550c Cap Issue?

[LCARS]

Could this be a capacitor issue?

My 550c was running fine. I ran Apple Personal Diagnostics and no errors were reported. I shut down, plugged in my AppleCD 600 (with the Apple-branded PowerBook SCSI cable) and rebooted. All is fine- the computer starts, CD comes right up on the desktop, we're good to go. But when I reboot in this configuration, I get a Type 10 error on a few boots and Bus Error on others. The same problems after I removed the SCSI plug.

Then...death chimes. I pulled all power, waited 5 minutes, reset the power manager, and booted without the SCSI cable. Successful boot. Plugging it again caused the same series of problematic events. When I plugged in the SCSI cable to the powered-off machine, the speakers crackled. This makes me think that perhaps a capacitor somewhere along the line, is weak. I have not yet taken it apart to inspect. For another data point, the same drive and cable work fine on my IIci. I eager await the collective wisdom. Poor little machine :sadmac:

 

[Byrd]

I wouldn't say capacitors without doing usual troubleshooting; if getting death chimes I'd check the RAM module first; pull it and see if you get more reliability.  Reseat and clean the processor card and connectors.

The crackling from the speakers/SCSI cable is related to a ground issue, not important nor capacitors a cause.

 

[LCARS]

Thanks, Byrd. I'll inspect the connections. It could use a cleaning regardless, I'm sure.

Its strange: after resetting the power manager, it will boot just fine providing that I don't plug in the SCSI cable. Let's see what we find inside...

 

[Byrd]

It wouldn’t be a bad idea to check the SCSI device as well; make sure the device is properly terminated, jumpered and the PSU in that outputs +12V cleanly

 

[LCARS]

Thanks, Byrd. I've got an update that unfortunately, hasn't given me many answers. The CD-ROM works perfectly with my other machines and I don't have a multimeter here to test a clean +12V.

I checked the HD and RAM connections and they look properly seated. With both (discharged & unresponsive) batteries installed, I plugged in my Farallon Ethernet adapter and as soon as the other computer appeared on the desktop, the machine would shut off. Once was what appeared to be sleep and the other was to off.

After removing the batteries, it has shut off only once. I think its safe to assume that the PRAM battery is toast and is probably playing a role in this. Do the caps in this series have a known history of going bad?

 

[LCARS]

Addendum: I was able to boot from the external SCSI to load 7.6.1. The machine crashed during installation during installation of "Finder." I rebooted from the CD and was given a Bus Error bomb again. Then on the 3rd try (still booting from CD), it froze during start up. I'm tempted to try again tomorrow but given how these problems seem to keep appearing, I'll wait to hear from the collective (pretty please!)

If not failed caps, bad hard drive? Please don't say, "bad RAM." :simasimac:

 

[AlpineRaven]

The only Caps is around where the PSU are but I haven't came across to leaked ones of 500 series.

BTW 550c is same logicboard as 540c.

Cheers

AP

 

[Franklinstein]

Remove the PRAM battery entirely. A weak battery can cause power manager corruption which will result in weird problems from time to time. A missing battery causes no problems unless you try to sleep-swap main batteries or something. 

If the main batteries have leaked at any time and the leak has not been cleaned up, you may experience problems since that stuff is often conductive. 

BTW 550c is same logicboard as 540c.

Mostly, but there are a few differences including the fact that the 550 has "PowerBook 550c" printed on the board under the floppy drive, and something regarding the display connector that makes them incompatible. Though the connecting cables are the same, something about the display intermediate board in the 550c is very different from the rest of the 500 series, preventing a head-swap from a 550 to a different model.

 

[AlpineRaven]

Remove the PRAM battery entirely. A weak battery can cause power manager corruption which will result in weird problems from time to time. A missing battery causes no problems unless you try to sleep-swap main batteries or something. 

If the main batteries have leaked at any time and the leak has not been cleaned up, you may experience problems since that stuff is often conductive. 

Mostly, but there are a few differences including the fact that the 550 has "PowerBook 550c" printed on the board under the floppy drive, and something regarding the display connector that makes them incompatible. Though the connecting cables are the same, something about the display intermediate board in the 550c is very different from the rest of the 500 series, preventing a head-swap from a 550 to a different model.

I have swapped both boards to 550c and 540c - works both ways.

Cheers

AP

 

[Franklinstein]

Interesting that you got it to work. Maybe you had different revisions? I know the rest of the 500 series had two distinct logic boards but I'm pretty sure the 550 only had the one. I don't have any 550s in need of service at the moment and I'm not inclined to tear a good one apart to verify.

 

[techknight]

the 550 had a different CPU card if I recall. Anyways.

This all sounds hallmark of either non-clean power coming from the AC adapter, or, bad RAM. or even Cache if it has a PPC CPU. 

Bad RAM will cause all this nonsense. and I suspect that over anything. 

on a 68K, a bus error is triggered when the CPU doesnt get a DTACK back on peripheral accesses. This can happen if the peripheral isnt responding, or, if the "address" this peripheral is at is incorrect. Such as if the address value pointer was corrupt or incorrectly passed into the CPU/Driver/Software. 

 

[LCARS]

I clearly lost track of time entirely. Thank you for your replies. If the RAM is indeed the problem, I do have a 540c that could lend its RAM for a test.

To the best of my memory, all three 5xx models used the same power adapter. Is that correct?

Ok, off to build up the courage to open up two classic machines :-O

 

[Crutch]

The 540c and 550c at least used the same AC adapter. I’m not sure about the others first hand. But probably. 

 

[LCARS]

Thank you, Crutch. If the brick that came with my 550 is the original, it matches the OE brick of my 540c.

Update:

I swapped the RAM from the 550 to 540 and so far so good. There haven't been any of the issues the 550 was experiencing. It's a 32MB module, so I hope it's not faulty.

So, does that leave the CPU and/or hard drive as suspect in the 550? I'm using the power brick that was in use during the 550 issues, on the 540 and smooth sailing there, too.

The HDD is Apple branded and properly seated. I'll re-seat the CPU as well. I'm wary to try to remove the PRAM battery as it requires more disassembly. Assuming it's not leaking, is a dead PRAM batt. as problematic on this model as it can be on others?



PowerPoint anyone? The 'Quick Preview' was an ironically perfect outline for what PP presentations have become.

 

[Byrd]

I'd suspect the internal HD now throwing up such quirky errors - can you pull it, and run an OS, software off an external drive?

 

[LCARS]

Thank you, Byrd. I can pull it and swap again with the 540 for another test. My goal for the 550 is to be mobile so I'll be looking at the SCSI2SD adapter with a SLC SD card. One and done, hopefully. I'll miss the mechanical sound.

 

[LCARS]

At last, a happy update! Instead of me telling the forum, how about the PowerBook?



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