ziggaboogi
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Joined: August 2020
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Post by ziggaboogi on Aug 9, 2020 16:02:25 GMT
Hello, hoping that someone might be able to point me in the right direction.
I recently added a socket to my VA0.8 US Saturn. I know that the install was correct as I can still insert the original BIOS chip and have no issues running.
The problem comes up when I installed a burned RF BIOS. The first one I burned did in fact boot up correctly and allowed me to play Daytona USA (US) and Nights (JP). However when I was putting the system back together it stopped booting correctly. I've already verified the chip again and it doesn't seem to have any issues.
I also verified that I don't have any broken traces on the 40 pin socket by going along all the test points in the schematic and also verified that the original BIOS chip still boots up with no issues.
I'm burning the BIOS onto AM27cC400 chips and assumed that would be okay seeing as I was able to get the RF BIOS to boot at least once..... Any ideas why it wouldn't boot up anymore after a single successful boot?
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ziggaboogi
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Joined: August 2020
Posts: 3
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Post by ziggaboogi on Aug 9, 2020 17:35:32 GMT
Ok so weird new development with the BIOS. I've somehow figured out that the rf shield is the thing making it not boot correctly.
Somehow, and I'm not sure how, if the RF shield is in close proximity to the Eprom the system wont boot. I thought at first it could be a short somewhere but with the original BIOS and the rf shield installed properly the system has no issues. Also I've experimented and found that if the RF shield is just near enough to the EPROM, not even touching it or any part of the system. It prevents the bootup.
Right now the only thing on the EPROM is a paper sticker. Has anyone even heard of anything like this before?
EDIT: So now I've done more testing and found that if anything is covering the window of the EPROM more than a piece of paper, it doesn't boot??? So if I put a piece of electrical tape, hold a piece of foil over it or a piece of cardboard about an inch away, it prevents the system from booting.
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Post by zyrobs on Aug 9, 2020 21:18:18 GMT
I'd try erasing and re-burning the ROM.
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ziggaboogi
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Joined: August 2020
Posts: 3
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Post by ziggaboogi on Aug 9, 2020 21:27:38 GMT
Already tried erasing and burning again. Still having the same symptoms. Somehow I have a sega saturn that's only region free when it's in pieces lol.
The weird thing is that when I verify the chip both with and without having the window covered, the programmer doesn't see any errors when compared to the bin file.
At this point my only option is to order some more replacements chips as the only other chip I have seems to be defective as it can't complete the write. I'll update once I get the new chips in a few days and try again.
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traian
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Joined: August 2020
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Post by traian on Aug 20, 2020 23:02:14 GMT
You should try 27c160. I never had problems with them. Plus you can make a 4in1 bios.
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