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Old 15 September 2007, 16:32   #1
Calgor
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ATX Power Supply for A4000T

Just wondering what ATX power supplies anyone has successfully used with the A4000T? Reason I ask is because while there are tons of power supplies out there, the A4000T appears to require -5V supply unlike other amigas, which most of the name brand power supplies do not offer.

In fact, I have only been able to find 1 name brand PSU, which just happens to be one of the most expensive too, the PC Power and Cooling Turbo-Cool 510 series:

http://www.pcpower.com/products/view...hp?show=T51SLI

The only other ones supplying -5v seem to only be the very cheap and nasty supplies funnily enough. What gives?

With these newer beefier supplies, there are also issues of minimum load requirements (e.g. the one above requires 2A on the +5V line, maybe also some on other lines - I am not sure how much the A4000T motherboard uses on its own)

I know that I will also need possibly a 24pin to 20pin ATX adapter, and then a ATX-to-AT adapter, and also an ATX power switch.

Would appreciate if anyone can offer their real experience here.
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Old 15 September 2007, 17:27   #2
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@Clagor

Intersting pickle

Pin 18 (WHITE) should be -5,

I am yet to find one in my house that doesn`t have one of these. (just checked my 650 Enermax... that has it too )

hmmmmies.....

you dont need to worry about a pullup circuit on the plus 5, as you can just connect the PS_ON (green pin 14) to any COM and the PSU will power up.

Theres hardly any voltage so its perfectly safe (well from what i have tested, I had a power amiga running for ages as well as a modded atx to at for an old dosbox for like ever! not a problem not to mention other various projects....)

I would suggest you tie off the correct voltages and use a regular power on/off switch job done
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Old 15 September 2007, 17:45   #3
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@Zetr0

Quote:
I am yet to find one in my house that doesn`t have one of these. (just checked my 650 Enermax... that has it too )
Just checked their website, and only their older ATX v1.3 say they supply it, the v2.0 and 2.2 don't. Maybe if you can point me to your power supply online.

Quote:
you dont need to worry about a pullup circuit on the plus 5, as you can just connect the PS_ON (green pin 14) to any COM and the PSU will power up.
If I don't use an extra power switch, isn't it just a case of using an ATX2AT adapter, and the power switch directly on the PSU will turn on the computer?

Quote:
I would suggest you tie off the correct voltages and use a regular power on/off switch job done
What do you mean by "tie off" the voltages? And what is the regular power on/off switch? Sorry, have not done this before.
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Old 15 September 2007, 19:42   #4
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@Calgor

sorry my friend, I assume too much (thats my fault ) okay... gimmia smidge and i will make a schematic to help
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Old 15 September 2007, 20:26   #5
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while looking for some schematics for the a4000 psu i found this, wich is familiar to your earlier problems

http://wonkity.com/~wblock/a4000hard/-5vprob.html

i found that here

http://wonkity.com/~wblock/a4000hard/comprob.html
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Old 15 September 2007, 20:42   #6
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@Zetr0

Thanks, but the problem with my A4000T detailed in my other thread is not related to the -5V but the user+5v (well, I haven't measured the -5v so who knows....). The current original power supply says on its sticker it supplies it. That thread also has a link to A4000T schematics if that was what you were after.
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Old 28 September 2007, 16:51   #7
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Now I have my ATX power supply, the one linked to at the start of this thread, but I need to know how to hook it up to the power switch on the front of the A4000T.

With the ATX to AT adapter, there are 2 wires coming out from it which are green and black, which are the PS_ON and COM/Ground wires respectively. I know that I need to connect the 2 wires together to start the PSU (as well as having a 2A load on +5V).

But how do I connect the power switch on the front of the A4000T with these green and black wires?

Currently the power switch is connected via live wires directly to the existing AT(LPX) power supply (according to that standard). There are a blue, white and brown wire going from the power supply to the switch, and a thick green wire going from the power supply to somewhere in front of the switch where I can't see.

Here is a link to the AT power supply standard for reference which it is almost like, but not quite (has green wire going somewhere instead of the black):
http://www.pcguide.com/ref/power/sup/partsSwitch-c.html

Last edited by Calgor; 28 September 2007 at 16:56.
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Old 28 September 2007, 17:06   #8
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@Calgor

theres very little voltage on the (green) PS_ON#, you can use an AT On/Off button and just connect the black and green wires respectively...

if you are confident to try, (just to see if you do need a 2a pull up) can you plug the atx psu into the mains, and then just connect the ps_on and black (ground)... the psu should come to life (fans etc) if not then you will require a 1 - 2 Amp pull up (although i doubt)

see how you get on.
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Old 28 September 2007, 17:26   #9
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@Zetr0

I asked the power supply company if it would damage the PSU not to have the 2A load, and they just said without it it would not regulate the voltages properly (i.e. not answering my question - I already knew that). I have 2 x 1A load resistors anyway just in case which I will connect to the drive connectors. Not sure how much load the A4000T motherboard draws.

Regarding the switch, I have seen those with only 2 connectors on the net to which I would connect the green and black wire spade connectors, but the one currently in the A4000T seems to have more than 4, so I am not sure if I need to get myself a new switch? Or if it needs to be momentary or latch (permanent connection) type? Do not know which type the current one is except to guess it is permanent.

BTW, there is actually a black wire I didn't see under the others currently going to the switch, so it conforms to AT standard exactly with 4 wires to the switch, though I have no idea where the green wire is going to or what it is doing.
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Old 28 September 2007, 17:31   #10
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while PS_ON is grounded the PSU (will/should) power up.... just tie the green to the black and your psu will power on....

the load regualtion wont mean that much to be honest, I thought you ment it differently as some server PSU's wont power up UNLESS theres so much draw on specific line (and no i am not picking on compaq for that ...)

all you need to do is connect the green to the black with a switch and it will power no probs m8...

if you want i can attempt to take some pic's for you ...
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Old 28 September 2007, 17:45   #11
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But does the green and black need to always remain connected once the power supply is powered up? And when they are disconnected does that mean the power supply will switch off? (hence why I was asking what type of switch I need).
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Old 28 September 2007, 17:47   #12
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I did not read the whole thread, pick a good quality atx psu, not all deliver correct +5v , even if they are 350W...
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Old 28 September 2007, 19:44   #13
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Quote:
Originally Posted by Calgor
I asked the power supply company if it would damage the PSU not to have the 2A load, and they just said without it it would not regulate the voltages properly (i.e. not answering my question - I already knew that). I have 2 x 1A load resistors anyway just in case which I will connect to the drive connectors. Not sure how much load the A4000T motherboard draws.
If you want to test drive the psu, just connect a hard drive to it while testing.

No reason to make a big issue out of that.. Usually the PSU won't even start if there is insufficient current draw, but nothing will break if so, it will just stay off.

Quote:
Originally Posted by Calgor View Post
But does the green and black need to always remain connected once the power supply is powered up? And when they are disconnected does that mean the power supply will switch off? (hence why I was asking what type of switch I need).
The psu turns off when the connection is broken. You need a switch that stays on.
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Old 29 September 2007, 04:36   #14
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Quote:
Originally Posted by Jope View Post
If you want to test drive the psu, just connect a hard drive to it while testing.

No reason to make a big issue out of that.. Usually the PSU won't even start if there is insufficient current draw, but nothing will break if so, it will just stay off.


The psu turns off when the connection is broken. You need a switch that stays on.
I have seen numerous reports of ppl with cheap PSUs blowing them up if left on for a little while with no load. The better ones (like you must have been using) have some kind of auto shut off. Mine should be fine, but the company didn't answer my question on this, so better safe than sorry.

About the switch always staying on, or being a latch type, that makes sense. Looks like I need a SPST type switch (I think I can also use the SPDT/DPST/DPDT switches as an SPST - see wiki for these). I think the reason in many places it says the ATX switch should be "temporary on" is because it must be connected to the ATX motherboard which uses its own logic to connect/disconnect the connections at the motherboard power connector (including the 4 second power off). Which is very different to using an ATX to AT adapter! Could you please confirm my reasoning is correct?
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Old 29 September 2007, 14:41   #15
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Quote:
Originally Posted by Calgor View Post
I have seen numerous reports of ppl with cheap PSUs blowing them up if left on for a little while with no load. The better ones (like you must have been using) have some kind of auto shut off. Mine should be fine, but the company didn't answer my question on this, so better safe than sorry.
Well yes, I haven't left them on for very long if they don't start.

But why would you leave it on if you see it didn't turn on? Maybe we shouldn't give too much more thought to this issue. :-)

Quote:
I think the reason in many places it says the ATX switch should be "temporary on" is because it must be connected to the ATX motherboard which uses its own logic to connect/disconnect the connections at the motherboard power connector (including the 4 second power off). Which is very different to using an ATX to AT adapter! Could you please confirm my reasoning is correct?
Your reasoning is correct. If the ATX -> AT adapter does not have any logic in it, you will need a switch that stays on.
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Old 29 September 2007, 17:57   #16
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@ Jope

Thanks for confirming. Excellent! Now I know what kind of switch I need - I think I might be able to use the existing AT one as I think it is a DPDT. I think I can put the ATX green and black wires in the position of either the old AT live wires black and brown (which connected the AT "hot" wire) or white and blue (which connected the AT "neutral" wire). Can you also confirm I am not talking crap here??? If the switch type is wrong, there won't be anything damaged. Thanks for all the help!!

And there is still the matter of that green wire from the old AT power supply, what is it doing? (only an A4000T owner will probably know this)

EDIT: Actually, the green wire may be the optional 5th wire in AT spec which should be ground. No wonder it seems to go nowhere except into the case... will need to confirm this.
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Old 29 September 2007, 18:19   #17
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You can use either side of the AT power switch. It's just a switch after all. :-)

And since the green and black are supposed to be connected in the ATX power supply to turn it on, you can't really break anything by connecting them or not connecting them.. You're pretty safe.
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Old 06 October 2018, 14:52   #18
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Sorry for digging out an old thread, i am looking for A4000T PSU pinouts
gonna build a P8/P9 adapter and need a pinout urgently..
Thanks,

Viktor
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