Making a Diy A1200 Power Supply HELP

[Stedy]

Originally Posted by XsamX1987

So basically would this of been more simple if I had just left the Power Supply Just the way it was before I removed nearly all the wires ?

Yep But considerably less educational.

You should read my detailed guide on all this:
http://www.ianstedman.co.uk/Amiga/am...su.html#ATXPSU

The top end power figure for an Amiga with PPC 7400/7410 + PCI motherboard and Zorro cards is around 150W. Clearly any reasonable, low wattage PSU will work. An A1200 with 68060, HDDs and SCSI card needs 16W, http://www.ianstedman.co.uk/Amiga/am...uredamigapower

I'll add the A4000+PPC 7400 power figures to the guide soon.

By the way, what was the power rating printed on the label of your PSU?

Ian

[XsamX1987]

Originally Posted by Stedy

Yep But considerably less educational.

You should read my detailed guide on all this:
http://www.ianstedman.co.uk/Amiga/am...su.html#ATXPSU

The top end power figure for an Amiga with PPC 7400/7410 + PCI motherboard and Zorro cards is around 150W. Clearly any reasonable, low wattage PSU will work. An A1200 with 68060, HDDs and SCSI card needs 16W, http://www.ianstedman.co.uk/Amiga/am...uredamigapower

I'll add the A4000+PPC 7400 power figures to the guide soon.

By the way, what was the power rating printed on the label of your PSU?

Ian

Thanks for the Reply and yes this is more Educational and fun

so your Guide will tell me how to How to fix my problem and what Resistor I need ?


I think this is what you asked for Its a 500w And Orange +3.3v 26A Red +5v 27A yellow +12v 22A Blue -12V 0.5A purple +5VSB 2.0A Black ground Green Ps-on Grey pw-ok

[XsamX1987]

Originally Posted by Daedalus

As said, it's nothing to do with a momentary switch - pulling (and holding) the _PS_ON signal low is the ATX standard method of activating the supply. The momentary action just feeds into the motherboard's power control circuitry that actually does the switching on and off of the PSU.

Also bear in mind that, for many ATX PSUs these days, it's the +12V rail that's the "primary" output and the one which needs to have a minimum load. This is due to modern PCs taking most of their power from 12V instead, in particular modern GPUs. As a general rule (but of course there are exceptions), the highest power output from a PSU like this is typically the main output and the one which needs to be loaded. So check which rail outputs the most watts, and then see about loading that. Sometimes a couple of old hard drives might be enough, but the best bet is a resistor.

A decent ATX power supply will shut itself down to protect the computer when it can't stabilise its output within spec. This could be because of the sense wire being disconnected as Stedy suggested, or simply not enough load. This is probably better than a lesser PSU that doesn't have the safety feature built in, which could happily supply too high a voltage to your Amiga.

Hey thanks for the Reply, Which wire is the sense wire and il go for the resistor, which one do I go for ?

[elenachen]

Originally Posted by XsamX1987

Hey thanks for the Reply, Which wire is the sense wire and il go for the resistor, which one do I go for ?

That depends on the PSU you are using.

[XsamX1987]

Originally Posted by elenachen

That depends on the PSU you are using.

Here is a picture of the Label

https://postimg.cc/image/syvh2gmd3/


Or 500w And Orange +3.3v 26A Red +5v 27A yellow +12v 22A Blue -12V 0.5A purple +5VSB 2.0A Black ground Green Ps-on Grey pw-ok

[elenachen]

Originally Posted by XsamX1987

Here is a picture of the Label

https://postimg.cc/image/syvh2gmd3/


Or 500w And Orange +3.3v 26A Red +5v 27A yellow +12v 22A Blue -12V 0.5A purple +5VSB 2.0A Black ground Green Ps-on Grey pw-ok

What I meant is that you need a schematic or reverse engineering of the PSU, because each one is different.

[Daedalus]

Sometimes - but not always - the datasheet or technical specs on the PSU manufacturer's website will list the minimum current required on each rail. That's what you need to be able to determine the correct resistor.

As for the sense wire, it will be a much thinner wire that goes to one of the terminals in the ATX connector along with a thicker wire, usually the same colour. So if it's on the 12V rail, look for two yellow wires going into one terminal, one much thinner than the other. That will be the sense wire, and there can be more than one.

[XsamX1987]

Originally Posted by Daedalus

Sometimes - but not always - the datasheet or technical specs on the PSU manufacturer's website will list the minimum current required on each rail. That's what you need to be able to determine the correct resistor.

As for the sense wire, it will be a much thinner wire that goes to one of the terminals in the ATX connector along with a thicker wire, usually the same colour. So if it's on the 12V rail, look for two yellow wires going into one terminal, one much thinner than the other. That will be the sense wire, and there can be more than one.

Thanks for getting back to me

I found the wire, a thinner brown wire with a orange +3.3v 26A on the 24pin connector

I don't know the Make as all it says on the sticker is Atx Switching Power Supply Model ATX-500B

[FOL]

Originally Posted by XsamX1987

Thanks for getting back to me

I found the wire, a thinner brown wire with a orange +3.3v 26A on the 24pin connector

I don't know the Make as all it says on the sticker is Atx Switching Power Supply Model ATX-500B

Last time I did one of these sense power PSU's, I had to connect the sense to the 3.3v rail. Then power supply would run fine.


Your PSU is just a Generic one. Nothing special. You tap in ATX-500B in google it comes straight up.

[XsamX1987]

Originally Posted by FOL

Last time I did one of these sense power PSU's, I had to connect the sense to the 3.3v rail. Then power supply would run fine.


Your PSU is just a Generic one. Nothing special. You tap in ATX-500B in google it comes straight up.

Ok so From looking at The Board and Reading online and from you said, I Connect a wire from 3.3v to 3.3vsr29 For the sense wire

Are you Saying I Probley Don't need a Resistor ?

I know its a cheap PSU But even putting ATX-500B Diagram in to google I still cant find it

[Daedalus]

Yeah, the sense wire needs to be connected to the 3.3V output by the looks of things. Whether you need a resistor after that depends on whether the PSU is stable as it is or not.

[XsamX1987]

Sounds good to me, So Lets say I hook up my Multimeter for a few hours testing the Output to made sure there's no Major Loss or Rise would that be a good idea ?

[XsamX1987]

Originally Posted by Daedalus

Yeah, the sense wire needs to be connected to the 3.3V output by the looks of things. Whether you need a resistor after that depends on whether the PSU is stable as it is or not.

Sorry Forgot to Quote you in the Reply.

[Daedalus]

Hehe, no problem Yeah, just keep an eye on it. Ideally a scope would be better since then you'd see things like spikes and troughs, but in general, if a PSU is going to drift away from its target voltage, it will do it within the first minute. The 5V line is the critical one to measure, and anything more than 0.25V either way (on the motherboard) is probably too much.

[XsamX1987]

Originally Posted by Daedalus

Hehe, no problem Yeah, just keep an eye on it. Ideally a scope would be better since then you'd see things like spikes and troughs, but in general, if a PSU is going to drift away from its target voltage, it will do it within the first minute. The 5V line is the critical one to measure, and anything more than 0.25V either way (on the motherboard) is probably too much.

ok I have Been Running it For a few days now its Perfect thanks for the Help

Here are 2 pictures