My Sun Ultra 5 or Ultra 10 only powers on if I don’t have any cards in the PCI slots.

This tutorial came about as a result of an order we filled for an client. The client ordered nine Sun Ultra 5 Desktops. The order called for all the machines to be identically configured, except that seven of them needed a QuadFast Ethernet PCI Card and a PGX32 Video Card and the other two needed a QuadFast Ethernet PCI Card and a Single-Ended SCSI/Ethernet PCI Combo Card.

Once the hardware had been configured to spec, the techs powered on the machines to install Solaris and run some tests. They found that the two machines that had the “alternate” config seemed to power on, as evidenced by the fans spinning, but they would not give any kind of video output.

After doing all the usual troubleshooting steps (checking that the CPU, RAM and all connectors were properly seated, they tried removing one of the cards [the QFE card] and powering the machine on. That worked, so the fault seemed to lie with the card. To test this theory, they took a card from a working machine and put it into this Ultra 5. No luck. The machine would not power on.

FedEx would be coming soon, so I was called to the warehouse to decide if we would ship the order minus the two non-working machines or hold the order and ship complete when the problem was resolved. I decided to look at the machines myself. The techs told me what they had tried, but not having been there (and knowing that you never trust what someone tells you without seeing it with your own eyes), I wanted to see it for myself.

So I went through the same steps (put in the first QFE, power on, no result. Remove that QFE, put the next one in, power on. No result) That’s when one of the techs said the magic words: “It’s weird. It’s almost like the machine isn’t getting enough power to boot up. Like if you feel the fans, they’re blowing very softly.” Instantly, I knew what was wrong.

Most Sun hardware comes equipped with what is called “auto-switching” power supplies. This means that you can plug it into 110v or 220v and the power supply will automatically detect the voltage and adjust to work with that voltage. The thing is that there are some Sun machines that do not have auto-switching power supplies. The 2 machines that immediately come to mind are the Sun Ultra 5 and the Sun Ultra 10.

So what is the alternative to an auto-switching power supply? Well, I don’t know what it’s called. But instead of automatically detecting the voltage that you’re plugging it into, it requires you to manually tell it what voltage you’re plugging it into by flipping a switch on the back.

It turns out that the power supplies on these particular Ultra 5‘s were set to 220v. I’m no electrician, but I guess that if the power supply is expecting 220v and you only plug in 120v, the machine will be a little “under powered”. . . as evidenced by the fact that the machine would power on without the QFE card plugged in, but would “never completely” power on if the QFE card was plugged in. I guess that additional device was “the straw that broke the camel’s back” in terms of the power requirement.

So what did we do? Use a flathead screwdriver to flip the switch to the 120v position, put the QFE card back in and EUREKA! The machine worked exactly as expected.

Throughout my years of working on Sun hardware, I’ve seen this same problem manifest itself in several different ways. Once, a customer told me that his Ultra 5 would power on and go part of the way through POST, but would reboot all by itself. After trying various things with him, he reported back to me that he discovered the source of the problem — and it was the 220v setting on the power supply.

So if you’re experiencing any weird behavior with any of the machines mentioned above, it might behoove you to check the voltage selector switch on the power supply. I’ve also noticed that some of these machines will appear to work just fine when plugged into 120v current while the switch is set to 220v — except that the light near the power switch on the front will not light up.

UPDATE, Sept 21, 2009

In the last couple of months I came to find out that towards the end of their production life, Sun introduced some Ultra 5 and Ultra 10 models with auto-switching power supplies. These are VERY few and far between, but it basically means that there are some Ultra 5/10 systems that will not have a switch on the back for voltage selection.


Oh, and one final thing: You might be wondering what happens if you do the opposite of what I described above — what if you set the power supply to expect 120v, but plug it into a 220v power source. Well, I’ve had customers do that also — and the result is usually a loud POP and a whole lot of smoke! (which, if you’re in a data center with a fire suppression system, can get very interesting) BE CAREFUL – and always check the power supplies on your machines if they’re not auto-switching.

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