Repairing a machine pin/trace; finding +5VDC (newbie)

Discussion in 'Electronics & Electrics' started by bYrd, Feb 17, 2017.

  1. bYrd

    bYrd Member

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    Hi,

    I picked up an Amiga 1200 with a faulty 44 pin 2.5" IDE connector, notably broken/snapped pin 44 (type 0-ATA) and pin 42 (+5VDC logic). It appears the pins were weakened due to nearby leaking caps - the caps look like they were replaced. The 2.5" IDE header was also replaced, poorly, and I wouldn't like my chances of desoldering this and replacing the entire header. I'm keen to run a CF to IDE card off this.

    As the broken machine pins were too short to grab, I had to use a scalpel to cut back the plastic support so I could just grab each broken pin with fine pliers, while desoldering.

    All out, pin 44 was replaced easily enough (type 0-ATA) but pin 42 looks rough with the pad missing (+5VDC logic). The adjacent pin to this is ... pin 41 +5VDC (motor) ... is it feasible for me to source +5VDC from here? Or is it better for me to source +5VDC from elsewhere (such as the Amiga floppy connector)?

    Thanks - excuse the newbie question, I've not done this sort of trace level repair before.

    JB
     
    Last edited: Feb 17, 2017
  2. SLATYE

    SLATYE SLATYE, not SLAYTE

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    I'd be surprised if there were separate 5V power supplies for motor and logic, so it should be safe to share them - but probably best to wait and see if someone has specific knowledge of the system.

    If you can trace the track from where the pad used to be, you should be able to find a component that it connects to (and it'll also be obvious if it connects to the 5V motor pin). Capacitors are always a good bet; there's sure to be several of those on any power supply trace. If you can find one close, it's easy to solder a wire from the appropriate terminal to the new pin.

    From the picture I've just found, C239 (right next to the connector) would be a likely candidate - it's probably handling either motor 5V, logic 5V, or both. If it's logic 5V then you can take the + pin from there as your supply. If it's both, then you can share logic and motor 5V. If it's just motor 5V, then you need to find somewhere else to connect.
     
  3. rainwulf

    rainwulf Member

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    you will find motor and logic 5 volt rails might originate in the same place, but are run seperately and decoupled seperately to prevent noise from migrating down the power rails.

    However, if you dont have a motor, just use the 5 volts.
     
  4. bYrd

    bYrd Member

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    Thanks SLATYE and rainwulf,

    This was just the advice I needed to be more confident in pulling off this repair.

    Checking continuity, pins 42 (+5VDC logic, the damaged site) and pin 41 (+5VDC motor) are shared, but are probably separate (can't trace easily as it's a 4-layer PCB).

    Since I'm only going to use a CF card, I'll try this method and if issues arise, will trace from capacitor C239 as SLATYE suggested - this is connected to +5VDC logic.
     

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