Eprom Help

KidVidiot

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I am trying to get the sound/speech working on an Astro Blaster (Sega G80). I currently get neither, just a faint hum from the speaker. I did the self test and the Eprom test listed Eprom 889 and 891 as BAD. I've been studying the manual back and forth but can't find the significance of the part numbers or how they help me. They aren't in the schematics or in the lists of parts. How do I find these two bad eproms? And what should I do once they're found?
 
Those are Sega EPROM numbers. Sega has been using sequential numbering for all of their EPROM code since just after the dawn of time. There should be labels/stickers on your EPROMs, with numbers on them. They're often "EPR###".

According to MAWS, those numbers are from the "version 2" of Astro Blaster, and are associated with locations U2 & U4. When you find them, they'll likely be 2716-type EPROMs. You'll want to pull them, put them on your EPROM programmer, and read/verify them. If you confirm they're bad, you can try erasing them in a UV eraser, or program the proper code onto another couple of 2716 and put them in.
 
Bad EPROMs are rare, a pair of bad EPROMs on the same board is more likely a problem with the chip select or output enable logic, but you should always verify the ROMs as its easy to rule it out.
 
Yes, silly me, I should have actually looked at the boards again before posting. I kept scouring the manual and schematics for those numbers when in fact like you said they were printed on stickers right on the eproms.

So the plot thickens a little - the two eproms that came up as bad on the self test are the only two eproms on any of the boards that aren't original. They are a different chip manufacturer and were obviously put on later on. They are also labeled "Fire" and "Fuel" and are on the eprom board. As far as I know, my fire and fuel work fine, so I'm not sure if they actually aren't working, or if the self test is calling them bad because they are different, or what.

In other news, I actually fixed the sound problem (for the most part). I really should have checked the speaker wires first before trying to mess with the boards (now I know). One of the wires had come off, and when I connected it back "FIGHTER PILOTS NEEDED IN SECTOR WARS" came blaring out. Now the only issue is that something might be wrong with the pot - when it's turned all the way down the sound is at a normal level, and turning it up at all makes it blast out like it's going to blow the speakers. Also when it's all the way down the speech seems like it's at a normal volume but all of the bass-heavy sound effects are noticeably louder, really rattling the speakers (again this is with the pot turned all the way down).
 
So I found the two original eproms stashed away in the bottom of the cabinet (i'd taken them earlier but had forgotten where they came from). Perhaps a previous owner had switched roms to make the game easier, and the new hacked roms just show up in the test as bad because they aren't recognized in the test? I'm going to switch them back out for the originals and see...
 
The fact they are flagged as bad is because they game code does not find the data it expects to in those chips, because it is the hack. The original roms should clear the error but not because the replacement ones were bad, they just had different contents.

Your lack of speech or sound is probably not related to the error in this case. Are you sure the amp is even working?
 
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Yes I fixed the sound and speech per post #4. The speech really adds so much to this game, it's pretty great.

Now to just get the speech on my berzerk working!
 
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