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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: badgerme on July 30, 2008, 04:46:15 PM
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How do - I've got an AT power supply rated at 200W with an AT to Amiga adapter cable to connect the Amiga straight to the power supply. Question is - when the AT PSU was in a PC - there was a cable that connected the case to the mobo that turned the PSU on - how do you turn the PSU on without the motherboard? (Its definately an AT PSU and not an ATX)
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AT? I've modded an ATX PSU for a A1200 before, but AT - I mean, no big mains clunky case power switch?
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afaik, the only way to turn on one of those clunky PC supplies that turns on via motherboard signal is to jump two pins in the motherboard connector. now if only I could remember which ones! :) I remember it being fairly obvious from the psu pinout but ymmv...
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This doesn't sound right. The AT psu usually has a toggle switch in the mains power feed, while an ATX doesn't, and is turned on by the motherboard connecting (psu colours) green to black from the low voltage "momentary" switch on the front of the case.
Are you sure its an AT psu ?
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AT PSUs usually have a mains(!) switch that hangs off a piece of cable. If the cable has been removed and short-circuited, you'll have to undo the mod - or get another PSU.
You can easily tell AT and ATX PSUs apart: the former's connector consists of two parts, one row of contacts each (plus the mentioned cable). An ATX PSU's connector runs two rows of contacts.
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there is a black cable hanging out of the power supply with connectors which connect to the power supply switch. The colours of the wires are black, brown, blue and white. The diagram indicates on the PSU that the all four connect to the same switch.
It also says on the diagram that the L (live im assuming) is switched by connecting the black and brown wires, and the N are switched by connecting the blue and white wires.
It appears that the two sets of wires are connected to each other when the power supply switch is switched on.
Unfortunately I don't have the switch - the PSU didnt come with one :(
Can I simply just connect up the black to the brown wire, and the blue to the white wire permanently for it to turn on or does it need a proper PSU switch?
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Without seeing the psu I don't want to advise in case you connect it incorrectly ! What you say sounds OK, but if you are not sure, please contact a competant technical person :-o
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ditto Homer's post ;-)
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You could just short the wires together but I wouldn't recommend it. It would be better if you find a switch to connect the wires. If they are shorted then the PSU would be running all the time it is plugged in. It can damage itself if it is run without a load.
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I have a AT psu with the same cable and colors, i've conected Black with Brown and White with Blue, the psu now starts automaticaly when you plug it on (this was from the sticker on the psu, i don't have the switch that came with the case), the psu works fine.
Recomend to use a multimeter to check the voltages and corrents on +12v , +5v and -12v to see iff they are in range to use it safe with an amiga (See Picture). (some low voltages on -12v may damge sound circuit, and other issues).
(http://vlrqyg.blu.livefilestore.com/y1pfv0aXK1itbCPZMEeLn0183uGPPgKBUfqppmSrzwGx7aArkm_l7MRfN9-TH2skntlviRnBGCQHGU/Voltages.jpg)
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In all AT PSU I've converted to Amiga use I do the same:
Link blue and white wires directly on the PSU's board and route the remaining two (black and brown) to the switch of the original Amiga brick.
If the AT PSU you are using is the "baby" format, it's dead easy to toss it inside the original A500-sized brick. No need for the fan.
If is the larger AT PSU, then take the Amiga brick's switch and use it to power-on your power supply unit.
Final result here:
(http://www.rabayjr.com/Amiga/Fonte_Amiga_1_resize.jpg)
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You can't beat this site for Amiga/ATX power supply tech info. I used it to help me put an ATX suppy on my A3000.
Amiga Power Supply Guide (http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_Power_supplies/body_amiga_power_supplies.html)
Plaz
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okie dokey - got it working with the switch. Have shorted the blue/white (neutral) wire, and then switched the brown/black cable. Nice AT power supply conversion! Hope you don't mind but I've adopted the layout with the switch - bloody good idea!
Ok - heres the thing, the +5v and +12 rails read well within the +-5% range, yet the -12v rail is 0.1 volts too low - do you think this will matter? This makes it 5.83% in range? What do you reckon guys?
Also on another note - I thought I'd stick a multimeter across my A500 power brick to see what it was reading. Turns out the minus 12v rail (-12v) on that is -18v!!!!! how the hell has my amiga survived all this time? Should I continue using it??
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The low reading on the -12v its probably because you don't have anything conected to the psu on the +5v or +12v (don't remember witch), but try to connect a cdrom or dvdrom on the psu and then check the voltages on the -12v.
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badgerme wrote:
How do - I've got an AT power supply rated at 200W with an AT to Amiga adapter cable to connect the Amiga straight to the power supply. Question is - when the AT PSU was in a PC - there was a cable that connected the case to the mobo that turned the PSU on - how do you turn the PSU on without the motherboard? (Its definately an AT PSU and not an ATX)
If it's a standard AT power supply then by definition it would have to have a phyiscal switch. Be it on a cable in the front bundle or only on the back of the unit itself.
Unless it's a custom AT power supply that somehow added a power on signal like ATX has, I can't think of any other way.
Could someone have just cut off the power switch? If so just add one on the loose wires.