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Thread: A4000TX ATX Amiga motherboard

  1. #231
    idledk's Avatar
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    Quote Originally Posted by dorkbert View Post
    Got mine.
    That was fast.... Well, at least it seems he have (had) some.....

    Or USA might be the only country he can ship to.

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    If someone has one of the 54pin edge connectors and can ship it to the UK let me know.

    I tried to order 100 pcs from Ebay and they didn't turn up, i got told by the seller they where stopped by UK customs and because i'd refused to pay the import tax they had been returned to the seller at his cost so there would be no refund.
    Needless to say nobody ever contacted me to say that the shipment was held up by customs and that i needed to pay the import tax. i've now written this cost off but i'm still on the look out for some connectors. i had planned to offer the ones i didn't use on here at cost + shipping. but nevermind.

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    Hi just wonder on what PSU I should go for with this A4000TX board. I do not like to put a 500watt PSU in it since I belive that is just stupid but do anyone know if the board have any overcurrent protection? If there is a short it may blow more that just components, worst case tracks on the board if there is no protection. I do see some fuses but not shure what they are ment for. Hese do you have any thoughts on this?

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    Every high quality Power Supply should work, that means with Overvoltage, Undervoltage, Overcurrent and Shortcrcuit Protection.

    Even a A4000 System with 64MB Onboard Ram, CS MK1 060 (128MB), Fastlane (64MB), Picasso IV, A2386SX, AriadneII, SCSI CD Rom, CD-RW and 128GB SSD with SCSI Adapter consumes significantly less than 100W.
    But since an Amiga use almost exclusively the 5V Line 20A schould be the minimum the Powersupply can handle, the other Lines are completely uncritical.

    As a Guide the The A4000 Powersupply Specs:
    +5V 25A
    +12V 10A
    -5V 0,3A
    -12V 0,3A

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    Quote Originally Posted by dorken View Post
    As a Guide the The A4000 Powersupply Specs:
    +5V 25A
    +12V 10A
    -5V 0,3A
    -12V 0,3A
    Is -5v actually used anywhere? ATX power supplies have not had the -5v line populated in years.

  6. #236
    idledk's Avatar
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    Quote Originally Posted by dorkbert View Post
    Quote Originally Posted by dorken View Post
    As a Guide the The A4000 Powersupply Specs:
    +5V 25A
    +12V 10A
    -5V 0,3A
    -12V 0,3A
    Is -5v actually used anywhere? ATX power supplies have not had the -5v line populated in years.

    You (might) still need -5 on the Zorro bus, depending on what you insert, even though nothing on the board itself appears to require it.

  7. #237
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    A4000D power supply hasn't got -5V. There is only +5V, +12V and -12V, see spec on it. A4000D motherboard power connector hasn't got possibility to connect -5V too, so A4000D itself doesn't need it and if any card on Zorro bus require -5V it has to have it's own DC/DC converter.

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    An A4000D the -5V is generated from the -12V line with an 7905 linear regulator (U19 and two parallel 20 Ohm Resistors.
    This is a common cause of error if this line is loaded, since at 0,3A the Regulator is feed with 9V (3V voltage drop at the resistors) and generate 1,2W heat without a heatsink...

  9. #239
    idledk's Avatar
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    Quote Originally Posted by dolek View Post
    A4000D power supply hasn't got -5V. There is only +5V, +12V and -12V, see spec on it. A4000D motherboard power connector hasn't got possibility to connect -5V too, so A4000D itself doesn't need it and if any card on Zorro bus require -5V it has to have it's own DC/DC converter.

    You're right. The A4000TX have a MC7905CD2TG for generating (1A) nagative 5v.
    Hadn't seen that.

  10. #240
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    Quote Originally Posted by dorken View Post
    An A4000D the -5V is generated from the -12V line with an 7905 linear regulator (U19 and two parallel 20 Ohm Resistors.
    This is a common cause of error if this line is loaded, since at 0,3A the Regulator is feed with 9V (3V voltage drop at the resistors) and generate 1,2W heat without a heatsink...
    OK, You're right. I have missed it when I was checking it on www.amigapcb.org. But I still don't know why the spec says that the power supply has -5V.

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