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AuthorTopic: need help my A4000 won't start with new A4000 ATX PSU adapter  (Read 1205 times)

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Offline dalek

Re: need help my A4000 won't start with new A4000 ATX PSU adapter
« Reply #15 on: July 25, 2019, 01:02:06 AM »

* -5V is not needed on the Amiga
* always test voltages with a dummy load applied - you can't assume the voltages of an unloaded supply are 'in spec'

Also check the 3.3V Sense wire - apply a dummy load the 3.3V line and also connect it to the Sense wire - more info here: https://reprap.org/wiki/PC_Power_Supply#Voltage_Sensing


 

Offline Darin

Re: need help my A4000 won't start with new A4000 ATX PSU adapter
« Reply #16 on: July 25, 2019, 05:42:26 PM »

* -5V is not needed on the Amiga
* always test voltages with a dummy load applied - you can't assume the voltages of an unloaded supply are 'in spec'

Also check the 3.3V Sense wire - apply a dummy load the 3.3V line and also connect it to the Sense wire - more info here: https://reprap.org/wiki/PC_Power_Supply#Voltage_Sensing

I'll disagree on the -5v being needed, as -5v runs though the video slot, the Zorro slots, and the RGB connector. 

I will agree that it is best to test the voltages with a PSU under load.
 

Offline dalek

Re: need help my A4000 won't start with new A4000 ATX PSU adapter
« Reply #17 on: July 26, 2019, 03:15:09 AM »
I'll disagree on the -5v being needed, as -5v runs though the video slot, the Zorro slots, and the RGB connector. 

I should have been more specific.  It's not needed to be supplied by the PSU to the A4000.  If you tell him he needs -5V from his ATX PSU that is wrong.

-5V on the A4000 is generated from -12V on the motherboard.  So it is not needed to be supplied by the ATX PSU he has.

Offline Darin

Re: need help my A4000 won't start with new A4000 ATX PSU adapter
« Reply #18 on: July 26, 2019, 05:02:43 PM »

I should have been more specific.  It's not needed to be supplied by the PSU to the A4000.  If you tell him he needs -5V from his ATX PSU that is wrong.

-5V on the A4000 is generated from -12V on the motherboard.  So it is not needed to be supplied by the ATX PSU he has.

Ah!!  Yeah, there are two topics in this thread...  One is on the A4000 PSU replacement, which yeah totally, the A4000 PSU doesn't supply -5v.  Which makes it much easier to use an ATX PSU with an A4000 as long as the PSU can supply enough current for the A4000.

The other topic that was brought up was an A3000 ATX PSU adapter and how modern ATX PSUs don't supply the -5v that the A3000 needs.  My previous comment was directed at the A3000 and it having -5v from the PSU.
 

Offline F1Lupo

Re: need help my A4000 won't start with new A4000 ATX PSU adapter
« Reply #19 on: August 11, 2019, 05:10:09 AM »

yup mine thankfully still starts up with original PSU


Oh, that's good!   I would try to find an ATX power supply where the blue line for -12V is more in the range of -11.8V to -12.2V.  The -11.32V your getting there may be too low for your A4000.
Update:
got around to try a full sized ATX PSU tonight and readings as follows when not connected to anything again:
Grey -+5.11v
Blue--11.52v
Yellow-+ 12.21v
Red-+5.11v
and yet again like the micro-ATX PSU my A4000 won't boot up at all. Tried attaching an old 'real' hard drive to see if some extra load draw would kick it up but same thing. :(
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Offline tonyvdb

Re: need help my A4000 won't start with new A4000 ATX PSU adapter
« Reply #20 on: August 12, 2019, 03:32:19 PM »
Ok its been years since Ive put my ATX power supply in my Amiga 4000 but if I remember correctly doesn't the ATX power supply need a jumper between two of the pins on the ATX connector in order to turn it on? I built my own adapter for it and my 4000 has been running fine on it for years.
Also are you sure that all the pins are actually connecting in the Amiga 6pin connector? I bought one way back on ebay and it never worked either untill I found out that one of the pins wasnt even connecting to the other inside the connector.
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