ATX PSU stops after secs spinning

[roy bates]

i have got atx supplies that work without load,funny that.

and i have some that dont,but do work with a flip flop as a on off switch.(all work with a flip flop which is basicly steadys adaptor)

[Loedown]

Originally Posted by roy bates

i have got atx supplies that work without load,funny that.

and i have some that dont,but do work with a flip flop as a on off switch.(all work with a flip flop which is basicly steadys adaptor)

Sarcasm is the lowest form, factor that into the loose design standards of the ATX supplies and there's your problem right there. Even you admit you have some that don't work without a load so I offered a solution to a problem, something that I discovered first hand when I needed a load to start a PSU that was running 4 fans for a friend of mine around 1992 or so.

[roy bates]

Originally Posted by Loedown

Sarcasm is the lowest form, factor that into the loose design standards of the ATX supplies and there's your problem right there. Even you admit you have some that don't work without a load so I offered a solution to a problem, something that I discovered first hand when I needed a load to start a PSU that was running 4 fans for a friend of mine around 1992 or so.

there was no sarcasm in my post(if that was what you was trying to say),even the post about softstart supplies.
i was just simply saying some do, some dont.

@retrofan,sorry forgot to mention the vsb +5 volts line is to drive the flip flop circuit on the motherboard for switching the supply on.(this is on constantly for obvios reasons)

when the button this circuit is wired to is pressed the circuit gets pulled low on the ps-on wire thus starting the supply.

[FOL]

Originally Posted by roy bates

there was no sarcasm in my post(if that was what you was trying to say),even the post about softstart supplies.
i was just simply saying some do, some dont.

@retrofan,sorry forgot to mention the vsb +5 volts line is to drive the flip flop circuit on the motherboard for switching the supply on.(this is on constantly for obvios reasons)

when the button this circuit is wired to is pressed the circuit gets pulled low on the ps-on wire thus starting the supply.

I think this thread has been informative. As I have learnt something about wierd operations of newer psu's. Personally for me, a psu that does'nt work without load is just wrong.

@loedown,
I dont think roy ment his post as being sarcastic. The use of "funny that" could be taken as sarcastic, but I saw it as "its very odd". Its annoying how some things can look like they are not.

[Retrofan]

Originally Posted by roy bates

and i have some that dont,but do work with a flip flop as a on off switch.(all work with a flip flop which is basicly steadys adaptor)

So that's the answer to my question about why Ian's adapter doesn't need a big resistance. I would appreciate an Ebay link for a two pins? flip flop switch, I would like to try it.

[Loedown]

@FOL / All

The trouble with ATX supplies is that they're all built to a budget and that means that standards go out the window, they will all run the same way but the way that they achieve the supply is what makes them all different and that's why some will work with the old green to black trick and others need a minimum load to start and others further still need Stedy's flip flop solution.

@Retrofan

Ian has the circuit for his flip flop on his site you could just follow that on a simple prototype board.

http://stores.ebay.com.au/Thai-Shop-Etc

This guy sells some great stuff and free postage, I can say the quality is very good too and very friendly.

@Roy Bates

Funny That, yes I interpreted that as being sarcastic, if it wasn't meant that way so be it.

[Retrofan]

Originally Posted by Loedown

@Retrofan

Ian has the circuit for his flip flop on his site you could just follow that on a simple prototype board.

http://stores.ebay.com.au/Thai-Shop-Etc

This guy sells some great stuff and free postage, I can say the quality is very good too and very friendly..

I agree that ian's adapter is great. The only problem with it is that you have to retain all the cables with the 20pin connector, so if you are making something internal it looks very ugly.

I have to look that schematics still, but I think that it would be a great thing if he would sell just that part of his ATX adapter, so everybody could cut the wires and make it cleaner.

[Loedown]

Originally Posted by Retrofan

I agree that ian's adapter is great. The only problem with it is that you have to retain all the cables with the 20pin connector, so if you are making something internal it looks very ugly.

I have to look that schematics still, but I think that it would be a great thing if he would sell just that part of his ATX adapter, so everybody could cut the wires and make it cleaner.

With the extra room afforded in an ATX case why not mount Ian's mod inside it with LOTS of insulation in case of it coming loose and shorting out on something high voltage and mounting a simple push button switch on the outside of the ATX case?

[Toni Wilen]

I think I have said this previously but I'll repeat: Cheap ATX supplies are complete crap, they usually don't even handle half of their advertised wattage and have ultra-crap regulation and lots of ripple. Some of them are dangerous to use:
http://www.jonnyguru.com/modules.php...=Story&reid=71

(OP:s powersupply seems suspicious, it is ancient design because it has much more current on +5v rail than on +12v rail. It is not "new". No name. Too cheap.)

More expensive and independently regulated versions should work fine even if +12v is not loaded at all. (every line has own regulation)

[roy bates]

the part steady used for the prototype board was a 74LS74 and a momentary action push to make switch.and a few resistors etc .

you can make it very cheaply and very small on proto board and put it insde the power supply.(bolted to the top sheild)

http://www.ianstedman.co.uk/Amiga/am..._supplies.html

the parts are extremely easy and cheap to get.

heres the flip flop.

http://www.ebay.co.uk/itm/SN74LS74N-...item3a6e7d5524

switch(it doesent have to be exactly like this one its just an example)

http://www.ebay.co.uk/itm/Quality-Mo...item2a147b03f1


pcb(just cut it to size after you build it and make it so it can be bolted on)

http://www.ebay.co.uk/itm/64-x-95-mm...item460d2be923

as you can see,it can be made very cheaply you could probably make it fit on a board around 25mm x 50mm or less including bolt holes

just scroll down a bit,the circuit is there you can print it off and read it at leasure.and yes it is a good idea to have a load on the supply so it regulates properly.


@loedown,the problem with the english language is that any word has 3 or more meanings.even worse if its just text.

[Retrofan]

Thanks. Instead of buying the components and making the board I think I will use Ian's adapter just connecting to the 20pin female connector the cables for +5vsb, +5, grey, ground and +12

[Hewitson]

Originally Posted by FOL

I think this thread has been informative. As I have learnt something about wierd operations of newer psu's. Personally for me, a psu that does'nt work without load is just wrong.

Many switching power supplies do not operate without a load. This is a protection feature, as running an SMPS without a load will damage it.

[roy bates]

no probs retrofan,good luck with it anyway.

[Retrofan]

Originally Posted by Toni Wilen

I think I have said this previously but I'll repeat: Cheap ATX supplies are complete crap, they usually don't even handle half of their advertised wattage and have ultra-crap regulation and lots of ripple. Some of them are dangerous to use:
http://www.jonnyguru.com/modules.php...=Story&reid=71

(OP:s powersupply seems suspicious, it is ancient design because it has much more current on +5v rail than on +12v rail. It is not "new". No name. Too cheap.)

More expensive and independently regulated versions should work fine even if +12v is not loaded at all. (every line has own regulation)

I think I won't go on any more with this PSU. Reading your link has convinced me, Toni. I bought this to power my more expensive miggy, BPPC/BVision, so I think I will search for something more reliable and not so cheap.

Any advice about a brand with know good ripple is welcome. Edit: http://www.eggxpert.com/forums/thread/323050.aspx

[Hewitson]

I have been using the Antec power supplies for a few years. I could not be happier with them, they are very good quality units.

[Stedy]

Hi,

You will have regulation issues with any ATX PSU if you do not use the 20/24 pin ATX connector. Some PSUs have dedicated wires, others double up, that sense the voltage at the load, in this instance, the PC motherboard. This is to boost up the supply voltages at load.

For example, with 20AWG cable and a 5 amp load, 30cm long, there will be a voltage drop of 150mV, enough to stop a 3.3V powered device go out of spec and 60% or the tolerance of a 5V supply.

My ATX adaptors connect all the +5V and +12V wires into appropriate groups, thus making the feedback loop required by the ATX PSU. Ideally the feedback should be on the Amiga but for the 2-4A of wedge Amigas, it's not too bad.

If someone wants a customised adaptor, within reason I may be able to accommodate you. I have cable connectors for the ATX plug and a few Amiga type connectors shortly.

The ATX adaptors I sell are tested by plugging into an ATX power supply and toggling the power switch. I use no load and the outputs are stable. Have not seen a switchmode converter in the last 15 years that was unstable with no load.
During the validation of the design, I used my A1200/040 with drives and monitored the power supply voltages and also used car bulbs as resistive loads.

As Toni stated, some cheap ATX power supplies are crap. I had some @ work, they could not handle the surge currents of my 48W processor card easily (4-7A @ 5V) and 2A @ 3.3V, the same supply failed EMC testing, even though it was CE marked!

Hope this explains a few peculiarities of the ATX power supply.

Ian

[roy bates]

some expensive supplys are crap as well,i had one that cost me £56 and lasted a whole 5 days,i think you can get crap supplys if there cheap or expensive.(just bad luck in my case)
yes, it was new.

[Jope]

Originally Posted by Stedy

the same supply failed EMC testing, even though it was CE marked!

I'm sure you know the CE mark doesn't have a certification agency behind it, it's just the manufacturer's declaration that they think the device is safe and does what is advertised. :-)

The Chinese even have a fake CE mark, which stands for "China Export" :-D

[Retrofan]

So what I was thinking:

Originally Posted by Stedy

You will have regulation issues with any ATX PSU if you do not use the 20/24 pin ATX connector. Some PSUs have dedicated wires, others double up, that sense the voltage at the load, in this instance, the PC motherboard. This is to boost up the supply voltages at load.

And this:

Originally Posted by zharn

...Turned out all i had to do was connect the amiga 5v to all the red 5v on the mobo connector and now the power supply will stay on. Used it for a couple of hours no problems.

The proof is that I've tried now to use the cables I've retained connecting them to the 20pin connector and this to Ian's adapter but now it stops after few spinnings. So it seems any cutted wire was sensing the voltage at the load. Edit: I could solder all the 5v wires (& holes at the mobo) together, and surely I will do, but ...

Well, it's good to know that, but anyway I will be buying a better PSU.