On Tuesday, February 11, 2003, at 05:30 PM, Bill Briggs wrote: > I've replaced the PMU board, thinking that it was the problem, but > the same things happen (though it did boot up once when the PMU board > was installed and the PM reset, but it wouldn't boot up a second > time). Today I measured the voltage on the PMU battery, and it > measured 5.6 volts. There are 6 cells so I'm thinking that the > voltage should be over 6 volts, close to 6.6 or so. But then since > the silicon runs at lower voltage, 5.6 may be enough to sustain it. I > guess what I'm looking for is someone who may know from experience > which board is the problem in this Mac, based on the symptoms, or if > I need to get a new PMU battery. I should mention that running off of > AC or battery made non difference. It wouldn't start. > > This unit had a board fail the first two weeks I had it, and Apple > replaced three boards (PMU, charge, power) and it worked for 4 and a > half years before the current failure. I've got a new Ti PowerBook > but I want this one back in operation for my wife. Any experience > based advice would be welcome.
the number of cells in the battery hasn't much to do with the actual voltage. traditionally, macs use about 5V or 5.5V of Trickle charge for boot purposes........ but this would be voltage coming from the Power Supply, not from the PRAM battery. For instance, on a G4 tower, I test for 5V (give or take a hair) on a lead direct from the power supply -- not from the battery. The backup battery in the Wallstreet is really only used to preserve PMU and RAM contents while the main battery is out, and the power adapter isn't plugged in. That is, it's what lets you sleep-swap main batteries. It has to be present, and have a charge, for the machine to boot. However, the machine should still boot even if it's pretty weak, especially if the power adapter is connected. If the backup battery causes any problems, it usually causes completely dead symptoms -- absolutely no power, no chime, NOTHING. You replaced the PMU board and that caused teh problem to disappear, if only briefly... this leads me to think that the PMU Board is what's causing the overall failure -- but that it's actually being shorted out by something else. So.... my guess is PMU Board AND logic board. Could also be processor, but I'd think not. -- G-Books is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Check our web site for refurbished PowerBooks | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> G-Books list info: <http://lowendmac.com/lists/g-books.html> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/g-books%40mail.maclaunch.com/> --------------------------------------------------------------- >The Think Different Store http://www.ThinkDifferentStore.com ---------------------------------------------------------------
