IC identification when the part number has been removed

gamefixer

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IC identification when the part number has been removed

Working on a board that has a bad IC that has had its part number scraped off. Its a 60 pin surface mount device that has something to do with memory control from my best guess. Board complains about a BAD ram with this IC installed so I swapped in a known good one and the board works fine.

Its a Irem board with no schematics, Pound for Pound.

Any pointers as to how to figure out what this thing might be?
 
Working on a board that has a bad IC that has had its part number scraped off. Its a 60 pin surface mount device that has something to do with memory control from my best guess. Board complains about a BAD ram with this IC installed so I swapped in a known good one and the board works fine.

Its a Irem board with no schematics, Pound for Pound.

Any pointers as to how to figure out what this thing might be?

I assume no one has schematics for this board?

Start with posting pics of the board and close-up of the area around the chip. Someone here may already know, or have clues.

Next, map out (as best you can) what the various pins are. The various voltage and ground pins should be easy to figure out. Next trace what each pin goes to (which pin, of which device). By looking up the connected device, you should be able to figure out whether each pin of the mystery device is an input or output, and the things that it inputs and outputs to should give a clue as to it's function. After that you'll have to try to figure out what chips with that function are called, and start digging through data sheets.

Good luck!
 
good pointers. Thank you.

I'm sure its some generic part.
 
Got a closeup pic of the chip and area around it?

Depending how good of a job they did removing the markings, sometimes you can still read at least a partial part number or even see a manufacturer logo if you look at it with a lighted magnifier at various angles. Licking your finger and wiping the top of the chip sometimes helps provide some contrast.

For arcade stuff, MAME source is also a good resource. Between the comments and of course seeing the code for the hardware that they're emulating, you can learn a lot about the hardware. In this case, it sounds like the chip you're asking about may be an 8751 based MCU: https://github.com/mamedev/mame/blob/master/src/mame/drivers/m72.cpp#L628 . Presumably, the part has an internal ROM, so simply replacing it with an unprogrammed chip wouldn't work. It looks like MAME just works around the problem, so you can't actually grab the dump and program a new part.

DogP
 
interesting find there DogP! It sure does look like this part.

http://www.datasheetarchive.com/dlmain/5b724f3a93c930a0aaaa58b880074dfd763d0d/M/D8751H

In the datasheet above it states that the part can be electrically programed and erased with UV light. Theres no window on the part on this board so I'd imagine that its a one time burn, is electrically erasable or does not have the on die ROM.

I'll check it out later when I get to the shop.

Thanks for the push guys.
 
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Usually IREM 8751 MCU in a 40 pin DIP package, you said the scratched-off one is a surface mounted 60 pin IC, for surface mounted we mean QFP and not PLCC of the different package of the 8751.Please, post a picture for a better understanding.
 
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OK, you mean the 'KNA91H014', this is used to generate the palette of sprites and tilemaps, you can find pinout of it in R-Type and Vigilante schematics.
 

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OK, you mean the 'KNA91H014', this is used to generate the palette of sprites and tilemaps, you can find pinout of it in R-Type and Vigilante schematics.

it looks like that part but I dont think its the same.

I'll take a pic tomorrow.
 
found an image online that should work.
 

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Why you don't think it's the same?If you are unsure, look at schematics of R-Type or Vigilante which carry this IC and compare connection of all pins (he 'KNA90H014" can have some pins tied to GND or not, this depends from game design, maye this mislead you).I'm 100% sure it's the same chip.This IC is used on Irem hardware of same era (M72, M81, M82, M85) and it's a common practice of Irem to scratch-off the part name on customs ICs, I have here a Major Title (M82) with them all sanded.Believe to a guy with hundreds and hundreads of boards repaired (and documented) and experience on most disparate arcade systems...
 
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IC identification when the part number has been removed

OK, you mean the 'KNA91H014', this is used to generate the palette of sprites and tilemaps, you can find pinout of it in R-Type and Vigilante schematics.



Little bit off topic but are those solder bridges intentional or is this something you're repairing due to that? It looks clean enough to be intentional but at the same time would be unusual.
 
Maybe you are not enough experience with electronics and in particular with arcade repair.As I said. some pins of this custom IC on some Irem boards are tied to GND (while in other boards are routed to signals).All these pins you see bridged are simply tied to ground since the pads are tied each other so when you put solder it creates a unique bridge.There is nothing repaired.
 
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IC identification when the part number has been removed

I'm just used to all pins having individual pads on a board, even for ground pins rather than them being bridged like this. I understand the reasoning behind it, but it just seems unusual to me to see it done that way.

I have seen ground pins soldered together on several Midway PALs though which again seemed odd to me given they're in a socket
 
It's a design choice.Again ,they are bridged not from me but on board where each GND pin is tied each other by a little trace.
 
Why you don't think it's the same?

Due to the IC's proximity to RAM and the fact that when removed from the board the game complains about having bad RAM.

It could very well be a KNA91H014 but, as you said earlier in this thread, "the 'KNA91H014', this is used to generate the palette of sprites and tilemaps" makes me doubt that it would be the same part.

I'd be happy to swap the part in and find out though.
 
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Little bit off topic but are those solder bridges intentional or is this something you're repairing due to that? It looks clean enough to be intentional but at the same time would be unusual.

Thats a pic I found online of another board. I'll get a pic of the IC on one of the boards I have and post it. There are a few factory bridges.
 
Sorry but you are talking without any knowledge.
How do you think palette is generated if not with values written in RAMs???
You didn't even check connections on your board and compared them to schematics of boards using the 'KNA90H014'.I attach snippet from R-Type and Vigilante ones, you can see how the IC is tied to address/data bus.
Perhaps you like to be a contrarian and doubt about what I said since you don't want to admit I'm right.Anyway it's not the fist time for me and I used to this behaviour of people :)
 

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Sorry but you are talking without any knowledge.
How do you think palette is generated if not with values written in RAMs???
You didn't even check connections on your board and compared them to schematics of boards using the 'KNA90H014'.I attach snippet from R-Type and Vigilante ones, you can see how the IC is tied to address/data bus.
Perhaps you like to be a contrarian and doubt about what I said since you don't want to admit I'm right.Anyway it's not the fist time for me and I used to this behaviour of people :)

damn dude, think much of yourself? Sounding a bit like another KLOV'r thats full of himself here. :) Perhaps its a language thing? I'm not putting any effort into doubting what you are posting. Thank you for the information BTW.

You're right, I didnt check connections, I will though. Seems like the connections to GND and +5 might be dead giveaways. Also the color outputs, I can probe those and if in fact they are color drives then its settled.

I dont have a donor for the part so I cant just swap it out but its worth investigating just to know whtat that part really is.
 
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