A1200: now a PSU issue...

[starf81]

It seemed a reasonable solution so I've tried but it didn't work.

As "dummy charge" I've used some car lights with a value from 5w to 45w. Nothing happens  :-(

I'll look for a better ATX supply or for an old AT...

Thanks for your interest.
Alex

[Framiga]

mhhh, interesting.

Just for the sake of . . . have you checked the +5volt line when the PSU is installed in the PC?

About all the ATX PSUs, has a wire tyed to the mobo (sense), that detect and compensate the 3.3Volts output.

Some others has this compensation line, even on the 5 volt rail. (it compensate the loss of the wires, and "says" to the PSU to raise the voltage if needed).

Pin 11> 3.3volt sense

About the 5volt sense, i think that only some so called "server ATX PSUs" have it.

Anyway, probably your PSU is only tired ;-)

EDIT- thers a guy her on AOrg (sorry don't remember the nick) who is using a "Antec True Precision" bla, bla that sounds interesting.

http://www.silentpcreview.com/Sections+index-req-printpage-artid-61.html

a very impressive test.

[Gringueiro]

I have an old A1200 with a rewired PC supply and I have had similar problems in the past. In my case I discovered that the problem was inside the Amiga. I had wired all my additional internal goodies to the same plug that supplies the floppy drive et al. The problem is that this connector is not very secure and makes bad contact. In addition when the machine draws a big current load (such as at bootup) the small plug just can't deliver, especially if the connection is also dodgy (as in my case). I guess the solution would be to change the plug and put in a heavier duty one, but that would involve a lot of soldering and my motherboard is already tired and covered in my amateur solder jobs, so for now I just wiggle the connector from time to time when I have a problem and it goes back to normal for a while. Your milage may vary ....

[bludger]

I'm running a powershot cable from a 430 watt AT (not ATX) server P/S.
 
This unit has a power switch on the back, neater than having an 18 inch cable draped across the desk.

It runs my 1200 with lots of extras and plenty to spare.

[Stedy]

@starf81

Did you try connecting the car bulbs to the 3.3V supply?

Measure the voltage at the PWR-OK (pin 8, wire colour Grey), it it above 2.0V?

Have you re-wired the Amiga power plug to the ATX PSU?

Try connecting pins 1 to 11 (3.3V to 3.3V sense) and see if it helps.

My 6 year old ATX PSU powers my Amiga fine. I will check a spare (more modern) PSU if I get a chance and see how well that works.

Ian

[starf81]

Hi Stedy!

Yes, I've connected car bulbs to the 3.3V. Obviously they turned very light but it was a good charge for the PSU since I listened to its fan spun up.
However, I've tried to use this charge also on the +5V and +12V channels.

I've not measured pin 8 voltage but I'll do...

Regarding the plug, I've used my original A1200 PSU cable re-wired directly to the ATX supply. So the plug is the Commodore one supplied with the Amiga.

I'll try to connect pins 1 and 11, too.

Regarding the age, I bought this PSU exactly six years ago (it was June '99) while the other one I've tested was been bought more or less 18 months ago.

Thanks for your interest
Alex

[Framiga]

i'm a little confused now:

"Yes, I've connected car bulbs to the 3.3V. Obviously they turned very light but it was a good charge for the PSU since I listened to its fan spun up.
However, I've tried to use this charge also on the +5V and +12V channels."

but . . . have you done this measurements, without any charges (ie with th PSU plugged to your A1200) on the others lines?

Its absolutely uneseful to test a PSU in such way!

To be 100% sure that your PSU (or PSUs in this case) is gone, install it on the PC and test the +5volt line.

If the 5volt is within tollerance and the PC works, could be a problem on your A1200/CPU card that drain too much current (ie a short somewhere or the wires plug)

[adonay]

Had the same problem use the blue (-12)volt cable on the atx socket for ground that solved my problem try messuering b4 connecting tho to be on the safe side

adonay :-D

[starf81]

Absurd!

I've tried to connect the ATX PSU through the 4-pins floppy port adding the -12V to the standard Amiga PSU port (I've read some towers are connected in this way) and... IT WORKS!!!
I really can't understand, it's so strange. In your opinion, what could be the difference?

However, the Amiga is still very unstable. So my problem wasn't only the poor PSU... :boohoo:

At the moment this is my configuration:

- A1200 rev 1D4 (I've removed E123C and E125C component as suggested in all website).
- ROM 3.1
- Apollo 1240 w/ 32MB Ram
- Elbox Fast-ATA PowerFlyer Mk.II w/ HD 3.2 GB and Pioneer DVD-R 106

The computer is fully stable only when I use the original configuration.
If I add only the Apollo, it seems to work but sometimes reboot.
If I add only the Fast-ATA, it works quite well but continues to reboot in random way.
If I mount both the Apollo and the Fast-Ata... well, this is the most funny moment: red screen, yellow screen, black screen (sometimes with horizontal bands) or it could have also a normal behaviour for some minutes but after it reboot.

Why??? :boohoo:

I'm trying everything... and after every test I'm always more confused.  :-o

Any suggestion?

I'm been out from Amiga world for many years and now I've lost my familiarity with this system, specially in the hardware side. So I really don't know what I have to do  :-(  ... and I'm afraid of burning the 1200 motherboard or some expansion card.

Alex

[Karlos]

@starf81

Powering the A1200 motherboard via the floppy port is pretty common. My A1200T's motherboard is powered from the case PSU via this and also via all 5 voltage rails of the rear connector (most people just use this for the -12VDC line).

Naturally all other drives / fans are powered direct from the PSU too.

With this dual connection arrangement, less current has to flow throught any single point on the motherboard. Some accelerator cards (eg my BPPC 040 + BVision + RAM) can require quite some power, more than I would feel comfortable pumping through my ageing A1200 motherboard via a single place.

[starf81]

@Karlos

Just tested.

It's the same: Fast-Ata with Apollo don't start, without the Apollo, my 1200 can load the WB but it crashes after few seconds.

Could the Fast-Ata not working well without an accelerator card?

Alex

[Karlos]

starf81 wrote:

Could the Fast-Ata not working well without an accelerator card?

Possibly; I don't know for a fact. The Fast ATA probably doesn't give any real speed up on a bare 020 A1200 with no fast ram anyway and I doubt the creators of the hardware envisaged it being used in such a fashion.

[starf81]

Well... just tested again the 1200 with Fast-Ata and Apollo. It started, loaded the WB and after about 30 second the green power led blinked... another crash.

I'm going mad :crazy:

Alex

[patrik]

@starf81:

Why not just use the A500 PSU you said worked?


/Patrik

[Framiga]

Try to connect the Apollo NOT fully inserted  (pull it ~1mm out).

Sometimes the edge connector, lacks in contact.

btw . . now how much is the +5 volt rail? (measured on the Apollo)

[Jabaruk1]

Its your lucky day i,ve a AT psu wired with an amiga cable which powered a A1200 Tower with 040 and extra,s ,the towers sat doing nothing as i got a compact flash to ide converter and dont need a big psu anymore, mail me if ya want it jabar@jabar.karoo.co.uk :-)