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From: spudnuty on 22 Jan 2006 21:02

Chris wrote:
> Wow! I can try cleaning it out again. All the fans
> spool up for a few seconds before it just stops dead in its tracks. The
> Apple P/N: 614-0157.
You could try resetting the PMU, This is from the mirrored door take
apart.:
"Resetting the PMU on the Logic Board The PMU (Power Management Unit)
is a microcontroller chip that controls all power functions for this
computer. The PMU is a computer within a computer. Its function is to:
· tell the computer to turn on, turn off, sleep, wake, idle, etc. ·
manage system resets from various commands. · maintain parameter RAM
(PRAM). · manage the real-time clock. Important: Be very careful
when handling the logic board. The PMU is very sensitive and touching
the circuitry on the logic board can cause the PMU to crash. If the PMU
crashes and is not reset, the battery life goes from about five years
to about two days. Note: For the location of the PMU reset button, see
"Logic Board Diagram" in the Views chapter. Many system problems
can be resolved by resetting the PMU chip. When you have a computer
that fails to power up, follow this procedure before replacing any
modules: 1. Disconnect the power cord and check the battery in the
battery holder. The battery should read 3.3 to 3.7 volts. If the
battery is bad, replace it, wait ten seconds, and then proceed to step
2. If the battery is good, go directly to step 2. 2. Press the PMU
reset button once and then proceed to step 3. Do not press the PMU
reset button a second time because it could crash the PMU chip. 3. Wait
ten seconds before connecting the power cord and powering on the
computer. If the computer does not power on, there is something else
wrong with it; refer to the "System" section of "Symptom
Charts" in this chapter. Note: The above procedure resets the
computer's PRAM. After resetting the PMU, be sure to reset the time,
date, and other system parameter settings."
Also here's the power supply verification procedure:
"Power Supply Verification To power on, the computer's logic board
requires a "trickle" power of +5V. If the system fails to power
on, first reset the PMU. Then follow the procedure outlined below to
determine whether the problem is related to the power supply. Note: To
verify the power supply, you need a volt meter. When connecting the
volt meter leads to specific pins, make sure the power supply remains
securely plugged into its connector on the logic board. The following
figure shows the pins and voltage on the computer's power supply
connector. (The color noted represents the color of the wire attached
to the pin.) 1. Plug a known-good power cord into the computer. Do
not turn on the computer. 2. Connect the black lead of the volt meter
to pin 12 of the power supply connector; connect the red lead of the
volt meter to pin 14. The volt meter should measure approximately
+25V. If you do not get a reading of +25V, recheck the volt meter
connections and measure the voltage again. If voltage is still not
present, replace the power supply. If you do measure +25V on pin 14,
the power supply is likely OK. Go to the next step for further
verification. 3. Check the trickle voltage by connecting the black lead
of the volt meter to pin 12 of the power supply connector; connect the
red lead of the volt meter to pin 1. The volt meter should measure
approximately +5V. If you do not get a reading of +5V, recheck the volt
meter connections and measure the voltage again. If voltage is still
not present, replace the power supply. If you do measure +5V on pin 1,
the power supply is likely OK. Go to the next step for further
verification. 4. Start up the computer by pressing the power button on
the front panel. If the computer starts up normally, the power supply
is OK. If the computer does not start up normally, go to the next
step. 5. Check to see if the power supply fan is spinning. If the fan
is not spinning, replace the power supply. If the fan is spinning, go
to the next step. 6. Connect the black lead of the volt meter to pin
12 of the power supply connector; connect the red lead of the volt
meter to pin 24. The volt meter should measure approximately +12V. If
you do not get a reading of +12V, recheck the volt meter connections
and measure the voltage again. If voltage is still not present,
replace the power supply. If you do measure +12V on pin 24, the power
supply is likely OK. Go to the next step for further verification. 7.
Connect the black lead of the volt meter to pin 12 of the power supply
connector; connect the red lead to pin 6. The volt meter should
measure approximately +3.3V. If you do not get a reading of +3.3V,
recheck the volt meter connections and measure the voltage again. If
voltage is still not present, replace the power supply. If you do
measure +3.3V on pin 6, the power supply is likely OK. Go to the next
step for further verification. 8. Connect the black lead of the volt
meter to pin 12 of the power supply connector; connect the red lead to
pin 3. The volt meter should measure approximately +5V. If you do not
get a reading of +5V, recheck the volt meter connections and measure
the voltage again. If voltage is still not present, replace the power
supply. If you do measure +5V on pin 3, the power supply is likely OK.
Go to the next step for further verification. 9. Connect the black
lead of the volt meter to pin 12 of the power supply connector;
connect the red lead to pin 10. The volt meter should measure
approximately +12V. If you do not get a reading of +12V, recheck the
volt meter connections and measure the voltage again. If voltage is
still not present, replace the power supply. If you do measure +12V on
pin 10, the power supply is OK and the testing is complete. You have
verified that the power supply is not the cause of the "no apparent
power" symptom.
pinouts:
Pin 23 GND Black Pin 22

From: spudnuty on 22 Jan 2006 21:14

spudnuty wrote:
>blah blah
Hmm didn't take the pinouts.
Pin 24 +12V YellowBlack, Pin 23 GND Black, Pin 22

From: Ralph Wade Phillips on 23 Jan 2006 09:17
Howdy!

"Chris" <cz1230(a)hotmail.com> wrote in message
news:JnSAf.34302$tK4.19585(a)tornado.ohiordc.rr.com...
> Wow! A huge thanks to all of you so far! I didn't expect this many
> replies. Here are some more details about it. I had checked it out to
see
> if it was dirty, and it looked pretty clean (also no charred components
when
> I glanced around inside). I can try cleaning it out again. All the fans
> spool up for a few seconds before it just stops dead in its tracks. The
> Apple P/N: 614-0157. It appears that there are no matches for this
machine
> out there at the moment (DigAudio, MDD, Sawtooth are all different!).
Also,
> the fans are all two wire as well, but if they are all working anyway I
> wouldn't suspect that to be the issue. Another issue is that I have been
> told it is remotely possible that the logic board is the problem instead.
> That is much more expensive, and still difficult to tell which is causing
> this strange problem.

I just had a machine come into the shop with the exact same
symptoms.

Try pressing the CUDA button for about 10 seconds with the power
unplugged, then see if it comes back up.

RwP


From: Andrew Tweddle on 30 Jan 2006 22:19
Chris wrote:

> Hi,
>
> I was curious if anyone has information on repairing a power supply for
> a PowerMac G4 733 (Quicksilver). I believe the supply has an issue as it
> won't start up the machine, but it spins the fans for a few seconds before
> shutting down. Any suggestions or information would be appreciated as the
> replacement is quite costly!
>
> Thanks,
> Chris
>
>
I had a Blue G3 machine which had a blown supply the form factor was
identical to an ATX. It had a blown main power FET which had a rating
IIRC of 700 Volts 10 Amps. I replaced with one that was 600 Volts 5 Amps
and it ran. The only other thing to bear in mind is that the wiring is
the same as an ATX however one of the supply voltages wasn't necessary ,
maybe -5V or -12V.

This site had quite a bit of info

http://www.xlr8yourmac.com/

Andrew
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