Amiga power supply project

[britlord]

Hi Guys. Here's my new Amiga power supply project. I'm gonna fit a baby AT PS into a spare Amiga power supply case that I bought off eBay. The reason that I picked AT PS over ATX one is that there's not many wires to remove from the board (I don't like leaving cut wires left in the board), so far I have removed the PCB and removed all the wires. But I kept the 110/220v switch wired to the board, cos that's going into the case too.. I have bought a lighted power switch and I will used the plugin power socket too.

The power supply is rated at 150 Watts, so it'll provide plenty of power to my A1200. Lucky for me the PS was never used, and I did a test fit. Perfect fit. I will even be able fit screw down the top case... Oh I found out that the Orange wire (Good) has to go to one of the +5v holes for the PS to work (Not sure why though). Please enlighten me about that (If anyone knows)..

Mike...

 

[roy_bates]

the mains input voltage selector can be got rid of,as its just on or off.

 

[jcarvalho]

That is strange (the orange wire!) I have an normal AT PSU 200Watts and dont need the orange wire... I hope that 150W would be enought... My 1200 has some difficulties to boot properly with 200W PSU. The only thing is that the 1200 has an apollo 1260..

 

[Mr B]

Oh I found out that the Orange wire (Good) has to go to one of the +5v holes for the PS to work (Not sure why though). Please enlighten me about that (If anyone knows)..

The orange cable is "power good" and needs to be hooked to either 5v, or ground... I thought it was ground, but your experience indicates the opposite. Don't have any AT PSU's around anymore, so i cant test it. Either way, when the voltages stabilize, there should be a 5v reading over that pin, or it wont "power on".

The same goes for the gray wire in a ATX PSU, that has to be hooked to a black wire for ground, to power it up. Actually, that's not quite true. Grey applies +5v and if the PC doesn't see it, it wont let the CPU power up. Some ATX PSU's will for what ever reason not fire up if this isn't connected to ground. In that case i'd suggest bundling it with the green cable. Green to ground can be used as a power switch. Grounded green = on, no ground = off.

An AT PSU should be loaded with at least 0.5A on all lines to make sure it maintains stable voltages. Seeing as all AT PSU's around today would be quite old, i actually have to say i'm sort of skeptical towards it's use as an Amiga PSU. I'd much rather go with something more purpose built, or a new, cheap, quality brand ATX PSU. But since you already got the AT, run with it, and see how it turns out. Good luck.
B!

 

[roy_bates]

an AT supply will power on without the orange wire connected to anything.

 

[britlord]

Oh I found out that the Orange wire (Good) has to go to one of the +5v holes for the PS to work (Not sure why though). Please enlighten me about that (If anyone knows)..

The orange cable is "power good" and needs to be hooked to either 5v, or ground... I thought it was ground, but your experience indicates the opposite. Don't have any AT PSU's around anymore, so i cant test it. Either way, when the voltages stabilize, there should be a 5v reading over that pin, or it wont "power on".

The same goes for the gray wire in a ATX PSU, that has to be hooked to a black wire for ground, to power it up. Actually, that's not quite true. Grey applies +5v and if the PC doesn't see it, it wont let the CPU power up. Some ATX PSU's will for what ever reason not fire up if this isn't connected to ground. In that case i'd suggest bundling it with the green cable. Green to ground can be used as a power switch. Grounded green = on, no ground = off.

An AT PSU should be loaded with at least 0.5A on all lines to make sure it maintains stable voltages. Seeing as all AT PSU's around today would be quite old, i actually have to say i'm sort of skeptical towards it's use as an Amiga PSU. I'd much rather go with something more purpose built, or a new, cheap, quality brand ATX PSU. But since you already got the AT, run with it, and see how it turns out. Good luck.
B!

Well I'm no electronic expert LOL (I just dabble in it). But this is where I got the info on hooking up a AT PS to a Amiga, and connecting the orange wire (Power good) to the +5v line (Which I've done), and it says that I also have to connect a 21W car bulb across the +5V (RED) and 0V (BLACK) wires. This will provide a suitable load to turn on the PSU, is that true, if so I'll use a power resister instead, or is the Amiga a suitable load to turn it on instead of a bulb...

http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_Power_supplies/body_amiga_power_supplies.html

Mike..

 

[roy_bates]

the 21 watt light bulb is for testing under load when the amiga is not connected.

as far as i know,the amiga is enough load for the AT supply mate.

 

[britlord]

the 21 watt light bulb is for testing under load when the amiga is not connected.

as far as i know,the amiga is enough load for the AT supply mate.

Phew thanks for that news..

Mike..

 

[Bryce]

The grey "Power good" wire is an output! Definitely don't connect it to either 5V or GND otherwise you'll probably damage the PSU. When the PSU has stabilised the voltages this wire goes from 0V to 5V output to let the computer know it's ready to go. You can use it to power and LED or something if you like (in series with a 470Ohm resistor).

Bryce.

 

[britlord]

The grey "Power good" wire is an output! Definitely don't connect it to either 5V or GND otherwise you'll probably damage the PSU. When the PSU has stabilised the voltages this wire goes from 0V to 5V output to let the computer know it's ready to go. You can use it to power and LED or something if you like (in series with a 470Ohm resistor).

Bryce.

Oh. Are you sure that you right, cos the Website say's that if it's a AT PSU then connect the Power good wire to the +5v (Orange on my AT PS). If it's a ATX PSU then Power good goes to the ground, as for a LED. There is a connection on the AT board for it...

http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_Power_supplies/body_amiga_power_supplies.html

Also I notice that on the old Amiga PSU, the Live wire (Brown) first goes to a fuse. But on My AT PSU(That I'm gonna use) it's the neutral wire (Blue) that goes to the fuse. Does it matter what wire the fuse is on..

Mike..

 

[rkauer]

No difference, but always prefer to put the fuse in the live wire.

And never, ever, ditch the mains ground connection.

 

[britlord]

No difference, but always prefer to put the fuse in the live wire.

And never, ever, ditch the mains ground connection.

Ok, as my case arrive, so now I can finnish this AT Amiga PSU but wish me luck that it don't blow up. Oh as for the power good wire. Should I leave it connected to the +5v or just removed it..

Mike..

 

[rkauer]

My advice is to keep is floating. You can build a circuit to monitor the signal and shut off the PSU if it goes to 0.

http://en.wikipedia.org/wiki/Power_Good_Signal

 

[britlord]

My advice is to keep is floating. You can build a circuit to monitor the signal and shut off the PSU if it goes to 0.

http://en.wikipedia.org/wiki/Power_Good_Signal

Yep I read that, so I'll leave the wire connected to the +5v Oh what's floating..

Mike..

 

[rkauer]

Floating = not connected.

 

[britlord]

Floating = not connected.

Ok. Anyway. I've soldered the Amiga cable to the AT PSU. Amiga Colour is Brown : +12v, Red : +5v, White: -12v, Black: ground. All is left is the yellow wire : Shield. Can I just solder it to ground (where the black wire is) or should I just leave it "floating" (Heat shrink over it, cos there's a pin on it). These questions might sound stupid, but I only have just one Amiga (A1200) and don't want to blow it up..

Mike..

 

[rkauer]

Whatever you like, I personally connect shield wires to the carcass (metal body) of the power supply or a true earth wire.

 

[britlord]

Whatever you like, I personally connect shield wires to the carcass (metal body) of the power supply or a true earth wire.

Ok, done. Anyway, I've finnished the AT Amiga PSU project, and I've doubled checked all the wiring and all's a-ok. However I never did turn on the PSU (When I bought it) cos I don't have any old AT motherboards around, so fingers crossed, that when I turn it on. It doesn't blow the Amiga mobo up.. Oh as for not having the fan fitted. I don't think the PSU will get hot enought just powering my humble A1200, so not needed, Unless I'm wrong..

Mike..

 

[britlord]

Update guys. My Amiga AT PSU (That's what I call it) is working. Just switched it on (With the A1200 connected) and Both power LED'S came on and I put a WB disk in Phew!!! Amiga booted right away, so my AT PSU project works. I even left the AT power good wire connected to a +5v line and no burn up. My PSU is rated at 150 watts (Way more than the Amiga one). Which is Plenty for my A1200. Now I'm just waiting for a MC68882FN40A chip and the rest of the parts to arrive, so I can install the 8meg Hawk board, get my Amiga all hooked up on my desk...

Mike....