A1200: now a PSU issue...

[starf81]

Well... just solved the Apollo's issue, my "A1200 project" goes ahead. And, obviously, I've another problem  :-D

Up to now, I've tested my configuration with an A500+ power supply but now I want to adapt an ATX one.

I had an old working 200W ATX power supply so I've adapted it using the original cable taken from the original A1200 PSU. I've found on the net some schematics to wire the ATX PSU to che Amiga cable: +12v, -12v, +5v and GND. After I've tested it with the A1200 and all work correctly.
But, as I attach the Apollo 1240, something goes wrong. The green power led is less strong, the screen is black and the fan wired to the Apollo's board turns slower.
I can't understand... I've tried two different ATX that work correctly with my PC. In addition, when I use the A500+ PSU, the Amiga and the Apollo work correctly.

Last note: to start the ATX PSU, I've linked the green "PS ON" cable with a black GND wire.

Could you help me?  :-D

THANKS!
Alex

[starf81]

Yes Karlos, only the 1240 and the mouse, no other devices or exansions.

I've taken the +12v line from the 4-wires molex as the +5v, while the -12v line comes from the 20 wires plug. Obviously I've tested them with a meter and are good.

In addition, as I said, I've tested two different ATX PSU, the old 200w and the 400w that I use everyday into my PC.

It's so strange... voltages are right and without the Apollo all work correctly. The Apollo works only with the A500 PSU.

Any ideas?  :-?
Alex

[starf81]

Tomorrow I'll measure voltages inside the Amiga. This is the only test I've skipped.

After I'll try also the audio quality and I'll let you know...

Thanks for your interest... this is a very strange case  :-o

Alex

[starf81]

Hi BlobRana. Why you said this? Help me to understand because I'm very confused  :-?

I've found several schematics on the net to use an ATX PSU. There are also circuits to turn on it with a switch as you can  do in a PC.
In addition, you can find on Aminet little software to turn-off the computer directly from the shell only with ATX PSU...

Thanks
Alex

[starf81]

I've just measured voltages from PSU and inside the A1200.

These are the values:

ATX PSU
-------

OUTPUT:
+ 11,68V
+ 5,15V

A1200 (without Apollo):
+ 11,95V
+ 4,58 V

A1200 (with Apollo):
+ 11,86V
+ 4,24V


A500+ PSU
---------

OUTPUT:
+ 12,00V
+ 5,31V

A1200 (without Apollo):
+ 12,35V
+ 5,15V

A1200 (with Apollo):
+ 12,61V
+ 5,00V

It's so strange...  :-?  :-o  :-?

The A500 PSU provides higher voltages than the 200W ATX PSU. In addition the ATX works perfectly inside a PC and, as I just said, I've tested another ATX PSU, that was a 400W.

Looking to the values, the main problem seems to be the +5V, that is too low when I attach the Apollo. Probably it needs more energy so the Amiga doesn't start.

... I can't understand  :pissed:

Alex

[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

[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

[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

[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

[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

[starf81]

Yes, I've already tried to check the edge connectors.

Regarding the +5, where can I measure it on the Apollo? I don't have a schemathic to identify the +5v rail. I can only find the +12 where I wire the fan.

Alex

[starf81]

Well, just changed the Apollo with a Blizzard 1260 all work correctly. Strange, very strange... the previous Apollo's owner confirms me that it works well on its machine.

However, now my A1200 is 100% working!!!

Thanks for your help!

Alex