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Quadra 950 - No Boot Chime (or boot)


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Howdy, everyone!

 

I just got ahold of a Q950 with a dusty, but other wise good looking, logic board that will not boot. The PSU appears to be putting out the correct voltages when powered on, so I think I can rule that out. Any display I hook up to it registers that a signal is being sent, but there's just no video. The speaker clicks loudly on power-up, but no chimes are produced. I've removed all the RAM and tried it with just what's onboard, but still no change in behavior. These beasts are entirely new to me, so I'm a bit lost where to go next; any advice would be greatly appreciated.

 

Also, there appear to be four DIMMs that I am assuming are the ROMs. They have no identification, so I have no idea if they are even in the correct slots. Is there a way to determine if they are? Alternatively, are they even ROMs?

 

Thanks much,

Will

Edited by warmech
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8 hours ago, warmech said:

Howdy, everyone!

 

I just got ahold of a Q950 with a dusty, but other wise good looking, logic board that will not boot. The PSU appears to be putting out the correct voltages when powered on, so I think I can rule that out. Any display I hook up to it registers that a signal is being sent, but there's just no video. The speaker clicks loudly on power-up, but no chimes are produced. I've removed all the RAM and tried it with just what's onboard, but still no change in behavior. These beasts are entirely new to me, so I'm a bit lost where to go next; any advice would be greatly appreciated.

 

Also, there appear to be four DIMMs that I am assuming are the ROMs. They have no identification, so I have no idea if they are even in the correct slots. Is there a way to determine if they are? Alternatively, are they even ROMs?

 

Thanks much,

Will

The q950 normally doesnt have a rom card installed unlike other apple products. It does have a slot for one though, which is located by the ram banks. 

 

The 4 dimms on the top side of the motherboad is the vram. Make sure the contacts are clean and leave them be. If all banks are occupied, it should be 4mb, which is the max vram the computer can handle. 

 

The computer will not boot with less than 4 sticks of matching memory. There are 4 banks for ram. Try installing the ram in bank A, which is 2 slots on the top row, and 2 slots on the bottom row. There should also be a silk screen on the motherboard showing which slots are for which banks.

 

Is the pram battery any good? I can't remember if the computer will boot without a good battery. 

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8 hours ago, Sir Foxx said:

The q950 normally doesnt have a rom card installed unlike other apple products. It does have a slot for one though, which is located by the ram banks. 

 

The 4 dimms on the top side of the motherboad is the vram. Make sure the contacts are clean and leave them be. If all banks are occupied, it should be 4mb, which is the max vram the computer can handle. 

 

The computer will not boot with less than 4 sticks of matching memory. There are 4 banks for ram. Try installing the ram in bank A, which is 2 slots on the top row, and 2 slots on the bottom row. There should also be a silk screen on the motherboard showing which slots are for which banks.

 

Is the pram battery any good? I can't remember if the computer will boot without a good battery. 

Regarding the VRAM/ROMS: good to know - thanks! :)

 

I've tried four sticks of matching RAM in every bank to no avail; I have a green light on the logic board, but still no chime or video. :( The PRAM battery is new - pulled from a working machine, so I know it's a good one - but it's also had no effect. For what it's worth, there is nothing attached to the board at the moment; it's just a bare board with a keyboard and monitor running to it.

IMG_1994.jpg

IMG_1993.jpg

IMG_1992.jpg

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8 hours ago, warmech said:

Regarding the VRAM/ROMS: good to know - thanks! :)

 

I've tried four sticks of matching RAM in every bank to no avail; I have a green light on the logic board, but still no chime or video. :( The PRAM battery is new - pulled from a working machine, so I know it's a good one - but it's also had no effect. For what it's worth, there is nothing attached to the board at the moment; it's just a bare board with a keyboard and monitor running to it.

IMG_1994.jpg

 

 

Thats for the lock on the front of the machine. Try plugging it in and see what happens. The key should be in the vertical position.

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8 hours ago, Sir Foxx said:

Thats for the lock on the front of the machine. Try plugging it in and see what happens. The key should be in the vertical position.

Same result, unfortunately; not sure why I had it disconnected in this image. However, I fear it may be dead dead now. I powered it up, noticed a burning smell, and then the PSU cut off a moment later. I looked under the board and noticed a couple of burnt pins on the bottom first socket for bank A of RAM. I'm assuming it's completely toast at this point, yeah? 

 

EDIT: for what it's worth, I didn't exactly expect this thing to work perfectly when I got it. I am a bit disappointed that this wound up happening, though. :(

 

IMG_1997.jpg

Edited by warmech
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9 hours ago, warmech said:

Same result, unfortunately; not sure why I had it disconnected in this image. However, I fear it may be dead dead now. I powered it up, noticed a burning smell, and then the PSU cut off a moment later. I looked under the board and noticed a couple of burnt pins on the bottom first socket for bank A of RAM. I'm assuming it's completely toast at this point, yeah? 

 

EDIT: for what it's worth, I didn't exactly expect this thing to work perfectly when I got it. I am a bit disappointed that this wound up happening, though. :(

 

IMG_1997.jpg

what do you have the motherboard sitting on?

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9 hours ago, Sir Foxx said:

what do you have the motherboard sitting on?

Plastic, which is what made the smoke/burning smell; there wasn't any visible metal anywhere nearby, which is what threw me for a loop. I just got back from running errands, so I'm going to eat dinner and have another look in a few.

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Well, went and checked - C155 is shorted, along with just about every other capacitor. The +5v rail is shorted to ground somewhere; I'm guessing that probably fried a few things.

 

Oh well, it will make a nice shelf piece.

Edited by warmech
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On a 30 pin SIMM pin 1 and pin 30 are 5V DC and that square pin that shorted is pin 1 on the socket. Pin 2 is /CAS.

 

Burning plastic turns to carbon which is conductive so clean the black goo off with alcohol and see if it is still shorting the 5 volt rail. If all those tantalum capacitors were shorted to ground I expect them to explode so its something else. The power supply should shut down on a direct short.

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8 hours ago, Unknown_K said:

On a 30 pin SIMM pin 1 and pin 30 are 5V DC and that square pin that shorted is pin 1 on the socket. Pin 2 is /CAS.

 

Burning plastic turns to carbon which is conductive so clean the black goo off with alcohol and see if it is still shorting the 5 volt rail. If all those tantalum capacitors were shorted to ground I expect them to explode so its something else. The power supply should shut down on a direct short.

Hey! We're back to square one, but at least it isn't as dead as I had assumed. Voltages look fine so far all over the place, but I'm still testing.

 

This thing doesn't need drives hooked up to boot to the [?] screen, does it? I know that's probably a dumb question, but this is an enormous, clunky, and (for me) somewhat rare piece of hardware, and I feel a bit out of my element just looking at it, lol.

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19 hours ago, warmech said:

I've tried four sticks of matching RAM in every bank to no avail; I have a green light on the logic board, but still no chime or video. :( The PRAM battery is new - pulled from a working machine, so I know it's a good one - but it's also had no effect. For what it's worth, there is nothing attached to the board at the moment; it's just a bare board with a keyboard and monitor running to it. 

FWIW, I had this issue with 4 matched RAM sticks that worked fine in a Q700 but gave exactly these symptoms in a 950.  Make sure the RAM is fast enough, and for preference test with RAM that's been shown to work in another Q950.

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Okay, so after some additional examination it is safe to say that the +5v rail is, indeed, shorted to ground somewhere. I got suspicious after testing for bad caps and, sure enough, the +5v pins on the logic board's PSU connector all show continuity with the GND pins. I've removed (and reinstalled) the power connector and found no issues underneath it, so it's not a problem there. The PSU is fine and outputs the correct voltages, so it's definitely local to the logic board... I just have no idea where.

 

As massive as this thing is, I don't even know where to begin looking for a short. Are there even schematics available for the 950? Even so, with that kind of a short, is this thing even salvageable?

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