Dual G4 Will Not Power Up. Tried everything!!!!!!!!!

Discussion in 'Apple' started by savemydata, Mar 5, 2006.

  1. savemydata

    savemydata Guest

    Just was handed down a Dual g4/450/30gb 256 dvd plus studio display
    from friend who said it works but only sporadically. cannot start the
    machine. disconnected cord, changed cord to brand new one, press power,
    no light, no fans, changed battery, reset pmu switch one, reseatted
    ram, tried holding down apple ctrl pr and all that jazz. girl who gave
    it to me told me that sometimes it works and works great but then it
    wont go on again and then it goes on again a while later. any ideas???
     
    savemydata, Mar 5, 2006
    #1
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  2. savemydata

    spudnuty Guest

    No fan no lights sounds very primary like switch, line cord, power
    supply. This is from the G4 tech manual:
    Check for +5 V trickle voltage on pin 20 at the power supply
    connector. (Pin 20 is the pin closest to the edge of the logic board
    and the front of the computer.) If there is a +5 V reading, you know
    the power supply is likely OK. However, if there's no +5 V trickle
    power, replace the power supply.
    richard
     
    spudnuty, Mar 5, 2006
    #2
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  3. savemydata

    savemydata Guest

    Hi, I need to get a voltage tester to do this? Any recommendations on
    anything else I can try at my wits end with this thing.... if it had
    the .5v trickle thing what would that mean exactly>
     
    savemydata, Mar 5, 2006
    #3
  4. savemydata

    spudnuty Guest

    Yes you need to get or borrow at least a voltmeter. If the voltage is
    there that would normally mean the power supply is doing it's job and
    that it's good. Try unpluging the computer, then push the power button
    on the front wait 30 sec and try to boot. Continuing from the service
    manual:
    "Disconnect the keyboard and power-on the system via the power button
    on the front of the computer. If the unit powers on, replace the USB
    keyboard. If not, go to next step. · Power Mac G4 (AGP Graphics):
    Refer to "Resetting the PMU on the Logic Board" in this chapter to
    reset the PMU. · 8 Replace the logic board.
    Important: Be very careful when handling the main logic board.
    Remove the battery when handling the logic board so the PMU is not
    affected. The PMU is very sensitive and touching the circuitry on
    the logic board can cause the PMU to crash. If the PMU crashes, the
    battery life goes from about five years to about two days if the PMU
    is not reset. The PMU chip is located on the underside of the logic
    board at U20; refer to the Power Mac G4 (AGP Graphics/ Gigabit
    Ethernet) Logic Board Diagram for the location of the PMU button. Many
    system problems can be resolved by resetting the PMU chip. Whenever
    you have a unit that fails to power up, follow this
    1. Disconnect the power cord and check the battery in the battery
    holder (BT1). The battery should read 3.3 to 3.7 volts. If the battery
    is bad, replace the battery, wait ten seconds, and then reset the PMU
    (refer to the next step). If the battery is good, go to the next step.
    2. Press the PMU reset switch (S1) once on the logic board and then
    proceed to step 3. Do NOT press the PMU reset switch a second time
    because it could crash the PMU chip. 3. WAIT ten seconds before
    connecting the power cord and powering the computer on. If the
    computer powers on, go to the next step. If the computer does not
    power on, there is something else wrong with the computer; refer to
    the symptom/cure chart, "System" in this chapter. "
    I could send you the pdf.
    Richard
     
    spudnuty, Mar 5, 2006
    #4
  5. savemydata

    savemydata Guest

    Just cant get it to work... Can someone please tell me, does the G4
    have a light anywhere on the mobo that says its receiving power b/c i
    dont see any. in that case it would be the mobo and if not it would be
    the ps/ right?
     
    savemydata, Mar 5, 2006
    #5
  6. savemydata

    zwsdotcom Guest

    If you expect to debug this further, BUY A MULTIMETER and perform the
    tests recommended. $20 or less at Sears (near automotive, usually) and
    you are on your way.

    Madness is doing the same thing over and over again and expecting
    different results.
     
    zwsdotcom, Mar 5, 2006
    #6
  7. savemydata

    spudnuty Guest

    Yes it's right to the right of the last memory slot. Do those power
    supply first.
    Richard
     
    spudnuty, Mar 5, 2006
    #7
  8. savemydata

    Tim McNamara Guest

    From what you've wriotten, my thought is that it means you should take
    the computer to a qualified repair person. The odds are excellent
    that the power supply is dead or dying and needs to be replaced. If
    you- like me- don't know how to test and replace it yourself, pay
    someone who does to do it.

    I'm always baffled when the electronically inept- like me- balk at
    paying a few hundred dollars to keep a multi-thousand dollar computer
    running correctly. Stuff breaks sometimes, that's just the nature of
    the 'verse.
     
    Tim McNamara, Mar 5, 2006
    #8
  9. In <>,
    While I agree with your recommendation that a repair shop should be
    able to fix the problem, it is hard to describe a dual-G4 (that is new
    to the current owner, and therefore doesn't have any precious data on
    it), as a "multi-thousand dollar" computer.

    What's it really worth? $300 - $500? Can't see myself spending over
    $150 on fixing it.

    AC
     
    Aawara Chowdhury, Mar 5, 2006
    #9
  10. Dual G4? Depending on the other specs, as much as $800. It's a fairly
    powerful machine (yes, yes, I know there are faster machiens out there),
    but this machine has potentially a lot of life left in it. Spending
    $150 for a power supply and getting 3 more years from it would be a cost
    of $50/year. Not a lot, really.

    -Stephen
     
    Stephen Adams, Mar 5, 2006
    #10
  11. savemydata

    Tim McNamara Guest

    Compared to the cost of buying a new computer? While the parallel
    isn't exact, it's like repairing your old car versus buying a new one-
    cheaper to repair than to buy new. OTOH computers do eventually
    become obsolete faster than cars do, which is where the parallel
    breaks down, but a dual G4 is far from obsolete.
     
    Tim McNamara, Mar 5, 2006
    #11
  12. A dual 450 has a red LED on the logic board that is lit when the G4 is
    on or sleeping but not when the Mac is off. It's state is not an
    indicator of a bad power supply. A fault in the logic board or the front
    panel board (with the power, reset, and interrupt buttons) will prevent
    the LED from coming on even if the power supply is good.

    Better to shell out $20 for a voltmeter before you start replacing
    components. If the power supply tests good, diagnosing and repairing
    this thing gets more complicated. In that case, contact a Mac user group
    in your area to see if there's anybody that does low-cost repair work on
    old Macs.
     
    Neill Massello, Mar 6, 2006
    #12
  13. savemydata

    savemydata Guest

    Sometimes, when reinserting the power cord I hear a slight electric pop
    does this mean anything at all?
     
    savemydata, Mar 6, 2006
    #13
  14. It's common to get some arcing at the power connector on these machines.
    If you hear a pop from the G4's audio speaker, that's unusual.
     
    Neill Massello, Mar 6, 2006
    #14
  15. savemydata

    savemydata Guest

    Ok so I have the voltage tester, but I dont know how to use it......
    should I connect the red cable to the + and the black to the minus or
    opposite, and the dial has OHM, MA, V and V~ I set it to V and 250 I
    put the black on 11 and red on 22 as suggested in
    http://docs.info.apple.com/article.html?artnum=95064
    got no reading am I doing something wrong here never used a voltage
    tester, dying to know if im dong it right THANKS
     
    savemydata, Mar 6, 2006
    #15
  16. savemydata

    savemydata Guest

    Ok so I have the voltage tester, but I dont know how to use it......
    should I connect the red cable to the + and the black to the minus or
    opposite, and the dial has OHM, MA, V and V~ I set it to V and 250 I
    put the black on 11 and red on 22 as suggested in
    http://docs.info.apple.com/article.html?artnum=95064
    got no reading am I doing something wrong here never used a voltage
    tester, dying to know if im dong it right THANKS
     
    savemydata, Mar 6, 2006
    #16
  17. savemydata

    savemydata Guest

    I dont think I'm doing anything wrong and I can't seem to find any
    power voltage at all on this G4. I'm going to assume I need a power
    supply?
     
    savemydata, Mar 6, 2006
    #17
  18. savemydata

    savemydata Guest

    Given up, posted the mac on overstock auctions.,..
     
    savemydata, Mar 6, 2006
    #18
  19. Sounds like Mike Conrad found another name to use to post clueless "Help
    me" threads.
     
    Michael Vilain, Mar 6, 2006
    #19
  20. savemydata

    Tim McNamara Guest

    Hence my recommendation to PAY A PROFESSIONAL the paltry few dollars
    to get the problem diagnosed properly.
     
    Tim McNamara, Mar 6, 2006
    #20
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