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Mac Pro wont turn on - help

reebzor

reebzor

macrumors 6502a
Original poster
Jul 18, 2008
869
1
Philadelphia, PA
Long story short: Acquired Mac Pro, FedEx destoryed the case (Mac pro still worked), Bought a new case and swapped everything last night.

So I did the swap. Checked, and double checked that everything is plugged in. When I press the power button, nothing happens except I hear a noise coming from the Power Supply. Sounds like a click/discharge noise.

I've reset smc, done everything I can think of, but I still can't get the machine to come on. Anyone have any advice for me?

Much Appreciated.
 
reebzor said:
Long story short: Acquired Mac Pro, FedEx destoryed the case (Mac pro still worked), Bought a new case and swapped everything last night.

So I did the swap. Checked, and double checked that everything is plugged in. When I press the power button, nothing happens except I hear a noise coming from the Power Supply. Sounds like a click/discharge noise.

I've reset smc, done everything I can think of, but I still can't get the machine to come on. Anyone have any advice for me?

Much Appreciated.
Click to expand...

I had a similar issue recently. I bought an additional Mac Pro on craigslist ($1K for a fully loaded 2008 8-core with 16GB RAM!) and it was literally filled with dust. Caked. I went through 3 full cans of airduster.

It was working fine, but I took it apart completely to clean it and it wouldn't boot properly afterwards. The solution was disconnecting power AND removing the PRAM battery for a short period of time. I'm not sure what happened, or if this will help you, but this did it for mine.

If that doesn't do it, you'll need to turn it on and then press the diagnostic LED button. If you have a 2006-2008, you'll have to use a PLASTIC stick and poke(hold) the button between the memory slots; it's way back in there. Report which LEDs light up and I can tell you what the pattern means.
 
Ok, so I removed the PRAM battery and I have left it out. When I plug the Mac Pro in, it makes that same sound coming from the power supply.

What I noticed is that one of the Diag LEDs flashes for like a split second when I plug it in. It looks like its one of the CPU FAIL or OVERTEMP ones.

Now, I'm sure the CPU's are fine because the machine worked before and I didnt even remove the CPU's from the socket. I guess it's possible that thermal paste wasnt applied 100% correctly when I put the heatsinks back on, but would that really prevent the machine from turning on?

I dunno, I could take the heatsinks off and reapply the thermal paste, but is that even going to help?
 
reebzor said:
Ok, so I removed the PRAM battery and I have left it out. When I plug the Mac Pro in, it makes that same sound coming from the power supply.

What I noticed is that one of the Diag LEDs flashes for like a split second when I plug it in. It looks like its one of the CPU FAIL or OVERTEMP ones.

Now, I'm sure the CPU's are fine because the machine worked before and I didnt even remove the CPU's from the socket. I guess it's possible that thermal paste wasnt applied 100% correctly when I put the heatsinks back on, but would that really prevent the machine from turning on?

I dunno, I could take the heatsinks off and reapply the thermal paste, but is that even going to help?
Click to expand...

I should have noted that it is default behavior for some or all of the LEDs to flash briefly upon power on. If the CPU error or overtemp stay on, that's when you have an issue.

The other diagnostic LEDs will only light up when you hold the button. If you can hold the button and report which leds are lit and which color I could tell you what they mean.

If anything, you probably did it a favor by changing the thermal compound. I wouldn't worry about that. As someone else said, just make sure everything is connected properly and give it another go.
 
So I took everything apart again. Checked every connection, cleaned the CPU's and heatsinks, put some new Arctic Silver 5 on them, put everything back together -Still Nothing.

When I hold down the diag button, only the Trickle lights up. What does that mean?
 
reebzor said:
So I took everything apart again. Checked every connection, cleaned the CPU's and heatsinks, put some new Arctic Silver 5 on them, put everything back together -Still Nothing.

When I hold down the diag button, only the Trickle lights up. What does that mean?
Click to expand...

When you hold down that button LEDs 1, 6 and 7 should be on. 1 means the power supply is providing trickle power, like what would be required to maintain sleep mode, etc. 6 means that EFI has configured the GPU.

LED 7 would mean that the power supply is successfully powering all rails. If it's off, you either have a bad power supply, there was a short, or something was reconnected improperly. I would double (triple?) check that you have every power cable connected to where it is supposed to be. Usually, the computer won't even show trickle if the power supply is bad.

It sounds like something is preventing your power supply from switching to 'power on' mode; that signature 'click' that Mac Pros make when starting up or waking from sleep. Do you hear that click?
 
Ok, so now I must give even more information.

I believe the replacement case I bought was for a 2008 Mac Pro. I didn't realize this until I had received the case, but other than a little metal bracket in the optical tray area (which was easily removed) everything fit fine so I wasnt worried about it.

There are 4 cables coming out of the power supply (the original 2006 one), which in the 2006 case plug into a "backplane" type thing with 4 wires coming out of it. The new case has the 4 female connectors, but they were just kind of hanging free unlike the original case.

I think I plugged all of the power cables in the right order, but maybe they are different for this case? Everything fit fine and I figure there wouldn't be a difference what order the cables are in because they are all connected so they should all get power.

Could that be the issue?
 
reebzor said:
Ok, so now I must give even more information.

[...]
Could that be the issue?
Click to expand...

Absolutely.

They should all be different sizes and pin counts, but it is definitely possible that the configuration changed and something isn't going where it is supposed to. The harness should say JS1-4, and the power supply should say PS1-4; they would match up in a normal scenario.

Did you use the power harness that came with the 2008 case, or did you transfer over the one from your 2006 case?

Did you use the 'Front Panel Board' that came with the 2008 case, or did you transfer over the one from your 2006 case? It could be that if you used a 2008 FPB it isn't sending the correct Power On signal.
 
reebzor said:
Ok, so now I must give even more information.

I believe the replacement case I bought was for a 2008 Mac Pro.
Could that be the issue?
Click to expand...

Almost 100% it is. 2008 front panel has slightly different pinouts than 2006 one. So there could be a short.
Power On is the same, but in 2008 2 pins have 5V power for USB while in the 2006 they're not connected.
 
Yes I am using the front panel from the 2008, I'm not quite sure what you mean by "power harness" but I am pretty much using everything I can from the 2008 case.

Should I switch out the front panel, the harness, or both?
 
reebzor said:
Yes I am using the front panel from the 2008, I'm not quite sure what you mean by "power harness" but I am pretty much using everything I can from the 2008 case.

Should I switch out the front panel, the harness, or both?
Click to expand...

Switch it all out. Use as little as possible from the 2008 case (except cosmetic things like drive sleds, etc).

By power harness I mean the set of black cables that run from the power supply down to the various motherboard connectors.
 
Just a little update:

I was lazy and didnt feel like taking the thing entirely apart so I only swapped out the front panel. There was no change.

Tomorrow I will swap out the power harness and report back.

If anyone has any more suggestions of things I could do, I would appreciate it.
 
So I didn't realize replacing all of the power cables would be as much work as it is.

I checked all of the power connectors on the cables and all of the wires are in the same position for both cases. I don't understand why it would make a difference then which set of cables I use.

I am out of ideas for other ways to fix this though, because other than those cables, everything is exactly the same. Any second opinions?
 
So you swapped everything over but the cables (since they look to be exactly the same)? If so, why not just swap it all for completeness' sake?
 
So another interesting piece of information. It appears as though there are more risers for the Logicboard on the 2008 case than the 2006 case. My problem might be due to the logicboard grounding out on the case. Unfortunately, this could have resulted in my logicboard frying.

Ugh, this is just getting worse and worse
 
So I just put everything back in the 2006 case. The case is damaged, but everything works fine. I'll just deal with it.

So just for the record, a 2006 Mac Pro can not be used in a 2008 case.
 
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