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Author Topic: A2000 ATX PSU Power Adapter Cable [ADAPSU010] > what about -5V ?  (Read 906 times)

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Offline RetroNinjaTopic starter

A2000 ATX PSU Power Adapter Cable [ADAPSU010] > what about -5V ?
« on: September 19, 2023, 11:32:22 PM »

For AmigaKit's power supply cable:

A2000 ATX PSU Power Adapter Cable for Amiga 2000
[ADAPSU010]

Does anyone know if the ATX power supply has to have a -5V line? Or, does this cable convert a spare +5V to -5V? Another way to say the same thing, is there any intelligence in this adapter or is it just a straight through cable converter?
 

Offline Castellen

Re: A2000 ATX PSU Power Adapter Cable [ADAPSU010] > what about -5V ?
« Reply #1 on: September 20, 2023, 08:17:59 AM »
From the photos online it's a passive cable that appears to connect -5V from the ATX supply to -5V on the A2000 connector (white wire).

https://www.amigastore.com/a2000-power-adapter-cable-amiga-2000-p-998.html

It's fairly rare to see much that uses -5V.  All I can think of is a few older Zorro 2 expansion cards and video processing expansions.  The A2000 itself will operate fine without the -5V supply.
 

Offline RetroNinjaTopic starter

Re: A2000 ATX PSU Power Adapter Cable [ADAPSU010] > what about -5V ?
« Reply #2 on: September 20, 2023, 05:45:10 PM »
Huh, I was under the impression the A2000 needed for the -5V for the boot process. Thanks for the info.
 

Offline Castellen

Re: A2000 ATX PSU Power Adapter Cable [ADAPSU010] > what about -5V ?
« Reply #3 on: September 20, 2023, 09:02:09 PM »
I was under the impression the A2000 needed for the -5V for the boot process.

The A2000, as with other Amigas, only needs +5V to boot normally.  If you want audio output and RS232 serial, then you need both +12V and -12V as well.  Most floppy drives and mechanical hard drives need both +5V and +12V.

The A2000 also needs the 50Hz/60Hz tick signal that normally comes from the power supply.  It won't boot without it as this timing reference increments some of the hardware timers.  For non-original power supplies that don't provide the 'tick' signal, you can change main board jumper J300 from external to internal which drives the timer from an internally derived signal instead.