Repair Power Mac G3 B&W PSU

[Angel]

Hi, a guy gave me a Blue Green G3 which doesn't power on.
In a first time, the computer powered up but didn't give any signal on monitor; after some other try neither the rest of hardware wanted to power up.
I think (hope) it's only the psu but i don't know if it is a standard atx (so i can replace with anything from pc world) or not.
Do u know anything about it ? The electric connector is the same or someone in cupertino played changing position to voltages ? And about the psu form factor ?

Thx

[Protools5LEGuy]

I think they were different.

https://allpinouts.org/pinouts/connectors/power_supply/power-mac-g3-mainboard-power-supply/
 

Pin   Signal   Color
1   +3.3V   Orange
2   +3.3V   Orange
3   GND   Black
4   +5V   Red
5   GND   Black
6   +5V   Red
7   GND   Black
8   +3.3V   Orange
9   +5Vsb   Purple
10   +12V   Yellow
11   +3.3V   Orange
12   -12V   Blue
13   GND   Black
14   Power On   Green
15   GND   Black
16   GND   Black
17   GND   Black
18   GND   Black
19   +5V   Red
20   +5V   Red

https://allpinouts.org/pinouts/connectors/power_supply/atx-motherboard-power-20-pin-ver-1x/

1   +3.3 VDC   Power +3.3V   orange      
2   +3.3 VDC   Power +3.3V   orange      
3   GND   Ground                   black      
4   +5 VDC   Power +5V   red      
5   GND   Ground                   black   
6   +5 VDC   Power +5V    red      
7   GND   Ground                   black      
8   PWROK   Power Good    grey      
9   +5 VSB   +5V Standby   purple      
10   +12 VDC   Power +12V   yellow   
11   +3.3 VDC   Power +3.3V   orange   
12   -12 VDC   Power -12V        blue   
13   GND   Ground                      black   
14   PS-ON   Remote Power ON/OFF  green   
15   GND   Ground                      black   
16   GND   Ground                      black   
17   GND   Ground                      black   
18   -5V   Power -5V                  white   
19   +5 VDC   Power +5V         red   
20   +5 VDC   Power +5V         red   

[Protools5LEGuy]

Check https://www.applefritter.com/node/21786 and try to use The WayBack Machine/Internet Archive for those broken links.

AFAIK G3 B&W and G4 Sawtooth are the simplest to DIY mod an ATX PSU

[Protools5LEGuy]

http://atxg4.com/sawtooth.html

Claims it works for G3 B&W and G4

[Protools5LEGuy]

Maybe just splitting pin 18 cable in 2, isolating the -5 Volts ATX voltage and wiring that half cable from pin 18 to ground (any from 15 to 17 pins should ) works, but don't quote me on this. And please wait for any other user to report.

Also to discard if it the PSU is still working you should try:

 To reset Parameter RAM or P-RAM

 To reset CUDA button on motherboard

 To test the Battery on Motherboard all PowerMacs have AFAIK

ADDED LATER


https://web.archive.org/web/20160614231459/http://xlr8yourmac.com/systems/MacinPC_ATX_case/Blue_G3_to_ATX.html

[Protools5LEGuy]

ATX Power
The B&W G3 uses a power supply that's almost but not quite identical to an ATX supply.  The lone difference is that the wire which supplies -5V on an ATX supply (pin 18) becomes a ground wire in the B&W G3.  If you just plug in an ATX supply without any modifications, you'll short out its -5V output.
One way of dealing with this is to simply remove the original ATX supply from the PC case and substitute the supply from the B&W G3.  However, this means that you can't take advantage of the 300W or bigger ATX supplies, one of the reasons to do an ATX conversion in the first place.

The other solution is to snip or remove the -5V wire from the ATX connector.  Actually, I found an ATX power extender cable at a PC store, and snipped the -5V wire on that instead, to avoid permanently altering the power supply's own wiring.  You'll likely need an extender cable anyway. (I had a link here to a 12in long PCpower & cooling extension cable but they no longer list it. Check local stores or the web/ebay for these, they're very cheap.-Mike)
The G3 motherboard's power connector is all the way at the bottom of the case, and few PC ATX supplies have a power cable long enough to reach.  Here are pictures of the female and male ends of the extender with the -5V wire snipped out.

ATX Side



G3 B&W Side

The -5V wire on an ATX supply is normally the only white wire in the cable, but don't count on it.  I downloaded the ATX spec the other day, and it was pretty careful to note that the color scheme was only a recommendation, not a requirement.  Make sure you snip the wire using the photo on the left as a reference.

Here's a picture of the modified extender cable installed in the system.

[Angel]

This one is from wikipedia:



Massa = GND
Abilitazione = Power on


and this from G3 B&W manual



They look same

If can i find the original delta's psu datasheet...

[IIO]

no, it has the same difference than on the atxg4 website

0 0
0 0
0 0 (Ground instead of -5V)

[Angel]

The original image from wikipedia was about an atx with 4 more pins (the longer and younger one): i've cutted the last two rows so the pin numbers on the right must be shifted by 2

https://it.wikipedia.org/wiki/ATX_(standard)

It seems the pins are correctly coupled but i don't have informations about the notch on the right in apple manual.