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Thread: S u p e r b r a i n

  1. #1

    Default S u p e r b r a i n

    Time for an update, first of many.

    After a 4 hour drive, it's here. Superbrain. Wow, big. Yes, it has a hard drive. Probably from the Jurassic period. The interface card is attached to the right of the drive frame, where the S100 expansions normally go. It's not an S100 card.
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  2. #2

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    Inside, it is predictably filthy and the boot ROM's window is not covered. I imagine it is dead. There are genuine computer "bugs" lying in the dust. And let's not dwell on the keyboard. Eurgh.

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    I have the Y key, it has broken off at the stem. Can be glued back on I think, if I can extract the top part of the plunger from the key.

    Now for some dusting.

  3. #3

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    POWER UP

    The hard disk spins up, sounds a bit sick. Nothing else happens. I don't know if there is power to the main board yet. Te hard drive appears to have its own power supply, a toroidal transformer no less.

  4. #4

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    Signs of stress on the power board. Keyboard plate is bent, and there's an odd board under the motherboard which is part of the HDD interface.

    IMG_3851.jpgIMG_3852.jpgIMG_0814.jpgIMG_0811.jpg

    This is most weird.
    Last edited by JonB; April 8th, 2017 at 10:32 AM.

  5. #5

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    Something bad has happened here, that's for sure.

    IMG_0815.jpgIMG_0816.jpg

    There's a lot of carbonised components here. Look like diodes.

    Under the monitor plate, there appears to be another power supply, Astec model AC8233. 240v in, +12v, +5v, -5v out, 50W. There is only one output connected, it goes to the drive power socket and I assume it's the +12v. So I guess the toroidal transformer has been added to supply + -5v to provide more oomph for the HDD interface, or the original supply failed.

    I wonder if this led to the failure of the power distribution board?
    Last edited by JonB; April 8th, 2017 at 02:22 AM.

  6. #6

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    Hard drive controller is "act 5MSDC REV-1" and its daughter card is labelled "act HOP-0". Plot thickens.

  7. #7

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    Tasty Tandon drive is double sided.

    HDD is anonymous.

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    Looks very ST-506? The crackle finish was flaking off the faceplate so I removed it.

  8. #8

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    Now we can see how the factory power supply has been modified. Thick brown and blue are the 240v connections. Thin blue is the +12v (assumed). They used automotive crimp connectors, what a bodge.

    IMG_0826.jpgIMG_0827.jpg

    The ribbon cable between the serial / power distribution board and the motherboard is soldered in. And it looks like it is going to break any time soon.

    IMG_0828.jpg

    It's a swine, because I would like to unplug it to concentrate on the power supply, but that is not possible unless I desolder the thing.

    [edit: Actually, it isn't soldered in. I was desoldering it from the motherboard and it came out (of its low profile SIL socket).]
    Last edited by JonB; April 8th, 2017 at 10:00 AM.

  9. #9

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    The power supply board is now out and I am examining it. It's an Intertec board with part number 5002020 Rev 3. Naturally a Google search turned up nothing.

    The PCB is burned through and there are missing tracks. I think the transformer is salvageable but the two components that caused the damage (a ceramic disk capacitor which must have exploded from the look of it and what appears to be a resistor or diode, except it is just a melted blob of carbon now) are utterly toasted.

    There is a third part, a resistor, which survived albeit in a blackened state and I think the colour code is Black (impossible?) Brown Orange. I think it is toast, it is measuring as 129 Ohms! It's big-ish, probably 2 or 3 Watt.

    Close up of the site of the explosion. Looks bad, but there are only three components to wire up plus the transformer.

    IMG_0835.jpg

    Removed parts: Top: transformer, middle: blob of carbon, bottom: exploded ceramic capacitor.

    IMG_0836.jpg
    Last edited by JonB; April 8th, 2017 at 10:29 AM.

  10. #10

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    IMG_0837.jpg

    The mystery solved, after a good look at the schematics.

    I'll put R2 back in as it is in tolerance at 129ohms. R1 and C6 on order! Then I can rebuild the circuit and test it.

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