Question about ROM Chips

ArcadEd

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So I have a Off Road board that I have narrowed the problem down to one chip, U15. I burn a new one, put it in and the game has the same issue. Take the chip out, read it and retest it in RomIdent and it's failed. I have done this 3 times now.

What could be wrong with the board causing it to corrupt a rom chip each time it's fire up?

Plus, I can just rewrite the chip without the need to erase it. I don't understand

Thanks
 
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... or you left it under the uv light too long while erasing it and it will no longer program. Make sure to run a verify from your programmer software after burning it to make sure it programmed ok
 
Yeah, writing and verify comes out fine. I even read the chip back to bin and verify it manually in RomInit before putting it back into the board.

I am 99 percent sure I haven't been putting it in backwards this whole time because I am usually pretty anal about that. Who knows though.
 
Although I doubt it would affect one chip, you could have a shorted trace somewhere sending 12v where it doesn't belong - frying the chip, or if there's jumpers involved they could be set wrong for the type of chip you're using.

Is it a number-for-number replacement?
 
Yeah, number for number swap. Seems to be killing more than one rom.

I measured my 12v on the board and it's near 15v? Is that normal?
 
OK,
I have a feeling something else got damaged in the process. Before I could get a picture, and play (it would just freeze every 4 seconds). Now I can't get a picture.

Ed
 
... or you left it under the uv light too long while erasing it and it will no longer program. Make sure to run a verify from your programmer software after burning it to make sure it programmed ok

Any guidelines on what is considered "Too Long"? I think I have my eraser set to around 10 mins.
 
Well I have 2 Super off road boards and both do the same thing in terms of voltage.

My PS is running at 12.5-13v with nothing plugged in. Off Road requires a 5.20 voltage when tested on the board, to get the my PS runs at about 13.9v with nothing plugged in.

Now when I apply power to the PCB, my meter reads 15v on 12v connections on the board and when I measure at the PS it measure the same, about 15v
 
Is that a switcher or a game-specific supply? Sounds like a sense circuit isn't working good. Sometimes on switchers too - the more you turn up the 5v, the more the 12v goes up with it (although not to 15v)

Chances are more of your roms got toasted...since you have a burner you can verify them all.

10 min should be fine in an eraser...I think some people thinks its takes HOURS and thats what can perm kill a rom.
 
No, just one switching power supply to the board. There is a top board and bottom board and a power connector that connects the two. I am measuring the 12v there, that is where it reads 14.5v.

I am attaching a picture, might make more sense.

The connector to the right is the power coming in.

Then you can see the one connecting the two boards, that is where I am measuring the 14.5v

Ed
 

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Just for giggles, get two adjustable switchers, bridge the neutrals, connect 5V to one, and 12V to the other. Adjust them for 5.2V and 12.0V respectively. If it no longer corrupts your ROMs, well, there you go.

I've seen (recent, redemption) machines come from the factory with completely separate power supplies for every voltage. If it gets the game going, I don't see any reason why not. Just make sure you bridge the supplies' neutral (aka "return", "logic ground", "supply ground" etc. almost always black wire) leads.
 
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I did something else first and just disconnected the 12v all together and game fired up. Could the 12v be for sound only? Hence blowing the roms that related to sound?
 
The chip in question is an EPROM, correct? There should be no 12V going to any EPROM, so I don't see how that could be the issue. What exactly is the chip? Maybe you're trying to use a standard JEDEC EPROM where a masked-ROM pinout is expected?
 
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