So wanting to replace my old and trusty original A4000 PSU with A4000 ATX PSU power adapter I purchased a micor-ATX psu that fits nicely into the A4000 PSU chasis BUT....

1-tried connecting micro-ATX and nothing..PSU not starting at all nor A4000 so tried another dull size ATX PSU and same thing
2- contacted Amigakit and they told me it was some 'sense' thing with newer PSU's but I had my suspicions
3- tried starting the PSU without connecting to A4000 and voila PSU started up no problem with following voltage readings:

Grey (what you call purple)-+5.21v
Blue--11.32v
Yellow-+ 12.14v
Red-+5.23v
4- let Amigakit know and they said these readings were fine and adapter was working ok but offered no help as to why it wasn't powering on my A4000

So long story over I turn this mystery over to my fellow amigans and hopefully I'm not the only one in the world this has happened too?&^! ..how come this kinda luck never happens when I buy a lottery ticket

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c64-2sids, A1000, A1200T-060@50(finally working!),A4000-CSMKIII
! My Master Miggies- Amiga 1000 & AmigaOne X1000 !
mancave-ramblings
X1000 I BELIEVE

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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c64-2sids, A1000, A1200T-060@50(finally working!),A4000-CSMKIII
! My Master Miggies- Amiga 1000 & AmigaOne X1000 !
mancave-ramblings
X1000 I BELIEVE

@klx300r

What ATX power supply do you use resp. what's its power rating for the outputs?

Over on a1k.org Matze developed a more sophisticated ATX power supply adapter for classic Amigas that can also put some load on the 12V line as modern ATX power supplies seem to expect most load on this line (because of the CPU voltage regulators connected to 12V - contrary to Amigas, which have most load on the 5V line).

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@klx300r

I don't know what you did and what you missed to do.

But many modern PC Power Suplys won't start up without a proper modification.

Look here: https://www.instructables.com/id/How-to-power-up-an-ATX-Power-Supply-without-a-PC/

So if you know all this details, have you checked the output voltages with a voltmeter?

Last edited by OneTimer1 on 11-Aug-2019 at 06:12 PM.