Using a picoPSU: tired of the problems. Please help.

[Amiga1992]

Hello guys,

I've had two picoPSUs for as much as 3 years and try as I might I never got them to work with my blimmin' Amigas. Some people may remember my old thread where I bitched about this and thought I done the mod wrong to one of them and believed it burnt. Well it wasn't.

Now I decided to give it a new try. I have probed all the conenctions with a tester. Everything has been wired properly. So as to not fuck up the motherboard again (or at least not think I did), I wired an ATX connector to an amiga PSU lead. I followed guides here, the Amiga PSU pinout and the ATX pinout.

I tested again that every connection was done right and it was. No shorting, and each pin was properly connected to its ATX counterpart. The connected pins were +5VDC, +12VDC, -12VDC and Ground. Shield was left alone. I connected a switch to the green cable (P_ON) and to Ground.

I connect this cable/adapter thing to the picoPSU and the picoPSU to the mains. I flip the switch and the red light comes up. Great.

Now, I connect the cable to the Amiga. I flip the switch, and NOTHING. The picoPSU turns no red light on. It refuses to power up. Works fine if I unplug it.

On another test, I power it up while unplugged and then i connect the Amiga to it. The Amiga seems to boot (I see the hard drive lights booting as usual), but there is NO video.

Now, what on fucking earth is going on? I am ultra pissed off at this. I haven't had an Amiga power supply for months and I need this to work so I can finally get to work on some stuff I have to do with them. I am SURE I have made no mistake, if there is any omission to what I have done, it is only because te guides that I followed ommited them.

I read about POWER SENSE, does this need to be dealt with? If so, how? But if it is, why does it power up on its own when it is not connected? And why does the Amiga give no video output if I connect the power supply after I turned it on?

Any light shed on this will be VERY helpful because I been pulling my hair with this for YEARS now.

[_psy]

try without the switch to the green cable (P_ON) and to Ground (just connect the cables) and see if thats the problem (i have a power socket switch to power the brick and amiga)

i don't remember now and i can't open the amiga cause i have this monitor on top and stuff! but i think i connected 2 output wires 5v+ from picopsu together and then to amiga connector so it can draw more current (i'm not sure if this helps) and my picopsu 120w has 2 lights 1 green and 1 red which light up.

and check with a multimeter, are all voltages there?

[thgill]

Are you 100% sure your a1200 motherboard is ok?

[Amiga1992]

I tried with two computers, one A600 and one A1200. Both are 100% OK. It is not a problem of the computer.
Why would not having a switch make a difference? It switches on when it is not connected to the Amiga, but it does not when it is.

By the way: I also have TWO picoPSUs. They both act the same way. They are not faulty.
I DID check with a multimeter both for shorts and for power. The readings are normal. I checked more than once.

There are many users of picoPSUs here. I hope someone can help because I am going crazy over here.

[Stedy]

@Akira

Have you wired all the +5V wires together?

I suspect the PSU is not sensing the load as you do not have the +5V sense connection (which can be any +5V output). Luckily for you it has most likely stopped powering it's output. Some PSUs go over voltage. The schematic of my ATX power adaptor is here:
http://www.ianstedman.co.uk/Amiga/de...x_adaptor.html

Just realised I have not published the schematic of the picoPSU variant but the power connections are identical.

Ian

[Amiga1992]

Almighty Stedy i for the help! Thanks man

No, I have not wired those together. I will try doing so. The instructions I have been following never said such things.
What do I do with the 3.3V lines? And why does the picoPSU power up when the Amiga is not connected?

Thanks!

[edit] I am tired of this garbage and I need my machines working ASAP. I ordered two of your adapters. I hope they arrive soon. Merry Christmas to me! :P

[voyager]

There is a topic on a dutch forum about using ATX PSU’s as a lab or experimental power supply.

Because it’s a switching power supply there must me some load on them go get a stable output or ells they start to oscillate. We are using 12+ 12- 5+ but do noting with 3,3. I think if you put some load on the 3,3 line the pico psu will turn on.

From the developer/specs/ATX_ATX12V_PS_1_1.pdf:
No-load operation

No damage or hazardous condition should occur with all the DC output connectors disconnected from the load. The power supply may latch into a shutdown state.

I also use a ATX PSU to power my A1200 but I always wonder if it is a good thing that the 3,3 has no load on it. The forum topic suggests putting some big resistors on the lines you are not using and draw about 1 amp on those lines, but he is only talking about the positive lines. There is also a -5v that

http://translate.google.nl/translate...s%2F885613%2F0

A bad google translate link of the forum topic.

[thgill]

I replaced the internal psu in an Atari STe with a pico psu and didn't need to do anything special to make it work. It only needed the +5 and +12v. Didn't need to worry about the 3.3v at all. I believe they only require a load on the +5v to power up.


@Akira - can you perhaps share with us some pictures of the pico psu and wiring harness you are using?

Also, did you use your meter to verify that the appropriate pins on the end of the amiga psu cable was receiving the correct voltages when the pico psu was powered up? Not just buzz for continuity from point A to point B, but actually verify the correct voltages?


Because if the correct voltages are on the right pins at the Amiga PSU cable end, I can't think of any good reason why this wouldn't work or why the pico psu light would turn off.



Personally, for testing purposes I would use a single +5v wire from the ATX harness as well as +12 and -12v. Also, watch out for one marked as +5vsb - you don't want to use that one. Its always on even when the psu is powered off (unless switched at the mains).


Get us some pics and perhaps we can sort this out for you.

[_psy]

i think if you just do what Stedy and i said above it would work , i used ATX 20 pin Power Extension Cable - 30cm ATX 1.3 for modding cables , but if you buyed Stedy adapters that's a lot more clean solution, good luck man

[Amiga1992]

First off I want to say thanks for all the input. Each time I come back here I restate my belief that this is the best Amiga forum

Originally Posted by thgill

@Akira - can you perhaps share with us some pictures of the pico psu and wiring harness you are using?

OK I will do this tomorrow.

Also, did you use your meter to verify that the appropriate pins on the end of the amiga psu cable was receiving the correct voltages when the pico psu was powered up? Not just buzz for continuity from point A to point B, but actually verify the correct voltages?

I think I mentioned it above. I did and all correct voltages are being output.

if the correct voltages are on the right pins at the Amiga PSU cable end, I can't think of any good reason why this wouldn't work or why the pico psu light would turn off.

The green light is always on. The red light does NOT lit up when the Amiga is connected and I flick the switch to ON.

As I said I have less and less patience for this sort of thing every day so I bought two adaptors from Stedy which I hope would arrive soon. I still would love to understand what is wrong. What power line does composite video output work with? Because as I said it seems that isn't working.

[thgill]

The Green LED on a picopsu means its receiving the 12v power from the little brick, so thats good. The Red LED indicates whether or not the Pico is outputting anything. So with it going off thats obviously no good. My guess is something is shorting it out (possible wiring issue) or perhaps forcing it into overload protection (like if one of the rails is drawing way too much current).

There is just about nothing you could really stuff into an A1200 desktop case that should be capable of drawing more current than even the smallest pico psu is capable of supplying. Unless you have managed not only a PPC board, but also a Mediator busboard and all its slots filled.

I believe you need both 5 and 12V to get it to power up. -12v just powers the audio circuitry and I believe some components in the serial port circuitry, so no need for it for basic power up testing.

Hmmm....I should pick up another picopsu to test in my A1200. Wouldn't mind just having the small brick on the desk.


With all these PSU troubles you have been having, if you lived here in the States I would just send you my back up modded ATX psu for free.



Edit:
Just had another thought.

I know I mentioned this before, but make sure you are NOT using the +5vsb connection on the ATX connector. Besides the fact its always on regardless if the switch is turned on or off (so long as the brick is still plugged in) it also has far, far less current ability. For example the 120W pico can only supply about 1.5 amps on the +5vsb rail. That is just too low a current for the 5v and would barely be able to power up a bare 1200 with no accelerator and no hard drive. And I would imagine the smaller 90 and 80 watt pico would be even less.


So, make damn sure you are using one of the regular +5v rails on the psu and NOT the +5vsb.

[Amiga1992]

Well it isul upsetting. I had this problem before with different wiring roo.

I tested TWO picoPSUs amd TWO different working Amigas (one a600 and one a1200).
I have to emphasize on this though: the light does NOT turn off. It just simply doesnt turn on when plugged to the Amiga. If I turn it on and then connect it to the Amiga, it remaIns on, but i get no video signal comIng frOm the Amiga.

I want to see what happns when i get the adapters. I cant possibly have two malfunctioning picopsus, that would be the worst luck ever :/

Cheers

[thgill]

Again, are you using the +5vsb connection on the atx connector or one of the regular +5v rails? This is important as what you are describing sounds a lot like the +5vsb is being used. On an ATX pinout diagram its marked usually in purple and sometimes called 5v standby.

[Amiga1992]

I am using +5V, not +5SB.
Here is the connector:



No laughing allowed
The thinner wires is what I added joining all the +5V lines (including +5VSB, should I remove that?).

[thgill]

Yes.

DON'T use the +5vsb. Clip the wire going to +5vsb. Never wire both a regular 5v rail and +5vsb on an ATX power supply together like that. Most likely as soon as a load is present (plugged into the 1200), you are sending the pico into protection mode.

[Amiga1992]

OK, let me see what happens like that.

[roy bates]

dont connect the +5vsb ,its for a constant 5 volts at about 2 amps max for the circuit that turns on the psu from a push button on cases.(it powers a flip flop circuit on pc motherboards)


on the motherboards this wire and the ground and ps-on are used to switch the psu on and off(in conjuntion with a push button)

[Amiga1992]

Hooly smokes, the adapters are here! That was VERY fast Ian, thanks a lot!
Now the moment of truth, plugging them up. Will report later. But I will give my own adapter a try after I am done with this.

[Amiga1992]

I am totally angry man.

I tried Ian's adapter.

SAME RESULTS. Green LED on. RED turns on whe nI flick the switch as long as the picoPSU is disconnected. Plug Amiga PSU cable to Amiga. Flick the switch. NO RED LED coming up.
How can this be? How can two different PSUs do the same?

I was wondering: could it be the AC Adaptor?????

[thgill]

Could be.

Which model Picopsu and which AC adapter are you using?

The ac adapter most of the pico's ships with is a 12v 60 watt or greater unit.