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Thread: Trying to fix a BBC Micro (B)

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    Amibayer! dougal's Avatar
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    Default Trying to fix a BBC Micro (B)

    Hi, non-Amiga question here.

    A friend of mine gave me a BBC Micro B, has a rev 7 board. I tried hooking it up, the PSU popped and smoked.

    Before & after it popped the speaker constantly beeps - the tone of the beep different almost every time I switch it on.

    The CAPS light is stuck on.

    Composite or RF gives different displays when switched on. Either grey and jumpy screen or black and jumpy screen etc..

    I tried re-seating all the socketed chips.

    I tested the voltages: +5V is fine and -5 reads out -4.3v to -4.6v when everything is plugged into the board or else -3.somethingV when all power cables unplugged.

    If I remove IC6 (video chip ?) and switch on there is no beeping anymore.

    Any ideas ? I've never worked on a Beeb before
    A4000D '040@33mhz 16MB OS3.9 Picasso II - A2000'030@25Mhz 8Mb KS3.1 - A1200 '030@50Mhz 64Mb OS3.9 - A600 2Mb Chip + 4Mb fast ,2gb CF HD KS/WB 3.1 - A500 Plus 2mb chip + 2mb A590 + Gotek - CD32 + Analogic FDD - CDTV With joy/mouse ports

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    GurúMeditating trixster's Avatar
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    I’d recommend you join the excellent Stardot forum. The guys on there will have your problems diagnosed and fixed pretty much immediately!
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    Amibayer! dougal's Avatar
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    Thanks
    A4000D '040@33mhz 16MB OS3.9 Picasso II - A2000'030@25Mhz 8Mb KS3.1 - A1200 '030@50Mhz 64Mb OS3.9 - A600 2Mb Chip + 4Mb fast ,2gb CF HD KS/WB 3.1 - A500 Plus 2mb chip + 2mb A590 + Gotek - CD32 + Analogic FDD - CDTV With joy/mouse ports

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    Send it to Bas (theCorfiot) he's the beeb master. Unless your wanting to fix it yourself of course?

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    Amibayer! dougal's Avatar
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    Quote Originally Posted by Retro-Protect View Post
    Send it to Bas (theCorfiot) he's the beeb master. Unless your wanting to fix it yourself of course?
    I am discussing this on the Stardot forums and also been doing a lot of research of my own and using my multimeter. We are suspecting the issue is the NE555 (timer) which is keeping the reset line low (0v) on pin 40 of the 6502.

    I am going to buy a new NE555 on Monday (its only 33 cents from a local shop) and will have a go at replacing that first.
    A4000D '040@33mhz 16MB OS3.9 Picasso II - A2000'030@25Mhz 8Mb KS3.1 - A1200 '030@50Mhz 64Mb OS3.9 - A600 2Mb Chip + 4Mb fast ,2gb CF HD KS/WB 3.1 - A500 Plus 2mb chip + 2mb A590 + Gotek - CD32 + Analogic FDD - CDTV With joy/mouse ports

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