Film-Tech Forum ARCHIVE: Doremi ShowVault Power Supplies

This is topic Doremi ShowVault Power Supplies in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Rick Cohen (Member # 6140) on 05-25-2017, 07:46 PM:

The ShowVault has a dual power supply. I recently had one start to go bad, and simply replaced them both just to be on the safe side. My question is, if one of the supplies is bad, is there an easy way to tell which power supply is the bad one? I was considering swapping one of the power supplies into another ShowVault, and observing to see if the problem migrated to the other ShowVault.

Before anyone asks, we are a drive-in, and only operate two shows a night, or 4-5 hours each day, and for part of our season we are weekends only. We shut down the servers and projectors every night, and have been doing so since March 2012. With five screens, we have not lost a hard drive yet, and this is the first time we have lost a power supply.

Our season is weekends only through March, April, and May. Full time from Memorial Day to Labor Day, then back to weekends only for September, October, and most of November.

Please do not start another debate about whether or not we should leave the servers running 24/7 during our season, we have been doing it this way for five full seasons, and are happy with the results.

Since we are a seasonal drive-in, and not running 5-6 showings each day, our replacement schedule for components such as power supplies, hard drives, fans, and coolant pumps is probably much longer than a typical indoor cinema.

Thank you for any and all feedback.

Posted by Marcel Birgelen (Member # 6801) on 05-25-2017, 08:22 PM:

How did the defective PSU manifest itself in the first place?

Often, failed PSUs indicate their failure with an amber LED instead of a green one on the failed PSU, but AFAIK the ShowVault only has green LEDs.

Posted by Rick Cohen (Member # 6140) on 05-25-2017, 08:56 PM:

The ShowVault wouldn't power on, or would power on only after repeated attempts to activate the switch. Replacing both power supplies solved the problem, even though it is likely that only one of them is actually bad.

Posted by Leo Enticknap (Member # 534) on 05-25-2017, 11:29 PM:

In that case, I'd guess that both of them must be NFG. The whole point of double redundant power supplies is so that if one fails completely, the server can continue to function on the remaining good one.

That having been said, maybe the BIOS initialization procedure pulls a surge of power (e.g. to test all the fans at full RPMs briefly) that requires more amps than one by itself can provide? If so, then that might cause a situation whereby the machine would continue to work if a PSU failed after the BIOS initialization process was complete, but would not be able to boot from cold (at least, not easily) on a single PSU.

If the pins of the output connector are large enough to put multimeter probes on without the risk of shorting anything, and you can find a circuit diagram to tell you which pins are which, you could measure the output DC voltage to see if it's what it's supposed to be. You could also open the top of one of the supplies to see if there are any obvious signs of trouble in there, e.g. a blown capacitor vent and goo all over the PCB.

If both the PSUs that came in the server from the factory were of the same model and batch, then it's not beyond the bounds of possibility that they both failed at around the same time. It could be that one went some time ago and you weren't aware of it, but it was only when the other started to die that you noticed symptoms.

Posted by Dave Macaulay (Member # 813) on 05-26-2017, 05:40 AM:

The monitor circuit only monitors the standby 5V supply so a PSU with failed main outputs will not cause the error beep. You can test if both work, though.
The 4U supplies are can overheat with the system off, when the standby supply is powered but the fan is stopped. The start button gets a flash from the drive LEDs and maybe a short beep then nothing for a second or two... then it tries the other PSU which usually works: then the fans start and cool down whatever was too hot to work.
Pull out one of the 2 power cords, or the 4U PSUs have a power switch you can turn off. Press the start switch... if it starts up with fans and a beeeeep pull the cord out again within a few seconds - before Linux begins booting. Then try with the other PSU.
Doremi servers can fail if power is cut while the SSD is active, so if it gets to the Linux boot crawl you should let it completely boot and then power it down normally to test the second PSU.
The "off" overheating/failing PSU issue happens after being off a long time, try the test first thing. Once the server's been running, the fans cool them down and you won't find any problem.

Posted by Mark Gulbrandsen (Member # 72) on 05-26-2017, 01:15 PM:

A bad power supply on a GDC gets you a fairly loud Sonalert tone and just look for which power supply's LED is out. The Sonalert tone can be disabled by a red square push button near the power supplies on the rear panel of the server.

Mark

Posted by Dave Macaulay (Member # 813) on 05-26-2017, 09:01 PM:

I haven't checked but GDC units likely work the same, monitoring SBY power and assuming the high current outputs are OK if that's on. It gets complicated and expensive to monitor all outputs and know when it's on vs standby.

Posted by Mark Gulbrandsen (Member # 72) on 05-27-2017, 06:44 PM:

I have not looked into that either. Only have had one supply failure in 7 years of GDC...

Mark

Posted by Steve Guttag (Member # 268) on 05-27-2017, 06:53 PM:

When the topic is about Doremi and the Showvault, why do you feel the need to provide unsolicited GDC information. It isn't that it isn't valuable to someone but it would be more appropriate in a GDC based thread.