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Thread: SB 2.0, CT1336A, and CMS upgrade

  1. #11

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    Quote Originally Posted by Robin4 View Post
    You are using a different OPL3 DIP chip? Because the original is 3812.
    FM1312 is just an OPL2 (YM3812) with a label.
    OPL3 (YMF262) were first used by Creative in SB Pro 2, CT1600.

  2. #12

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    Quote Originally Posted by rado View Post
    Also, there is a very simple fix to make the SB 2.0 compatible with systems without the −5V power line.
    So, SB 2.0 needs -5V?
    That would be one more surprise from that card - I thought -5V was only for stuff like i8080 cards and similar 1970s gear...

    Quote Originally Posted by BloodyCactus View Post
    no, creative put those FM1312 stickers on the chips a lot back then for some reason.
    Indeed, there's no special meaning about those Creative stickers.
    Philips SAA1099 with "CMS-301" sticker is still normal Philips SAA1099, and Yamaha YM3812 (OPL2, not OPL3 !) with "FM1312" sticker is still normal Yamaha YM3812.

  3. #13

    Lightbulb

    Quote Originally Posted by Xacalite View Post
    So, SB 2.0 needs -5V?
    That would be one more surprise from that card - I thought -5V was only for stuff like i8080 cards and similar 1970s gear...
    Yes, NMOS technology usually comes to ones mind.
    But there are many cards using opamps which require symmetric power supplies. For example, the CT1350B SB2.0, the CT1920 AWE32 Upgrade and the Roland LAPC-I, all of them require −5V.
    The SB2.0 may easily be fixed by adding one resistor between the −5V and the −12V line:
    Attachment 50516
    Of course, it is not an ideal solution, but at least it is not destructive. The opamp doesn't mind if it is powered somewhat assymetrically.
    If there is another card requiring −5V present in the system, a different solution should be considered.

  4. #14

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    Quote Originally Posted by rado View Post
    Y
    The SB2.0 may easily be fixed by adding one resistor between the −5V and the −12V line:
    your attachment is broken, but you need TWO resistors for a voltage divider network.

  5. #15

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    Quote Originally Posted by BloodyCactus View Post
    your attachment is broken, but you need TWO resistors for a voltage divider network.
    A voltage divider would be fine, but the SB2.0 works equally well if you feed it with −12V instead of −5V.
    The simplest fix is to cut the trace from the −5V ISA power line and to connect the negative power supply pins of the opamps directly to −12V.
    But I don't like cutting traces and so I've added a 390Ω resistor between the −5V and −12V power lines. Not an ideal solution, but better than cutting. Quite acceptable when the SB2.0 is the only card requiring −5V.

  6. #16

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    Quote Originally Posted by rado View Post
    But I don't like cutting traces and so I've added a 390Ω resistor between the −5V and −12V power lines. Not an ideal solution, but better than cutting. Quite acceptable when the SB2.0 is the only card requiring −5V.
    so your pumping -12V into the entire motherboard's -5V line? A resistor in series will change its voltage based on the current drawn. I dont know what a 390ohm resistor will really be doing for you, but it shouldnt matter much, the -12 and -5v line have so little current available anyway.

    mostly I just dont like the idea of passing -12 straight into the -5v line and making it available to the entire system

    if the opamp can take -12 it will probably sound better than with -5 anyway!

  7. #17

    Smile

    Quote Originally Posted by BloodyCactus View Post
    so your pumping -12V into the entire motherboard's -5V line? A resistor in series will change its voltage based on the current drawn. I dont know what a 390ohm resistor will really be doing for you, but it shouldnt matter much, the -12 and -5v line have so little current available anyway.

    mostly I just dont like the idea of passing -12 straight into the -5v line and making it available to the entire system

    if the opamp can take -12 it will probably sound better than with -5 anyway!

    I fully agree with you. Fortunately, I know exactly what I am doing. All the 100% correct solutions require cutting traces or at least using a tape to isolate the −5V line and I don't like that. I have already explained my reasoning behind the decision.

    If the power supply provides −5V, then there is absolutely no problem, as the additional current between the negative lines would increase only by 18mA. They are regulated anyway.
    If the power supply doesn't provide −5V, then the other system components don't utilize the line.
    In a scenario when one would put two or more ISA cards requiring −5V into a system without the −5V line, any damage would be very-very unlikely.

  8. #18

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    Is the lack of -5V a common problem?
    Anyway, I would rather modify the power supply, not the card.

  9. #19

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    Quote Originally Posted by Xacalite View Post
    Is the lack of -5V a common problem?
    Anyway, I would rather modify the power supply, not the card.
    Yes, many ATX power supplies do not provide that voltage.
    If you are skilled enough, you may add an 7905 voltage regulator with 2 caps, but for many people tampering with the power supply would be too risky.

  10. #20

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    Quote Originally Posted by rado View Post
    Yes, many ATX power supplies do not provide that voltage.
    Good to know!
    While I keep cards like SB 2.0 for machines many years earlier than ATX, I may occasionally test them in some ATX box.
    Note to self: if such a card fails to work with ATX, it doesn't necessarily mean it's broken, remember to check the -5V line as well!

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