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Thread: A4000 PSU

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    Default A4000 PSU

    Hello.

    I need an A4000 PSU in perfect working order, if possible with a silent fan already mounted.

    Thanks.
    A4000/CSMKII60/C643D/Deneb/CatWeasel/A2386/STBNitro/SB16/MT32
    A500+/Viper520CD/KCSPowerPC


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    I could also use some help about buying an ATX replacement along with the adapter from amigakit.



    It seems that 12,5 cm wide PSU might fit the A4000 case screws but would leave space underneath, like this one:



    How to fit it securily?

    And more important, would the PSU actually turn itself off with the switch from amigakit?

    I do not like those ATX PSU that are always on.
    I ahae not owned a PC tower since the AT era with good old power switch, only laptops, and i am not confotable with the ATX standard.
    A4000/CSMKII60/C643D/Deneb/CatWeasel/A2386/STBNitro/SB16/MT32
    A500+/Viper520CD/KCSPowerPC


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    Yes, it will turn itself off (output section).

    For completely turning off you may have to find one with an ON/OFF switch on the back. Only very good ATX PSU models have this switch.

    For the space, see this awesome thread: Keropi's approach look this way.
    David Bradley made Ctrl+Alt+Del, Gates turn it mandatory
    16 Amigas at home :D
    3x C= 64 :smile:
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    8 PC (argh) :thumbsdown: at least one is an AROS/Amithlon unit

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    Great link thanks.

    Would you have any specific good PSU with a switch at the back to recommend?
    A4000/CSMKII60/C643D/Deneb/CatWeasel/A2386/STBNitro/SB16/MT32
    A500+/Viper520CD/KCSPowerPC


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    Not from Europe, I'm afraid. You need to ask the locals.

    Just remember those newest ATX24 connector units needs around 15 to 20% of the 3.3V rail maximum rate to work properly or they will not regulate the other voltages.

    Be warned, although a high wattage simple resistor will do the trick ( 0.47 Ohm x 50W soldered directly inside the PSU to keep the resistor cold).
    David Bradley made Ctrl+Alt+Del, Gates turn it mandatory
    16 Amigas at home :D
    3x C= 64 :smile:
    1 VIC-20 :smile:
    8 PC (argh) :thumbsdown: at least one is an AROS/Amithlon unit

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    The best PSU i have found so far is the ADVANCE Micro ATX - 120x125x63mm - PX-3300P08 -300W


    It has a 125 mm width, a power switch but may be to weak on the +5V at only 12 A.

    + 3.3 V: 20A
    + 5 V: 12A
    + 12 V: 20A
    - 12 V: 0.5A
    + 5.5 V Sb: 1.5A
    Vitesse ventilateur 1200 tr/min
    Entrée: 115/230V

    What do you think?

    MicroATX PSU with more than 20A on the +5V are a lot bigger.

    By the way, would someone have an original A4000 PSU handy to give me the exact dimensions?


    A4000/CSMKII60/C643D/Deneb/CatWeasel/A2386/STBNitro/SB16/MT32
    A500+/Viper520CD/KCSPowerPC


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    On this specific PSU you need a charge of 4A on the 3.3V rail to stabilize the other voltages, so this means a 0.82 Ohm resistor (good luck finding one!) per 10W dissipation at least.

    If you don't find one, use TWO 1 Ohm /10W resistors IN PARALLEL to draw ~ 6.6A from the rail. This will suffice to force the PSU to regulate the other voltage rails to safe Amiga operation.

    Just don't use much Zorro cards on this Amiga because the relatively weak +5V rail.

    Now, if you can measure the A4000 PSU height & width you may find something better who fits on the available space.
    David Bradley made Ctrl+Alt+Del, Gates turn it mandatory
    16 Amigas at home :D
    3x C= 64 :smile:
    1 VIC-20 :smile:
    8 PC (argh) :thumbsdown: at least one is an AROS/Amithlon unit

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    Well, unfortunately, i won't be able to add any resistor myself. For such a work, i can only count on Cosmos, who lives 400 km far from me. Sending him all my parts has already drained so much money from my pocket in shipping cost that i could buy another A4000.

    I need to find a good enough PSU at once or find someone to build a better one for me.

    The A4000 is rather limited in slots, unlike the A2000. Would 4 zorro boards and 2 ISA boards be too much?

    Could you explain a bit more the concept of charge on the 3,3V? I do not understand what it means. Is the 3,3V used on the amiga?
    A4000/CSMKII60/C643D/Deneb/CatWeasel/A2386/STBNitro/SB16/MT32
    A500+/Viper520CD/KCSPowerPC


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    The 3.3V is not used by the Amiga at all unless you are using a hacked Meditator 4000Di and a Radeon92xx.

    In order to make ATX stabilizes ALL their voltages, some charge (consumption) must be put on the 3.3V wires. That's where the pair of 1 Ohm x 10W resistor goes. Without they the 3.3V will not have any consumption, rendering the whole power brick VOLTAGES unstable.

    But of course you can add those resistors directly on the ATX connector, just notice the pair will heat a lot. You also must make they secure in the socket.

    Four Zorro boards and two ISA will consume a lot of juice, prefer to find something with at least 28A on the +5V rail for secure operation.
    David Bradley made Ctrl+Alt+Del, Gates turn it mandatory
    16 Amigas at home :D
    3x C= 64 :smile:
    1 VIC-20 :smile:
    8 PC (argh) :thumbsdown: at least one is an AROS/Amithlon unit

  10. #10
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    I understand now
    Do you think that the Amigakit adapter does the 3,3V trick?

    I have mailed Amigakit already about this adapter but i have no answer.
    A4000/CSMKII60/C643D/Deneb/CatWeasel/A2386/STBNitro/SB16/MT32
    A500+/Viper520CD/KCSPowerPC


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