboard. :D
 
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