8 Replies Latest reply: Nov 16, 2010 1:57 PM by old comm guy
makken Level 1 Level 1 (5 points)
When testing the power supply (1.8Ghz Powermac G5)for +5v trickle between pins 1 and 23 what is the voltage setting AC or DC?.

Power Mac G5 1.8Ghz Duel Processor, Mac OS X (10.5.1)
  • japamac Level 7 Level 7 (24,390 points)
    Hi-

    DC.
  • makken Level 1 Level 1 (5 points)
    Not getting any readings on DC at all, tried 2 different multimeters (followed instructions on how to test from the G5 manual, black on pin 23 and red on pin 1). The thing is i have two Mac G5's one working and the other non working, i get no readings at all with the known working one if i set my multimeter to VDC however i do get readings when set to AC so are you sure it is supposed to be set to DC, if the multimeter is supposed to be set to Volts DC then why am i getting no readings and i have gone through all the ranges, and the working power supply is ok because i have no problems with the mac working at all.
  • DaddyPaycheck Level 6 Level 6 (16,035 points)
    Are you supposed to be measuring under load?
  • makken Level 1 Level 1 (5 points)
    Yes you're spot on and i am a *******, i did'nt realise you were supposed to turn the switch on at the socket as the manual says connect the power cord but Don't turn on the computer and i thought it meant don't switch on at the socket (must of had a short circuit in my brain) anyway just tried it under load and is 5.09 Volts DC so is fine, so just gotta check the faulty one now, thanks.
  • old comm guy Level 4 Level 4 (2,235 points)
    makken wrote:
    Yes you're spot on and i am a *******, i did'nt realise you were supposed to turn the switch on at the socket as the manual says connect the power cord but Don't turn on the computer and i thought it meant don't switch on at the socket (must of had a short circuit in my brain) anyway just tried it under load and is 5.09 Volts DC so is fine, so just gotta check the faulty one now, thanks.


    We call that leaving the switch in the 255 position. You know: 0FF in hexadecimal.

    Trust me, you're not the first person to have done that. In fact, I may be suing for copyright infringement.
  • Rblooz Level 1 Level 1 (0 points)
    Hey makken, you mentioned in your post that you "followed instructions on how to test 'the power supply' from the G5 manual, black on pin 23 and red on pin 1". Can you tell me what G5 manual has this kind of information in it? Where can I get a copy? Thanks in advance!
    Rblooz
  • BDAqua Level 10 Level 10 (119,720 points)
    Hi Rblooz, and a warm welcome to the forums!

    G5 PSU pinouts...

    http://www.applefritter.com/node/6561

    Service Manual with take apart instructions...

    http://www.eserviceinfo.com/download.php?fileid=25193
  • old comm guy Level 4 Level 4 (2,235 points)
    The procedure is not actually in, say, the Service Source manual, although there are pinouts and corresponding pin assignment and wire color information in that document. There is no test procedure there, but procedures have been described in this discussion in the past three months.

    In general, when the supply is connected to AC, there is a +5V DC standby voltage on pin one of P1 (the 24-pin connector connects near the front of the case to the logic board). The standby voltage is on a purple wire. Ground pins are located at 2,4,8,10,11,13,15,17,19,21 and 23. The easiest measurement of the standby voltage is going between pins 1-13 (the two end pins of the connector that are populated, since 12-24 have no pins in them at the other end of the connector.