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apple power rate is 11.87v dc good or too low at the power supply out


nota33133
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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

 

 

 

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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

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after turkey day bump in hope of ?

anybody know a trick to turn on a power supply out of the computer
so I can test the power levels withOUT risk to the M/B or other bits
and see if it really doesNOT out put 5v at all
and to check out the PC P/S before hooking it up to the imac

does apple really use one ground pin for all volts 3.3 5 and 12 v pin #1 on my power supply
and 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 imac
as I have several from older PC's so a no cost test if it will not damage the imac
how 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 box
will 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 ?

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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

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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

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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

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