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  • BNOS 12A 13.8V PSU

    From G8MNY@21:5/101 to TECH on Fri Jun 28 06:30:08 2019
    R:190628/0921Z 31762@N3HYM.MD.USA.NOAM BPQ6.0.18
    R:190628/0928Z @:GB7CIP.#32.GBR.EURO #:10235 [Caterham Surrey GBR]

    From: G8MNY@GB7CIP.#32.GBR.EURO
    To : TECH@WW

    By G8MNY (New Dec 12)
    (8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

    I have repaired some these, the 12A (15A meter) & 30A model are similar. ┌───────────┐
    │ ┌─────┐ │ Current limiting
    │ │\ │ │ Over voltage Crowbar @ 14.5V
    │ │ \ │ │
    │ └─────┘ │
    │ │
    │ o o │
    └┬┬──────┬┬─┘

    INPUT CIRCUIT
    The mains transformer's 2 secondaries feed a bridge rectifier & then to the capacitor bank. (the bridge can fail on heavy use)
    __ ___________________
    L─o-o──o\─┐||( \__ / │+ │ │+ +20V
    3A )||(_ / Single === │+ ===
    )|| _X Bridge │ === │3x
    )||( \_Rectifier │ │ │6m8
    N─────────┘||(__/ \ \__│___│___│________-Ve (0V)
    E──┐ 2x 17V 10A \ \
    \ └┤>├─┬┤>├─180─┬───┬───┬─+24V
    \AC │ │+ _│_ │u1
    └─┤├─┘ === /_\'=== ON PCB
    + │ │24V│
    └───┴───┴─0V
    CONTROL CIRCUIT
    +20V┬─────────┬────┬──────────┬──────┐
    │ │/ │ │/ │/ 2x
    ┌─┬───)───┬───┤TIP120│ ┌───┼───┬──┤ 2N3055
    │ │ │ │ │\e │/ │ │\e │ │\e PASS
    │ │ │ _│_ └──┤ ├─┤├──┤ └┤├──┤TRANSISTORS
    │ │ _│_ \_/ │\e │ │ R
    │ │ /_\ │ Driver └────┤ ┌─1k┴──R───┴────────────────(Amp)─┬─>+13.8V
    │ │ │ ├───────────────)─)───────────────────2k2──┐ │
    │ │ ├───)────┬──────────)─)─────┬───────────┬──────)──┬──┬──┤
    │ │ │ │ │ │ │ │ _│_ _│_ │u1│ │
    +24V │ │ │ │ │ ┌SETI──)─┘ │ \_/ =\_/ │ === │
    ├─┐ │ │ │ │ │ │/e │ ┌5k1─┤ │ red│ │ │ _│_
    2│3│8│1│ │ │ └─┤PNP u1│ │ ┌──┴───┐8 ├──────┤ 1K │ /_\
    ┌┴─┴─┴─┴┐ 18k │ │\ === ├─┤MC3423├─┐ SCR_│_ │ │ │ │
    │ LM376 │ │ \│ │ │ │2└┬─┬─┬┬┘ │ \_/ _│_ │ │ │
    └┬─┬─┬─┬┘ SET NPN├─┬2k2┬┴──┐ │ │ 1│8│4││3 │ /│ =\_/ │ │ │
    4│5│7│6└┬─>V e/│ │ │+ │ │ 1k ├─┘+├┘ +├100┤ │ Green│ │ │ │
    │===└┤├┘ │ │ === === 10K │ │ │ === === ===│ 2k2 │ │ │
    │ │u1 2K2 │ u1│ │10u│ │ │ │10u│10u│ u1│ │ │ │ │ │
    ──┴─┴───────┴───┴───┴───┴───┴───┴──┴──┴───┴───┴───┴─┴──────┴──┴──┴──┴─>0V
    Volt Control Current Limit Over Voltage Crowbar

    VOLTAGE CONTROL
    The voltage control IC LM376 runs on a voltage doubled supply of 24V. It compares it's internal reference with the preset SET V & drives the TIP120 darlington to drive the 2 heat sinked pass transistors to maintain the output voltage.

    CURRENT LIMITING
    The 2 pass transistors have current equalising emitter resistors (R), & when one of these is over the base emitter voltage of the PNP, that turns on a NPN to override the LM376 drive, to limit the current.

    OVER VOLTAGE PROTECTION
    IC MC3423 is a triggered over voltage IC that fires the crowbar SCR to short the output if it is too high. Danger here is when charging batteries if the trip should go causing a fire. So use a fuse with battery!


    Why don't U send an interesting bul?

    73 De John, G8MNY @ GB7CIP


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    * Origin: HAMRADIO telnet lu9dce.dynu.com (21:5/101)