nota33133 Posted November 17, 2017 Share Posted November 17, 2017 12.1 imac late 11 21.5 my power supply is suspect as it is only outputting 11,87v dc not 12v or over 12 and no output on the 5v pin #3 at all [at least on the same year 27'' model pin out the only one found] do we have any power supply experts ? or successful fixes [which cap to replace for 5v or cold solder joints locations] or diagram of the power supply internal circuits ? or even a real exact pin out of my unit [ I only found one for a same year 27'' imac] new the apple P/S is 150 with shipping rebuilt 100 used 29 to 50 on e-bay free ship while a new pc unit 200w is 20 or so for the same power and I even have a used pc unit to take apart but as I donot know if my yardsale find imac has other problems I am trying to fix the power before spending on the P/S only to find if it fried the MB or other bits in the process I found I have no idea how the first step the power button ''works'' as the P/S is hot powered on on some 12v pins all the time with ac in not really controlled by the power button Link to comment https://www.insanelymac.com/forum/topic/329743-apple-power-rate-is-1187v-dc-good-or-too-low-at-the-power-supply-out/ Share on other sites More sharing options...
nota33133 Posted November 18, 2017 Author Share Posted November 18, 2017 found this bit on an other mac board ''There are quite a few things that can be wrong for a board not to boot. You know you have 3.4V on G3Hot so that is a good start. I would next check to make sure the 3.3V supply is putting out 3.3V. It is a dual port device with the other half putting out 5V but 5V is not enabled until later in the power up sequence.'' now that brings my 3.0x v reading on pin#6 that should be 3.3v in to question but what I do not know is if it powers up later like the 5v bit looks to do of course if I am reading it right and IF he is correct about the 5 v power up sequence Link to comment https://www.insanelymac.com/forum/topic/329743-apple-power-rate-is-1187v-dc-good-or-too-low-at-the-power-supply-out/#findComment-2536675 Share on other sites More sharing options...
nota33133 Posted November 20, 2017 Author Share Posted November 20, 2017 is there a better place to ask for a pin out of my imac like a forum where they actually fix or repair imac's ? Link to comment https://www.insanelymac.com/forum/topic/329743-apple-power-rate-is-1187v-dc-good-or-too-low-at-the-power-supply-out/#findComment-2537560 Share on other sites More sharing options...
nota33133 Posted November 24, 2017 Author Share Posted November 24, 2017 after turkey day bump in hope of ?anybody know a trick to turn on a power supply out of the computerso I can test the power levels withOUT risk to the M/B or other bitsand see if it really doesNOT out put 5v at alland to check out the PC P/S before hooking it up to the imacdoes apple really use one ground pin for all volts 3.3 5 and 12 v pin #1 on my power supplyand no negative 3.3v or 5v at all ?what would happen if I used a PC p/s to feed 3.3 5 and 12v on the apple imacas I have several from older PC's so a no cost test if it will not damage the imachow to wire the separate grounds on the PC p/s to the apple imac ?is a PC start switch the same as the imac ''power button'' ? the front push button not the a/c switch on the actual p/s boxwill the imac signal start a PC P/S ? or is apple different just to be apple different ?is the 3.3v line apple calls signal send a code or just voltage back to the power supple at start button push ? __________________ Link to comment https://www.insanelymac.com/forum/topic/329743-apple-power-rate-is-1187v-dc-good-or-too-low-at-the-power-supply-out/#findComment-2539051 Share on other sites More sharing options...
LouCioccio Posted November 24, 2017 Share Posted November 24, 2017 You will need to make a dummy load and a momentary switch now I do not know the pinouts for the iMac, anyway the dummy load or even a resistor for a load should work. Lou Cioccio Link to comment https://www.insanelymac.com/forum/topic/329743-apple-power-rate-is-1187v-dc-good-or-too-low-at-the-power-supply-out/#findComment-2539073 Share on other sites More sharing options...
nota33133 Posted November 24, 2017 Author Share Posted November 24, 2017 thanks apple ''power/start switch is a momemtary switch on what voltage does it control ? is a PC push button the same kind of a momemtary switch [ the front panel one not the on the power supply on/off switch] can I swap them have several PC push button switchs if the PC P/S is also to be tested before use what pins gets the dummy load and ground ? i have eazy access to PC pinouts and have PC power supplys on hand found a 27 '' same year imac pinout but do not know if the 21.5 has the same pinout idea is test the apple imac PS first by first test the switch if good if it is bad try PC button switch then try to test the power supply in the imac if good fine if bad then try to replace crude and rude with an exterior PC PS wired thru a hole in the back to the correct apple p/s out pins to see if the M/B or other bits are working before spending on a new apple power supply $150 for china built ? a pin out sure would help of the PS on my 2011 imac 21.5 Link to comment https://www.insanelymac.com/forum/topic/329743-apple-power-rate-is-1187v-dc-good-or-too-low-at-the-power-supply-out/#findComment-2539168 Share on other sites More sharing options...
LouCioccio Posted November 25, 2017 Share Posted November 25, 2017 thanks apple ''power/start switch is a momemtary switch on what voltage does it control ? Yes but I do not know what voltage it controls. is a PC push button the same kind of a momemtary switch [ the front panel one not the on the power supply on/off switch] can I swap them have several PC push button switchs Yes it just momentary so any switch would work. if the PC P/S is also to be tested before use what pins gets the dummy load and ground ? i have eazy access to PC pinouts and have PC power supplys on hand found a 27 '' same year imac pinout but do not know if the 21.5 has the same pinout You may have to Google more what I don't know if those connectors are the same Lou Cioccio idea is test the apple imac PS first by first test the switch if good if it is bad try PC button switch then try to test the power supply in the imac if good fine if bad then try to replace crude and rude with an exterior PC PS wired thru a hole in the back to the correct apple p/s out pins to see if the M/B or other bits are working before spending on a new apple power supply $150 for china built ? a pin out sure would help of the PS on my 2011 imac 21.5 Link to comment https://www.insanelymac.com/forum/topic/329743-apple-power-rate-is-1187v-dc-good-or-too-low-at-the-power-supply-out/#findComment-2539217 Share on other sites More sharing options...
nota33133 Posted December 1, 2017 Author Share Posted December 1, 2017 You may have to Google more what I don't know if those connectors are the same Lou Cioccio of course they are DELIBERATELY different requiring me to desolder the exist power out connector off the p/s board [if more test proves the P/S dead or dying] and then solder on the pc p/s wires to old apple connector on another non computer [do it yourself car repair] board one guy who fixes apples claims there is NO 5v line on imac something I find odd as a ps for a PC uses a 1/2 dozen 5v lines to the M/B alone plus several for sata3 devises power usb ect lots of 5v everywhere still head scratching and digging info surprised not much fix it yourself for middleage imac's Link to comment https://www.insanelymac.com/forum/topic/329743-apple-power-rate-is-1187v-dc-good-or-too-low-at-the-power-supply-out/#findComment-2542273 Share on other sites More sharing options...
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