Question about ROM Chips

[ArcadEd]

OK, so it's the one chip each time, U15. I don't have the 12v hooked up at all right now and the chip is dead again.

What is happening is in game, as soon as a sound effect is suppose to happen the game pauses, for about 3-5 seconds, then continues for about another few seconds before pausing again, looking for sound.

Whatever is happening is what is taking out U15, I have duplicated the issue in MAME by creating a blank rom for u15 and the game plays the exact same way.

I just don't understand what could be causing it. Glad to know it's not the 12v though.

 

[ArcadEd]

This is driving me insane.

I can 100 percent duplicate all of my issues in MAME. If I put my bad u15 rom into mame and start the game not only do I have the same bug during gameplay, but when I go into diagnostics and test audio, I get the same error. Audio Processor Not Responding.

I can't understand what keeps corrupting that one ROM. I took all the boards apart, just to inspect for anything.

Should I start testing resistors or something?

 

[Womble]

Check the voltage between pin 22 and pin 14, the only way the chip could be inadvertantly programmed is if pin 22 has 12 volts on it. But as its the OE pin if there was 12V on it the upstream logic would be totally smoked.

Possibly you have a bad EPROM chip, I have met a few that wont hold their contents. Try writing to the chip and then just leaving it for a week, then reread and compare. Alternatively you could use another PCB, any game would do as long as the gfx ROMs are 27512s, put the suspect chip on that board, the game gfx would be a mess but after running it you could take it out and reread it to see if it has lost its contents, that would tell you if its the board that is somehow causing the problem, or if its the chip itself.

 

[ArcadEd]

Thanks,
I have a stock of 25 of 27512s, I hope not all of them are bad, I have tried about 6 different ones so far, including one that came off the board.

I metered every pin to ground and never got over 5.21v on any pin.
I get 5.2v between 14 and 22

 

[ArcadEd]

I did what you suggested. I took out one of the roms with sprites, and put it in the spot that u15 is.

It corrupted this chip too. I took it out after a few minute, read the bin and compared it and it says it's blank.

HOWEVER, when it put it back into the board it seems to be working fine. (Could just be I didn't get to a bad part of it yet)

I am reading and programming all of my chips at the +2 speed in the GQ software, is that ok?

 

[mattosborn]

Sounds like your EPROM programmer is the only thing corrupted....

 

[ArcadEd]

I started to think the same thing, but I don't think it's the problem. (The issue earlier was solved with a reboot).

I can write a chip and then 2 hours later read it back to bin and RomINIT recognizes the rom correctly.

But when I put it on the pcb, start up the game and then remove it, read it, RomINIT says it's unknown, blank or bad rom.

 

[Womble]

I am begining to suspect your eprom reader is the cause of the false reads. Try setting it to a different chip, ie if yours are Intel D27c512s, try telling the programmer there are AMD 27512s instead, or choose the generic 27512 option instead.

Does your programmer complain if it sees "out of spec" pins? If not you may just have dirty leg contacts, a blank read could be caused by poor connection on the C/E line. A corrupt read could be cause by poor contacts on any Address or Data line.

 

[ArcadEd]

My reader isn't really complaining at all. Here is a real quick step by step of what I am doing so please let me know if something seems out of wack.

Game freezing/pausing when sound is suppose to be played. I can simulate the error in MAME by killing rom u15.

1. Pull rom u15 from PCB. Read on programmer. Save to file. Open file in RomInit. Rom reads bad, blank or not found.

2. Program new Rom using mame rom for u15. After writing rom, read it to file and check with RomInit. Checks fine. I reread the rom about 8 times within 2 hours to make sure it was still good with each read in RomInit. it is.

3. Put new Rom on pcb. Fire up game. Sound issue still exists.

4. Remove Rom, read to file with programmer. RomInit shows not found, bad or blank Rom.

Hopefully I condensed that enough.

I guess my point is, if the programmer was messed up, why would it read the rom as good until I put in the PCB?

 

[ArcadEd]

Well if it is my programmer, would anyone be willing to burn me U15 from the MAME offroad set on a 27512? I'd be happy to paypal some money over. Since I am pretty sure that i the bad rom.

If not, I can ask bob if he can with my next order.

Ed

 

[baritonomarc]

Try burning a ROM for another (but 100% working) PCB and see what happens: if the burner works the PCB with fresh burned ROM will still work, if not the PCB will show some problem