Slashdot Mirror
PC Not Booting Until a Different Phase is Used?
2by4 asks: "I run at IT Dept for a small firm, our network room houses production &
development servers. Some machines are plugged straight into a strip with
no UPS. Here is the Mystery Problem: When the power glitches, the strip
machines go down, and some of these machine WILL NOT come up again until I switch
them to a new outlet. Once this happens, I can put them back on the original outlet
and they will work. Unplugging & replugging on same outlet is not enough. I have seen this on at least 5 machines so far, with independent confirmation. We can narrow the 'fix' to plugging into an outlet of a different phase (there are 3 separate 120v phases powering the room). The symptoms vary from no powerup, to frozen at the BIOS (depends on motherboard make), etc, but consistently, switching to a new phase fixes them. I tried the 'unplug-wait-&-replug' cycle, to no avail. Using a new outlet w/ a different phase is the only solution. Any theories? I assume the new phase is causing something to 'reset', but what? I can provide more details, but I am wondering if anyone has seen this before? I am completely and absolutely stumped. Our power is healthy, lightly loaded, evenly distributed and the power strips are new. I know I should have at least a simple UPS, but this mystery is causing me to lose sleep."
Obviously, I mean that you should do this with the plug UNPLUGGED.
Try resetting the circuit breaker on your "strips".
--
Twoflower
You mention when your power 'glitches'...brownout or blackout or spike?
We are a light industrial building in a heavy industrial park, and I swear the power goes glitchy 2-3 times per year.
We'll get brownout and blackouts, and when the power comes back it SEEMS like it's on, but only 2 of the 3 phases of the A/C actually comes up, meaning (depending on how it's wired at the *circuit box*) some circuits are dead, some are full, and some are semi-brownout (our flourescent ballasts LOVE that half-state.....not).
That third phase sometimes doesn't come back up for hours.
I have no idea if this is of any help, that electrical stuff is arcana to me, I'm just reporting what we've discovered.
-Styopa
I think starting the article with "We have since gone out and bought some fairly inexpensive UPS's to eliminate this problem but nonetheless the phase detection has piqued my curiosity
....... Thus ends my attempt at wit or whatever
More likely a competent electrician, if some of the outlets are fine and some aren't.
LOAD "SIG",8,1
I actually worked on a system where printer interfaces were burning up because an electrician had reversed neutral and ground in the outlet where the printer was plugged in. There was enough of a difference between neutral and ground to damage the interface of the computer.
For every problem there is a solution that is simple, obvious and wrong.
This sounds like it could be a ground problem. I'd check (if you have the capability) the hot-to-ground and the hot-to-neutral with an oscilliscope on the effected outlet. Barring that you can check it with a multimeter, you may find that the neutral or the ground is inductively coupled to a hot phase.
Some other things to check:
The continuity between the outlet and the electrical box (all three wires).
That your grounding rod is correct for the type of soil in you area.
A different power supply.
Also, like a previous poster noted, try shorting the input to the power supply (when it is unplugged), that may give you a temporary fix.
- you may well have a grounding problem either on the strip or the outlet that the strip is plugged into.
- when a computer is in the "won't work on this strip" state: unplug it and ground each of the 3 terminals momentarily. You can do this by simply touching all three prongs to the metal face plate of a switch or plug. (this is similar to the suggestion that someone gave about shorting out the prongs with a screwdriver but better). Then try the computer. If this works then you may have a floating ground on the strip or somehow voltage is getting induced onto the ground.
- you can buy a simple tester to test the wiring on a duplex plug. Home Depot usually caries them for less then 10 bucks. The plug into a 3 prong outlet and have 3 lights on them (2 orange and a red if I recall correctly). Depending on which lights light up tells you about the wiring and suggests what the problem is. I have even found high resistant neutrals and other such strange wiring problems with it.
Of course once you have tried this (or not) and have a better idea where/what the problem is, it is time to call a qualified electrician.Merlin.
Have an electrician come in and do some wiring checks and fixes. You have a combination of two problems causing you to see this.
1: You have poor to non-existent grounds on one or more of the phases. This can be tested for by the electrician.
2: The HOT and Neutrals are swapped around and generally this isn't an issue except that *modern* power supplies are getting cheaper and cheaper and this usually means cutting out *some* parts like full-wave bridges for half-wave diode sets, and similar tricks. This then makes the circuit more effected by incoming AC and it's phase against ground or what little there is of it. (hence the reason for #1) There more than likely is a potential difference between the neutral and ground that is excessive and this is causing a cap-start circuit to ignite the switching and hence, a dead PS.
Cheers;
All content in this message is copyright (c) 2008. All rights reserved. RIAA is prohibited here.
I've experienced similar problems in the past, due to current leakage. Especially with different phases, but also commonly with poorly grounded devices or devices which had peripherals or cables running close to sources of high levels of common mode noise.
Most commonly, when plugged into a peripheral or another device which is separately powered or grounded.
What was happening was small amounts of current leaking in through peripheral components was affecting the power supply... Usually to stop them starting up. ie, hit the power button, no start, no lights. The leakage was in the micro-amps region, but was enough to leak back through the motherboards into the power supply, and cause a false fault condition reading on start up, and the PSU would shut down before it got started.
The solution? In one instance, I decoupled the power rails. In another, better grounding. Another? Changed phase. The best solution was usually to find a better power supply that wasn't affected, but was not always possible.
Often in these circumstances you can feel the current leakage, as it's often at high voltage but very low amps. Sometimes it feels like a slight tickle when you touch rivets on the case.
Additionally, I've also encountered similar problems due to engineering faults, where a high impedance section of the circuit was acting like a radio antenna and was getting enough "reception" of a local signal (any strong electromagnetic radiation source) and causing a fault condition on power up that was not present during normal operations (when the applied signal was significantly stronger than the picked up signal).
Solutions there include EMF shielding and redesigning the circuits.
Problems like this are difficult to diagnose, as they are not always obvious, and there is very little you can do to test or troubleshoot directly. Often it involves experience and a little lucky guesswork.
GrpA
Enjoy science fiction? "Turing Evolved" - AI, Mecha, Androids and rail-gun battles. What more could you want?
There are two ways this can happen:
Note that this can be induced in otherwise properly bonded circuits by the use of daisy-chained power strips/bars. It is the act of plugging in a (typically high-power) item on the end of the line (so the draw through the whole line is high) and connecting it via a signal cable (Ethernet, serial, USB, etc.) to something plugged closer to the junction box (electrically) that then ends up routing some of the ground current through the low-voltage signal line.
In general, the cure is to return to the bonded-circuit of yesterday designated by the orange plugs where they've been installed. These consist of a single plug per circuit (never more than one!) where ground is bonded to neutral at the connection box so there is no possibility that there may be a voltage drop due to current between individual recepticals.
We seem to have gotten away from the specification and use of these (more expensive to install) power recepticals. I for one continue to specify them for most commercial installations and have yet to see any of the kinds of things mentioned here when they have been properly installed and used.
The worst case I saw of this was in an office that was long and skinny in a brand new building (they were the top floor) with retail below. The office went in first, and the retail later proved to include a dry-cleaner that used quite a bit of power off two phases of the 3.
A Unix computer in the center of the long office fed dumb terminals the length of both directions. The reception area was the farthest out - about 100' by wire - RS232 shield.
The terminal at reception kept doing wierd things: hanging, mystery characters, and in fact died - 3 times! Lights on but nobody home!
It turned out the serial interface was dieing - due to about 5 volts between ground and neutral which was pulling current through the cable's cladding and buring out the chip. The electrician poh-poh'd it saying "5 volts on a 120volt line was nothing to worry about" but in fact it was 5 volts on a 12 volt circuit and carried current in what should have been a voltage (high impedance) system. No wonder the interfaces were flaky and buring out.
Replacing the power plugs with "home-run" single bonded ones fixed the problem.
Been there, done that, paid for the T-shirt
and didn't get it