Aliens - Bad chip, who could flash new chip?

backstagehobbies

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I've got an Aliens board with a bad character rom chip, J or K 8 on the board can't remember which but easy enough to verify. Cleaned, reseated, etc. to no avail. Swapping the chip wouldn't be a problem but I have no programmer nor the chips themselves to make a new chip to replace with. Is anyone handy and could flash me a new chip? Let me know if so and price, its all I need to make this guy work perfectly ^_^
 
Just fyi, the chip may be ok. I'd first check the enable line(s) and all address/data lines for activity. If the chip has no enable, its like it ain't even there. If a data/address buffer is bad, it interrupts the flow of data to/from the chip.
 
Maybe the quickest way to shoot down the problem would be to find a known good board and swap that chip into yours. If the problem remains, its not the eprom's fault.
 
I'm going to say I'm nearly certain of this; not positive but nearly.
Board was bought online as "working", got it plugged into a cab with a known, good, harness, power supply, etc. in fantastic shape (held my X-Men 2/4 player board until I got a 6 player). Plugged it in and get great initial screens, etc As you start or the demo starts however characters on screen are fouled up. Kick it over to test mode and it cannot read the chip. Working on the board and cables and everything I knew how to test (and a few that were learned from others) everything else seems to be checking out fine physically, just cannot read the chip. The guys I bought it from walked me through several items as well; it was working when they listed the board on eBay and apparently just before it shipped but not after.
So, I'm guessing chip.
 
I'd check the output enable line with a probe to ensure that the chip is being activated. If it's hard enabled then it's most likely the chip but if it's IC controlled it could just be a bad connection/trace or just a bad IC.

If you don't have a probe, I would suggest picking one up for this hobby even if you don't plan on repairing a lot of boards. Having a multimeter with continuity test and a logic probe are two things all arcade hobbyists should at least have.
 
Is this a Konami "Aliens" board? You confused me a little with your talk of the 6-Player X-Men PCB.

Although, it doesn't matter which one you have if it is a Konami PCB. The Konami boards from that era don't have socketed character or background ROMs, they are mask ROMs that are soldered directly into the PCB. The only removable chips are the program ROMs.

Are you sure you are correct on which ROM is bad?

Brian.
 
Sorry about the confusion ^_^ The board in question is indeed a Konami Aliens; I mentioned the X-Men because it is -now- in a cabinet that formerly housed a 2/4 player X-Men board. I decided to get Aliens and put it in that cab after I got a 6-player X-Men cabinet. Don't need a 2-player version when I have the full 6-player ^_^

Yea I am, mostly, correct on what chip is throwing the errors but could be mistaken about what exactly that error is. Game play is fine, title screen is fine, the photos in that opening sequence is fine, background on the stages are fine. Sprites are screwed up, but not all of them; the Ripley character is OK, as are a few items, but the Player 2, most all of the Alien sprites, and a lot of the other elements are screwed up/non existent. The test mode diagnostics come clean on everything except the one chip.
This chip I have done everything I could think of and a few things others could think of to get it to work; the sales folks I bought it from had it running up till the day they shipped it to me.
 
Ok, got it. :)

I don't own an Aliens PCB, but from all the pictures I see online that ROM doesn't appear to be socketed. If that board is the same as the other Konami's I've fixed from that era (Simpsons, Metamorphic Force, Sunset Riders) the mask ROMs that are at J8 & K8 are pin compatable with a 27C800 4 Meg 42 pin EPROM.

I can burn the code onto one of those for whichever chip you need, but there are a few things I would recomend you check before that.

There is possibly a bank of 8 74LS374's that connect to those ROMs. If one of the two that connect to J8 & K8 have failed it will cause the ROM to not pass the test. Use a logic probe to see if any of the pins are dead. There could also be a few other TTL logic chips connected to the address lines, verify they are good as well.

The reason I am suggesting this is that the traces that connect that mask ROM to the rest of the PCB are very thin and could break easily if you have to remove an unsocketed ROM. Taking the ROM out should be the last resort after you have checked every other possible reason for the failure. That being said, it is true that those mask ROMs are prone to failure, it's just not the reason for bad graphics or a test failure 100% of the time.

Brian.
 
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