A1200: now a PSU issue...

[Framiga]

unfortunately, the problem still with the UNUSED 3.3volt output, when used on an Amiga.

Some "cheap" ATX PSUs, when used on Amiga, gives unreliable output on the 5 volt rail (see at your 4.24 volt with Apollo installed).

Often (see at the ATX PSU specs) the 3.3 and 5 v power output, are given together (as total output Amperes)

When we use it on an Amiga, those ATX PSUs, works in an unbalanced way.

The solution, would be to use more reliable (more expensive ATX PSUs, with indipendently regulated output) or give to the PSU a "dummy" charge to the 3.3 volt output.

EDIT- erm . . . about how to achieve a reliable charge on the 3.3 volts line, any help wiil be apreciated :-)

A little personal note:

i own a PowerTower4000 (but its the same even on a PowerTower1200) with those little PCB with row leds-2 drive transistors and few polarization resistors).

Seen that i had the 3.3volt ATX output line there doing nothing, i have used it instead of the 5 volt to power the leds PCB (an easy way to dimm all those leds light).

Result . . . those very, very low power drain, from the 3.3volt ATX output, screws the whole PSU output (not so much but it does).

[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.

[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)

[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)