WON'T POWER ON: PowerBook Wallstreet PDQ

[JDW]

I have two PowerBook Wallstreet PDQ notebooks that once worked fine several years ago), but now neither will power-on when I press the POWER button (long or short press).

When I first plug-in the Apple AC Adapter, the fan spins at full blast and the green power LED lights for a couple seconds, and then the fan and LED power off. After that, pressing the power button does nothing.

I have no working battery anymore, so I only have AC power from the stock adapter. I've tested both PDQ machines with nothing in either drive bay and with even the hard drive removed, but to no avail. Both PDQ machines respond in the exact same way — power button doesn't power them on, despite my hearing the fan spin and LED light initially after connecting the AC Adapter. I've swapped their CPU cards, but again, it doesn't resolve the problem.

Here's a video overview of what I explained and mentions a couple voltage measurements I made too...

Wallstreet repair experts...
How can I fix these machines?

 

[S. Pupp]

It's been almost a month since my last post, so I want to provide an update so as to hear your kind thoughts.

ONE PDQ NOW POWERS ON RELIABLY​

First, I've been testing one of my Wallstreet PDQ machines almost daily (the one with a 266MHz CPU card). For much of September, I left the stock Apple AC Power adapter connected to the wall socket and to my PDQ. What I found after several days was that it would regularly power-on when I pressed the Power Button. No need for any PMU reset. It just worked. That only applies to one of my two PDQ machines, but at least one of them powers on well now (so long as the AC Adapter is left connected to the wall and PDQ).

However, the main problem has been that the machine suddenly powers off (loses power) after a while. And that span of time varies, almost like it is random. Sometimes, I can use it for 1 hour before it suddenly powers off. Other times, it's a half hour. There have been times when it was more than 1 hour. And yes, it still happens even if I keep a floor fan on the machine to ensure heat is not the issue.

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MY OTHER PDQ REFUSES TO POWER ON​

My PDQ with 300MHz CPU card refuses to power on even if I put the 266MHz card in it and swap RAM and even remove the main Hard Drive and keep both drive bays empty. I left the Apple AC Adapter connected to it and the wall socket for days last month, but to no avail. Even with the new 24V Adapter, it still won't power on. The hard drive works, despite having shown signs that something liquid had spilled on it in the past. I can put that drive in my other PDQ and it boots. So perhaps something spilled on the drive while the 300MHz PDQ was powered on in the past and that shorted something, but clearly not the hard drive, even though I see the liquid flowed under the drive and onto its PCB. I'm not seeing any burn marks on the machine's main PCB, however. Not sure what's wrong with this machine.

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MODERN AC ADAPTER TESTING​

I purchased this modern 24V 2.5A Adapter from Amazon, and I recently received my ZigZagJoe order which contained the adapter plug from Bix Power. (I had the plug shipped to him, and he kindly shipped it to me with my NuCF order.) No need to keep this connected to the wall or the PDQ, I'm pleased to report! The adapter will reliably power-ON one of my PDQ machines without fail! So I guess the improvement must come from bad caps inside the stock Apple AC Adapter, which is only overcome if you leave it connected all the time. The same is true of the G4 Cube power brick -- it often fails to boot the Cube unless you recap.

Sadly, this modern AC Adapter does NOT resolve my sudden power loss issue. As was true of the stock adapter, this new adapter too fails to keep the machine alive all the time. Sometimes it powers off after 1 hour, and sometimes less. (When I say "power off" I mean "loses power suddenly.")

When the machine loses power, if I press the power button soon afterward, it often fails to boot chime or show any signs of life. But if I wait 15 minutes or more, it sometimes powers on. That was true of the Apple adapter and this new one too. I've tested that over and over.

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WHAT I'VE TRIED​

CPU CARD SWAP​

I am able to put the 300MHz CPU card into my PDQ which has a 266MHz card, and the 300MHz card works just fine. But the sudden power loss problem remains.​

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RAM SWAP​

I have used 8-chip and 16-chip RAM Cards, but the power loss problem remains.​

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CONTACT CLEANER​

I have used DeOxit D5 on the CPU Card connectors and the RAM socket connectors, but the suddenly power loss problem remains.​

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EMPTY DRIVE BAYS​

I've tested extensively with nothing in either drive bay, and with the Apple CD-ROM in the right drive bay. Made zero impact on the machine. Sudden power off issue remains.​

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PMU Reset​

Does not fix the sudden power off issue.​

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BATTERY (in the distant past)​

In the past, when I had a good main battery, I don't recall ever experiencing this sudden power loss problem (when the main battery was inserted and charged). It's only now that I have no main battery at all that I have the power loss issue.​

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SLEEP MODE​

If I put the machine to sleep (while booted into OS 9.2.1), I can come back the next day and it wakes just fine. But I cannot leave it powered and awake for more than an hour or so before that power loss problem occurs.​

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SOLDER JOINTS​

I re-soldered the joints on the main DC input plug in the past, but that was never a solution for me.​

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PRAM BATTERY​

I confirmed that PDQ machines will indeed boot WITHOUT any PRAM battery installed at all. Mine was dead, so I removed it. Presence or absence most likely has nothing at all to do with the sudden power loss problem.​

RECAPPING​

I still think the electrolytic capacitors that are on the PCB which sits between the two drive bays are too far away from the primary DC board that has the DC input jack on it (at the back of the machine). I therefore am highly skeptical if that would be "the magic fix" for this sudden power loss problem. Nevertheless, to avoid a situation where folks continue to point to finger at those caps, I will need to now buy the caps and see what happens.

YOUR THOUGHTS​

Now that you've read my report, I'd certainly appreciate your thoughts and suggestions.
If I recap and still have the same power loss issue, then it's clear something else is the cause.
THANK YOU!

I agree with recapping, even if it does not seem clear how it would fix the problem. Recapping has solved some odd malfunctions that were difficult to diagnose in some of my older Macs.

 

[JDW]

I agree with recapping, even if it does not seem clear how it would fix the problem. Recapping has solved some odd malfunctions that were difficult to diagnose in some of my older Macs.

I am currently waiting for Mouser to get their act together regarding backordered items. The last backordered item won't arrive until Oct. 19th, so I will place my order then and hopefully nothing else will go out-of-stock before then.

But again, my gut tells me that recapping won't solve this problem because on that large physical distance of those caps from the main DC board at the back of the machine. Caps sit between the two drive bays to keep voltage levels from falling when drives in those bays suddenly power up (like the CD-ROM drive). The caps make sure the power to those drives remains stable. There are no electrolytic caps at the back of the machine where you connect your external power brick. Instead, that board uses tantalum and ceramic types, which have a solid electrolyte and do not need replacing.

So I am 90% sure a recap won't resolve the sudden power loss one of my PDQ machines has, nor will it likely fix the other PDQ which refuses to power on (even though a PMU reset does make the fan spin as it should).

So for the time being, let's pretend I've recapped the machines and still have the same issues. Would any of you have thoughts about the root cause in that case?

 

[S. Pupp]

If not done already, I would evaluate for barrel plug PCB failure by exchanging the barrel plug PCB's between the two PDQ's:

- If the booting behavior follows the exchange (i.e. the non-booting PDQ now boots and the booting PDQ now doesn't boot), then the problem is the barrel plug PCB of the non-booting PDQ.

- Unlikely, but if the booting behavior AND the sudden shutdown issue follow the exchange, then there is a problem with both barrel plug PCB's.

What brought this to mind was a non-booting Lombard I obtained last month that turned out simply to have a bad barrel plug PCB.

 

[Knife Cult]

Schematics would help, but a problem that fixes itself as you described sounds like a bad cap. Is this the board in question:


I think that board generates the different voltages used by the machine from the main battery and/or the power brick. If you carefully probe the caps on this board with the power brick attached, you should find constant 24v from the brick as well as 5v trickle/standby that goes to the cuda/PMU. If moving this board from the now-working machine fixes the still-dead one, that could help narrow the search.

Is there a 10v 100uF electrolytic next to the cuda/PMU chip? Is this near where the clock battery plugs in?

One other thing to try could be temperature. Without going to extremes, you could try different temperatures, like a warm sunny spot vs 15min in the fridge. If 15min in the fridge breaks the now-working one, that would also point to electrolytic caps.