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Thread: sega cd corrput internal ram

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    Death Adder's minion PvtHinge's Avatar
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    Sega CD sega cd corrput internal ram

    Hello

    I got a sega cd the other day and I just can't format it.
    it says that the system has been formatted but it doesn't when I chick to see what data is on the system I get these random symbols and stuff.
    when I format it again it says that 236997 or something free space and the same amount is being used.
    I removed the battery and still no luck.
    Any advice?
    It is a old pal mega cd model 1. (Still has a eprom for a bios holder)

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    RORRING STAAAAART! Master of Shinobi FuturePrimitive's Avatar
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    Sega CD

    Post and search here for extra help:

    http://www.sega-16.com/forum/showthr...-repair-thread

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    Raging in the Streets xelement5x's Avatar
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    Maybe the battery is going out on it? If I couldn't figure it out I would probably try and remove the battery from the board, put in a coin cell holder, and then put the battery back in. If it still doesn't work then get a replacement rechargeable battery and give it a whirl.
    Quote Originally Posted by StarMist View Post
    A spine card is the hymen of a new game assuring its first owner that he is truly her one and only, and of a used game assuring its new owner that whilst she has been played with in the past that play has never been too careless or thorough.

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    Death Adder's minion PvtHinge's Avatar
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    Quote Originally Posted by xelement5x View Post
    Maybe the battery is going out on it? If I couldn't figure it out I would probably try and remove the battery from the board, put in a coin cell holder, and then put the battery back in. If it still doesn't work then get a replacement rechargeable battery and give it a whirl.
    I did that.
    I even left the CD to stand unplugged over night to make sure there was no power at all, but still corrupt issues.
    Sometimes it doesn't even let me do a format.

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    The medium-sized mang. Raging in the Streets Lastcallhall's Avatar
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    During one of the times you can format, can you save a game immediately afterwards, and then come back to that save spot?
    Last edited by Lastcallhall; 10-29-2013 at 10:28 AM.

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    Raging in the Streets xelement5x's Avatar
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    Quote Originally Posted by PvtHinge View Post
    I did that.
    I even left the CD to stand unplugged over night to make sure there was no power at all, but still corrupt issues.
    Sometimes it doesn't even let me do a format.
    Hmm, have you tried running the system without a battery in there at all? From what I understand all the battery does is trickle power the RAM that holds the saves. Without a battery you should still be able to turn on the system and format the RAM. If you can't then I would assume that the RAM is messed up.
    Quote Originally Posted by StarMist View Post
    A spine card is the hymen of a new game assuring its first owner that he is truly her one and only, and of a used game assuring its new owner that whilst she has been played with in the past that play has never been too careless or thorough.

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    Death Adder's minion PvtHinge's Avatar
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    Quote Originally Posted by xelement5x View Post
    Hmm, have you tried running the system without a battery in there at all? From what I understand all the battery does is trickle power the RAM that holds the saves. Without a battery you should still be able to turn on the system and format the RAM. If you can't then I would assume that the RAM is messed up.
    Yes I even tried that. I rsn the machine with out a battery. Still no luck. When ever I play again I get a screen tgat say internal ram not installed, there has been no way to get past there.

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    Sports Talker qzack's Avatar
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    I have a similar issue with my Sega CD model 1. Rather than start a new forum thread, I thought I would just chime in on here and see if anyone can help me.

    I have replaced the battery as I thought this was the issue to start with but I'm still not having any luck. The issue is when I run Sonic CD it tells me when the game boots to "Please Format the Ram" or something to that effect. When I go into the options menu and try to format the ram I get an error with a loud beep. It simply says "Cannot Format" and I can't continue in any way.

    In reading about this problem one thread said something about power and how the sega cd can lock the ram out if not enough power is getting to the system. When I bought this system on ebay the guy who sold it to me didn't give me the proper AC Adapters from sega. I have a model 1 genesis attached to this unit so I'm running two ac adapters. One AC Adapter is 9v but I know the mh is lower than the official sega adapter. The other adapter is from a Turbographix 16 which runs about 10v but I'm not sure on the mh rating. I have placed an order for official ac adapters in hoping it can fix this problem as I really don't want to replace the ram chips if it is as simple as a power problem.

    My question is would proper AC adapters fix this problem for good?
    Or are my ram chips gone and I need to get them replaced?
    Has anyone had this problem from using the wrong type AC Adapter..?

    I guess I'm looking for words of encouragement here as I've never had this issue even when I owned a sega cd back in the day of release. Obviously the guy who sold it to me didn't know about this issue or played games that didn't need to be saved to ram. Before he sent the system he forgot to get his Rebel Assault disc out of the cd tray, so in winning the auction I got a free copy of Star Wars Rebel Assault.

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    Death Adder's minion PvtHinge's Avatar
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    Quote Originally Posted by qzack View Post
    I have a similar issue with my Sega CD model 1. Rather than start a new forum thread, I thought I would just chime in on here and see if anyone can help me.

    I have replaced the battery as I thought this was the issue to start with but I'm still not having any luck. The issue is when I run Sonic CD it tells me when the game boots to "Please Format the Ram" or something to that effect. When I go into the options menu and try to format the ram I get an error with a loud beep. It simply says "Cannot Format" and I can't continue in any way.

    In reading about this problem one thread said something about power and how the sega cd can lock the ram out if not enough power is getting to the system. When I bought this system on ebay the guy who sold it to me didn't give me the proper AC Adapters from sega. I have a model 1 genesis attached to this unit so I'm running two ac adapters. One AC Adapter is 9v but I know the mh is lower than the official sega adapter. The other adapter is from a Turbographix 16 which runs about 10v but I'm not sure on the mh rating. I have placed an order for official ac adapters in hoping it can fix this problem as I really don't want to replace the ram chips if it is as simple as a power problem.

    My question is would proper AC adapters fix this problem for good?
    Or are my ram chips gone and I need to get them replaced?
    Has anyone had this problem from using the wrong type AC Adapter..?

    I guess I'm looking for words of encouragement here as I've never had this issue even when I owned a sega cd back in the day of release. Obviously the guy who sold it to me didn't know about this issue or played games that didn't need to be saved to ram. Before he sent the system he forgot to get his Rebel Assault disc out of the cd tray, so in winning the auction I got a free copy of Star Wars Rebel Assault.
    Mine did format (I was using a real 100% not 3rd part power supply too)
    I tried with a different power supply as well no luck.
    I read that you need to leave the sega cd to "charge" if it was off for a long time and i only then got the odd has 0 free space of 0 space glitchy-ness .
    I replaced the caps and the chip it's self and now it works... replacing the chip is not easy, it took a hell of a long time.
    here are some links where you can find a replacement or can just be of use to you.
    This chip I used but these are in South Africa like me... really made it hard to fix this. I swear I am the only person who has one here.

    http://za.rs-online.com/web/p/sram-m...chips/0391719/

    here is a website that has alot of useful info on the sega cd eg: part list

    http://console5.com/wiki/SRAM_64Kb:_8K_x_8-bit

    I recommend maybe buying a broken sega cd that can't ejected discs or some thing and just switch boards around.
    or getting a A offical Sega Mega drive or Sega Genesis power power cable (I know that the sega CD is picky about it's power supply) to power up the beast up.
    Maybe you will have more luck than me.
    Last edited by PvtHinge; 02-18-2014 at 07:03 AM.

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    Sports Talker qzack's Avatar
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    Thank you very much for the reply.
    The information you have provided has helped me.
    Now I just need to decide what direction I want to go.

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    Sports Talker qzack's Avatar
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    Attachment 8681

    Attached in a picture of a motherboard from a sega cd model 1. I currently have the problem where I can't format the ram and when I try to do so the unit just beeps and says "cannot format".
    I understand from posting here earlier that the ram on the motherboard can be replaced but which chip is it..? Can someone take this image and make a reference mark on it for me identifying which chip is the sega cd internal ram..?

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    Electronics Engineer Road Rasher db Electronics's Avatar
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    Quote Originally Posted by qzack View Post
    Attachment 8681

    Attached in a picture of a motherboard from a sega cd model 1. I currently have the problem where I can't format the ram and when I try to do so the unit just beeps and says "cannot format".
    I understand from posting here earlier that the ram on the motherboard can be replaced but which chip is it..? Can someone take this image and make a reference mark on it for me identifying which chip is the sega cd internal ram..?
    I get an "invalid link" message when I try to click on your attachment.
    www.db-elec.com
    Code:
    do {
        Genesis();
    } while (Nintendont());

  13. #13
    Sports Talker qzack's Avatar
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    I quickly tested the attachment when I first posted the message and it worked fine, so it must be a forum error or something.

    Here is another image which should do the job.

    http://img20.imageshack.us/img20/4789/dsc0439td.jpg

    I need to know which IC's are the ram chips or the chips directly responsible for allowing the unit to save games or put saves on it.

    In reading this article from console 5, they talk about this layout....

    837-8952 IC BD MEGA-CD MAIN BD EXPORT (171-6326B)
    IC1: CPU: MC68HC000FN12
    IC2: 315-5548
    IC3: PCM Sound: 315-5476A
    IC4: ROM: MPR-15045B-T
    IC5: DRAM: 424270-80
    IC6: Battery Backup IC: MB3790
    IC7, IC8: VRAM: TC611664Z-80
    IC9: HC245
    IC10, IC11: SRAM: 65256BLFP-10T
    IC12: 74AC86
    IC13: CDROM LSI: LC89515
    IC14, IC15: SRAM (CD-ROM Decoder): MB8464A-90L
    IC16: SRAM (Save Game): MB8464A-10L
    IC17: 74AC74

    When I look at this list I see more than one chip. I'm wondering if just replacing the IC16 would fix my issue or should I replace all of them while I'm doing just the one.
    I know this job is going to be a PITA as I have never tried too or attempted too remove an internal controller chip from a board. I have watched a few youtube videos on this and they make it look easy
    with the right equipment. I really don't want to put my entire life savings into getting this unit working.
    Last edited by qzack; 03-06-2014 at 09:45 AM.
    Having issues with your Game Gear..?
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    Contact me. I do capacitor replacement which will fix these issues

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    Electronics Engineer Road Rasher db Electronics's Avatar
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    https://www.dropbox.com/s/ij99nsobuh...0optimized.pdf

    According to the above schematic on page 2, the BRAM is reference designator IC10.

    This seems a bit odd to me seeing as how IC10, according to your picture, is quite far away from the Battery. I personally would've guessed at IC16 being the BRAM from the looks of your picture. However, I can't really read any of the IC markings from your picture, with the schematic in hand, you should be able to confirm that IC10 is in fact the BRAM.

    Edit:

    On page 8 of the service manual linked above, it shows that IC10, is located where IC16 is in your picture. We seem to be dealing with two different revisions here...
    Last edited by db Electronics; 03-06-2014 at 09:56 AM. Reason: More info required
    www.db-elec.com
    Code:
    do {
        Genesis();
    } while (Nintendont());

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    Electronics Engineer Road Rasher db Electronics's Avatar
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    Quote Originally Posted by qzack View Post
    I really don't want to put my entire life savings into getting this unit working.
    You should look into get a Hot Air Rework Station. You can get a pretty decent one shipped for under $100, it would make short work of lifting the surface mount SRAM chip.

    Quote Originally Posted by qzack View Post
    I'm wondering if just replacing the IC16 would fix my issue or should I replace all of them while I'm doing just the one.
    I would start by just replacing IC16 personally. Incremental troubleshooting is always best...
    www.db-elec.com
    Code:
    do {
        Genesis();
    } while (Nintendont());

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