A1200 boot problem - help!

[Buzzfuzz]

http://pinouts.ru/Power/atxpower_pinout.shtml
 
So wire them up to 14 and 15 an that should start the ATX PSU.
 
Franko was a bit faster, this for older ATX models

[Buzzfuzz]

Hmm, you could try to remove the SCSI kit and see if it will boot on it's own with the 1260.
Best thing is start blank and then each time add something to it, something could not be working.

[Buzzfuzz]

Ok.
 
So, I go to the local Best Buy to get an ATX PSU. I notice that none of them have the 6-pin AUX connector that my A1200 power adapter cable needs (I later found it was phased out in 2003 when additional pins were added to the main power header). I get one anyway, knowing I can solder the needed cable on.
 
I get home, open it up. Nice pre-wrapped cables coming off of it. So, I get to it. Get the pinout diagrams up and start stripping, wrapping, and soldering. I install it in the tower and turn it on to test.
 
I hear no fan.
 
Whaat? I try again. Nothing. After a few more tries I look into the supply thru the back fan grille. I see the plastic fan blade disc is lying loose, having broken out of the fan mechanism!!! So I could normally take this right back for a replacement -- but I sliced and soldered onto it already!!! $59 power supply. ARGH.
 
I then notice that there's 2 fans in the PSU. One is at the input inside the case, and then there's the broken one at the rear grille. I turn it on again and see the internal fan DOES spin, but it nearly silent. So I ignore the main fan issue for now (will open and try to fix or attach case fan to outside of case to pull air) and, now that I can tell when it's working with that internal fan, and wire it up to the Amiga.
 
Power on -- NO GO. Blip, then off -- just like the other PSU. So then I disconnect the main A1200 power input, wire up other peripherals to the PSU -- but FORGET to remove the A1200 floppy power feed. I turn it on -- PSU works, fan turns, and the Amiga does the color flash and seems to behave as before -- cycling black screeens (reboots) -- the Amiga is operating on the floppy input alone it seems!! WTF??
 
This is a 450W Thermaltake PSU. There is NO WAY the A1200 with main connector wired in can draw more than that. So did something die on the mobo that is shorting the PSU out??? If so, what is likely?? I see no cap leaks or bulges.
 
Is this A1200 done? I got this mobo NEW in 2004.
 
Sigh.
 
 
 
 
blakespot

Take the A1200 mobo out of it's tower.
Lay it on a table (avoid metal of course) and then have nothing on it, no keyboard, no drive, just plain the board, after some 30 seconds or a bit tad more you should see the kickstart screen.