Pismo display issue.

[TheWhiteFalcon]

Found a 500MHz Pismo for $5 today. Got it home, removed the PRAM battery and it booted up. I was going through what was on the hard drive when the computer froze.

Since then, it will no longer boot up fully. I get the chime, followed by nothing else. As far as I can tell nothing on the display is happening. It also won't seem to output to an external over VGA. I've reset the power manager, the PRAM, and I've removed and reseated the processor, display cables on the logic board side, replaced the hard drive, etc.

Thoughts?

 

[MikeatOSX]

I would reseat the processor card tightly until I hear a "clack".

Or Power Supply Card faulty?

 

[techknight]

the hard freeze means you lost a voltage, or lost something on the bus. the data cant get to the video adapter, or the interrupts arnt firing anymore. 

 

[TheWhiteFalcon]

I've reseated the CPU a few times. Techknight, should I replace the sound board where the jack is, or the power board?

 

[MikeatOSX]

In contrast to different CPU cards the pismo CPU card should make a loud noise when reseated.

 

[techknight]

I would check the power supply card first, your probably missing a voltage somewhere. If the power supply card is good, then the next thing in line is the GPU. 

In order to get a chime, the computer "core" is functional. the Firmware boots, the CPU is executing code, and all of its busses are not held into contention by a bad IC somewhere. 

Since there is a chime, 90% of the computer works. However, because of the hard freeze, and now no video, the likely fault here is a voltage to the GPU, or the GPU itself. There are other peripheral devices on the bus, such as IDE/SCSI/USB etc.. that can go bad, but its not very likely. 

The firmware probably enforces initialization of the graphics subsystem, and if it doesnt respond it halts the boot process. Sorta like the imacs plagued with GPU issues, etc... does. 

The chip responsible for refreshing the LCD display itself is still good, or still had power, otherwise the screen would have slowly faded to white after the freeze. 

Now another thing it could be is the L2 Cache could have went bad. It will cause a freeze, and cause the machine not to start if its bad enough. 

 

[TheWhiteFalcon]

Okay. Is the GPU on the CPU daughter card, or on the logic board itself?

A 400MHz CPU module is pretty cheap from ifixit, and while I'd prefer to keep the 500MHz module I don't mind ordering it along with the power board.

Are the power boards interchangeable between the Pismo and Lombard?

 

[MikeatOSX]

No, they are not interchangeable.

 

[uniserver]

is the battery still installed?   i would remove the battery, 

 

[TheWhiteFalcon]

I've tried starting it without the battery and with only the battery. Same result every time.

 

[MikeatOSX]

PRAM battery disconnected?

 

[TheWhiteFalcon]

Of course. It wouldn't even chime if it had a dead PRAM battery.

 

[TheWhiteFalcon]

So, it may have been bad RAM. I removed the original 128MB chip and replaced it with a 32MB and 64MB set, and it works and is now running 9.2.1. I'm glad either way.

 

[CC_333]

Maybe reseating the CPU card is what did it?

Anyway, glad you got it working!

c

 

[TheWhiteFalcon]

Other than the fact I removed and reseated the CPU about five times previously...

 

[techknight]

Hmm strange. usually with bad RAM you get the crash sound. 

 

[TheWhiteFalcon]

Yeah, I'm not sure what's up with it. At any rate it hasn't given me one hint of trouble since I got it working, and I use it daily.

 

[techknight]

Good to hear.