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Thread: MV1C problem with battery

  1. #1
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    MV1C problem with battery

    I made the battery mod on a MV1C board that I purchased recently, and realise that everytime I turn on the board, no data is store (highscores, unibios config, etc ...)

    I did not check how the board was doing presiously with the old stock rechargeable battery.

    I use a brand new CR2032 (3,2 V), and still it doesn't work.

    I've tried to erase the backup memory (putting all switches ON for 2 minutes, and then turn off and turn on).

    Same result.

    Today I've checked the voltage, and it's 1,3V (more than half of it's caspacity drained in just 1 day, without using the board).

    Any ideas?

    pd: I used the tutorial on jamma-nation X
    Last edited by littlecharlie; 05-18-2019 at 10:32 AM.

  2. #2
    Shigen's Fitness Trainer
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    This is the problem with the MV1C, the backup ram circuit leaks current which kills the battery.

    Every MV1C I've come across has had this issue, I've heard that the C3 in the backup area under the pad sometimes goes bad and holds the circuit open which drains the battery. But I've never tried replacing it.

  3. #3
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    Quote Originally Posted by littlecharlie View Post

    Any ideas?

    pd: I used the tutorial on jamma-nation X
    Are you using a ML2032 or a CR2032 battery? Have you altered the board in any way?

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    Quote Originally Posted by Niko View Post
    This is the problem with the MV1C, the backup ram circuit leaks current which kills the battery.

    Every MV1C I've come across has had this issue, I've heard that the C3 in the backup area under the pad sometimes goes bad and holds the circuit open which drains the battery. But I've never tried replacing it.
    But my guess is that something, besides the issue you mention, is wrong. Because with a new battery, it still doesn't work.

    Quote Originally Posted by Whippy View Post
    Are you using a ML2032 or a CR2032 battery? Have you altered the board in any way?
    It's a CR2032. I followed the jamma nation tutorial, and removed R36, D5 and D6 components (to disable the charging circuit).
    I checked the circuit afterwards, and seems OK.

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    Is the new battery a good quality one? I ask because once or twice I purchased cheap CR2032 batteries from China (dubious quality of course), sometimes there would be a sharp voltage drop after a couple of days just like it happened to you, then I purchased original Panasonic batteries from mouser.com and never experienced another voltage drop like this.

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    All I can say is double check the mod.

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    I think you'd need to use a much beefier battery to hold a charge on those boards. Something like this.
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    Quote Originally Posted by Abelardo View Post
    Is the new battery a good quality one? I ask because once or twice I purchased cheap CR2032 batteries from China (dubious quality of course), sometimes there would be a sharp voltage drop after a couple of days just like it happened to you, then I purchased original Panasonic batteries from mouser.com and never experienced another voltage drop like this.
    I use SONY CR2032. I use them also in other MVS boards (MV1F and MV1FZ) with no problems.

    Quote Originally Posted by Neo Alec View Post
    All I can say is double check the mod.
    I'll re-check more deeply, you never know.

    Quote Originally Posted by daskrabs View Post
    I think you'd need to use a much beefier battery to hold a charge on those boards. Something like this.
    Yep, maybe, will try to find one here.

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    Another question.

    Can you help me locate the backup RAM on the board, and hopefully the pin where the 3V goes?

    I've made a screenshot of a video posted on the internet (this is not my board).



    -----

    Well, i guess it's both CXK58257AM and CXK58257BM.
    According to datasheet Vcc is pin 28 (top left), and should be 5V.

    Should the 3V from the battrery go to these 28 pins?
    Last edited by littlecharlie; 05-23-2019 at 02:29 PM.

  10. #10
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    ram 2 and ram 4 would be the back up ram.
    I'm getting the connection on pin 14 @ chip U3, the HC32
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    Last edited by BIG BEAR; 05-23-2019 at 07:13 PM.
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  11. #11
    Cheng's Errand Boy
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    Quote Originally Posted by littlecharlie View Post
    Another question.

    Can you help me locate the backup RAM on the board, and hopefully the pin where the 3V goes?

    I've made a screenshot of a video posted on the internet (this is not my board).



    -----

    Well, i guess it's both CXK58257AM and CXK58257BM.
    According to datasheet Vcc is pin 28 (top left), and should be 5V.

    Should the 3V from the battrery go to these 28 pins?
    It's a bit off topic but I got my MV1C like a year ago and the original battery came with it, working fine and nice looking. I've purchased some batteries like the one in the pic but didn't replace the original one with the gren new ones because I didn't know at the time if it was really mandatory. Would yo go ahead and dismantle the CMVS again to do the battery swap or do you think there's no need for that?

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    Quote Originally Posted by Hawwa View Post
    It's a bit off topic but I got my MV1C like a year ago and the original battery came with it, working fine and nice looking. I've purchased some batteries like the one in the pic but didn't replace the original one with the gren new ones because I didn't know at the time if it was really mandatory. Would yo go ahead and dismantle the CMVS again to do the battery swap or do you think there's no need for that?
    Does your MV1C have a battery holder already? If not then it has the original battery and it's most likely dead by now, no harm in simply removing it to avoid the risk of leaking and thus damaging the board.

  13. #13
    Cheng's Errand Boy
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    Quote Originally Posted by Abelardo View Post
    Does your MV1C have a battery holder already? If not then it has the original battery and it's most likely dead by now, no harm in simply removing it to avoid the risk of leaking and thus damaging the board.
    Well it has the original battery but works fine, keeps date, options and High Scores for long (longest I've been without playing was 10 days). Hence the question.

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    Quote Originally Posted by Hawwa View Post
    Well it has the original battery but works fine, keeps date, options and High Scores for long (longest I've been without playing was 10 days). Hence the question.
    If it's working and in good shape I wouldn't worry much about it, once it stops working it's time to pull it out before it leaks.

  15. #15
    Cheng's Errand Boy
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    Thanks for the tip. I'll do that and keep an eye on the battery in order to change it before it starts leaking.

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    Quote Originally Posted by BIG BEAR View Post
    ram 2 and ram 4 would be the back up ram.
    I'm getting the connection on pin 14 @ chip U3, the HC32
    BB
    I've checked and apparently the diode that was connecting the +3V and the RAMS was not working.
    So I've bypassed the diode, and now the +3V goes to the pin you mentioned on the HC32. Actually, it feeds every RAM on the back up area (not just the HC32).

    I thought this will solved the problem, but it doesnt.
    Still the same problem ...

  17. #17
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    I thought I'd revive this thread as it doesn't appear a solution was found. I am now working on an MV1C as well and I have the same issue. With the completed battery mod, the new, non-rechargeable battery appears to be dying FAST....like same day fast. My gut instinct told me that the charging circuit was still "charging" even though I removed the 3 required components (R36, D5 and D6).

    Quote Originally Posted by Niko View Post
    Every MV1C I've come across has had this issue, I've heard that the C3 in the backup area under the pad sometimes goes bad and holds the circuit open which drains the battery. But I've never tried replacing it.
    I think this suggestion is probably the solution. As a test, I removed my CR2032 battery from the holder I installed and then powered on the board. I hooked up my multimeter up to the positive and negative leads and it was receiving 3.6 volts. I have yet to try and trace back where this voltage is coming from, but if I'm not mistaken, there should be NO voltage on this circuit if the battery is removed AND the charging circuit was removed, right?

    If C3 ends up being the issue, does anyone know what resistor is supposed to be there? I was thinking of trying to replace it to see if that does anything, but mine is pretty dark so I can't read any numbers off it.

  18. #18
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    C3 is a 0.1uf capacitor in a 0805 package. Also, check the biasing on D3 and D4.

    These components also contribute fast battery drain:

    PC10 - 0.1uf cap (0612 package)
    U3 - 74HC32 (SOP8)
    RAM2/RAM4 - 256kx8 sram (SOIC28)
    Last edited by shadowkn55; 03-04-2020 at 11:05 PM.

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    Thanks! I'll be looking closer at all these components probably this weekend. As for my theory, am I correct to assume that when the board is powered up and there is no battery in the battery holder, there shouldn't be 3.6 volts between the positive and negative leads?

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    Quote Originally Posted by ledfrog View Post
    Thanks! I'll be looking closer at all these components probably this weekend. As for my theory, am I correct to assume that when the board is powered up and there is no battery in the battery holder, there shouldn't be 3.6 volts between the positive and negative leads?
    Correct. If you removed the right components, the positive and negative terminals of the battery holder should read zero volts with no battery installed.

  21. #21
    JammaNationX
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    Remove C3, sometimes it’s a parasitic part and drains the battery, weird thing is it only affects certain boards.

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    Interestingly, I was checking solder joints around C3 and it was so brittle, it basically fell apart so it's now gone anyway. I didn't get a chance to go much further, but as suggested before, I did check the biasing on D4 and D3 and they seem to be only sending voltage in one direction so I think those components are working right. I'll have to check everything again because even with C3 gone, I was still getting 3.6V sent to the positive side of the battery.

  23. #23
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    I just find this thread. I have 2 MV-1C with the exactly the same issue. It will be great to find a solution. I will try to remove C3 and report the result.

  24. #24
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    After removing C3, my results didn't change. When powering up the board, I'm still reading 3+ volts across the battery terminals, so there is juice coming from somewhere else...could possibly be deep inside the board since I think these units are multi-layered. My new plan was to acquire a replacement MV1C and start comparing readings around all the components to see if I can trace where the problem is coming from. Hopefully that new board doesn't suffer the same issue.

  25. #25
    JammaNationX
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    Are you testing voltage without a battery?

    This is also the reason why I just gave up using non-rechargeable batteries in my CMVS. It was just easier to use a rechargeable one.
    Last edited by Xian Xi; 03-18-2020 at 02:34 PM.

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