Power Conditioner Flickering Cause? Help! (I don't want to start a fire!)

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LmnLm3

New member
I've been having problems with my old monitors (M-Audio BX5a Deluxe) and new ones (Yamaha HS5) are on their way from Sweetwater. Before I plug them in, I'd like to get to the bottom of this... in case there's a problem with my Furman M-8x2

One of my BX5s died a slow death over many years, so I've been mixing in mono. Cool. The remaining speaker has been developing self-noise hiss more and more over the past few months. Today, I heard crackling, and when I looked over I saw that my monitor screen was off (it's also plugged into the same power conditioner.). I also have plugged into the same conditioner a Saffire Pro 40 and an Avid Eleven Rack. The 11R was off at the time, and I didn't hear the signature "click" of the Saffire turning back on and reconnecting, so I assume it didn't lose power long enough to reboot.

I unplugged the BX5a and put it on the floor for now, because I'm worried about my other gear. Could it be from the cold weather? Local power substation had work done today as well... And when I reached to turn the monitor off (before unplugging it), I got a low voltage (but higher than normal current) static shock on my hand. It felt mild, but lasted longer, so I'm guessing it was higher current than a normal winter shock, but it was definitely lower voltage than I'm used to feeling in my house... (though maybe it is mitigated when something is grounded in a good power conditioner? I don't know enough about all this!)

Is this something that a failing power supply in a monitor could cause? Or is this more likely a problem with my power conditioner? It might be within 2 years from Sweetwater... How do I test this kind of thing? I'm fine screwing with pedals and a soldering iron, but I'm not the type to mess around with mains 120v outlets without flipping the breaker first...
 
First thing - it wasn't a static shock. Static is a high voltage, low current source, which discharges through to ground via you. The high voltage means even a little spark can jump. However - it's one off. Like wiping your feet on a man-made carpet, then touching something grounded like a radiator. A sudden discharge as your hand makes contact, but a second touch produces zero. That's static and could be many thousand volts. The almost zero current means that while annoying and a pin prick pain - it's gone, and safe.

A constant tingling is bad. It means continuous current, and if the current is high enough, your muscles start to jiggle - at 50 or 60Hz. It is always a fault. The current is getting to ground potential through you. First thing is a simple multi-meter. Stick it on the AC volts scale and put one end on something grounded, and prod the other onto your kit. With your power conditioner being a possible culprit, I'd start with that - disconnected from everything, and sitting on the floor where you can get to it. I assume it's a 3 conductor grounded device? Plug it in and then check with the multimeter. The tests are simple, and if you use the insulated probes, quite safe. In the UK all our outlets are shielded - little covers stop fingers or objects getting in - but in the US, these openings are just 'hole's. Can you identify which is which - ground, live and neutral? Live to neutral should read your full mains voltage (using the AC setting) - usually 110-120V, so if it says 115.5V that's fine. You should have nearly the same reading between live and ground, and from neutral to ground expect 0V, but be happy with just a few volts being present (It's to do with your mains intake type and the ground connection - in many homes nowadays, the neutral cable is bonded to ground - so neutral and ground potential will be very close. In big properties and certainly large factory spaces, cables are longer, so neutral can drift a little, but only by a few volts.

Another test is to find a decent ground in the room - possible a radiator if you have metal pipes, and test between that and the live, then again between the radiator and the ground in the conditioner. The conditioner ground needs to be the real ground - because all the metalwork in your equipment will be connected to it!

Touching the monitor and getting a continuous shock is a concern. Is the monitor grounded or floating, with just a two core mains cable? Is the switch metal? They're normally plastic? Your multimeter can be used with one end on real ground (from a reliable source) and the other end used to touch metallic parts of each item of gear, that is plugged in and powered up. You really shouldn't see voltage anywhere. If you do, something is wrong. The most likely culprits are switch mode power supplies - we see them everywhere, and a fault could put volts onto the chassis - which if floating means the ground connection of audio or video cables will also be live. If you plug these into something grounded, the fault current transfers to ground through their ground cable - making the system safe, but prone to shocks if one item (doing the grounding) fails or is removed. I had this myself. Years before, I ran out of cables, and had in the rack and unused, a Tascam cassette recorder. It had a loop-through, in to out - so was being used to get audio to the destination. It sat like that for years, and when I eventually pulled everything out and started again - I got a shock and discovered the power supply to one of the units in the rack had failed, and it was sticking half the mains voltage 120V, onto the audio ground, but the faithful old tascam had been grounding it for an unknown time. removing the Tascam gave me the shock. The current (as I'm alive) was thankfully quite small, so it was a bad tingle, not a heart stopper!

If you pull your system apart, unit by unit, you should with just a cheap meter, be able to systematically check each piece and work out where the problem is.

Clearly you need some common sense and basic physics - but the meter will show you where the problem is. It's not quick process, of course - but I bet the problem is somewhere other than the conditioner.

I loked at the spec for the conditioner and it's a bit lacking in detail - it seems to offer reduction in RF - 200KHz and above - so probably a chunky ferrite on the conductors, and as for spikes - probably just the usual voltage sensitive components. It's main feature is really central grounding of everything attached to it - a star grounding system in electrical parlance. I doubt it is the cause, but it does present a good method of grounding and residual current being introduced elsewhere - so my guess is your problem could be that monitor - I'd start there first. I doubt it had anything to do with the speaker amps dying - not really the kind of problem it's capable of causing.
 
rob aylestone said:
First thing - it wasn't a static shock. Static is a high voltage, low current source, which discharges through to ground via you. The high voltage means even a little spark can jump. However - it's one off. Like wiping your feet on a man-made carpet, then touching something grounded like a radiator. A sudden discharge as your hand makes contact, but a second touch produces zero. That's static and could be many thousand volts. The almost zero current means that while annoying and a pin prick pain - it's gone, and safe.

A constant tingling is bad.
Click to expand...

Thanks for your detailed reply! I should have been more detailed in my original post, though. It was not a constant current - I've felt that before from playing a bass amp in someone's basement that didn't have any grounding, basically 2-prong but even the neutral was lazy. It really got anyone who was barefoot. Fun times...

Anyway, when I say this lasted longer, I mean instead of it being 0.5ms like a normal static shock, it was more like 9ms (I'm making up numbers, but you get the idea). It was one and done, and happened from touching the back (painted plastic), but from what I know of these monitors (because of the one I took apart), it's not a very well grounded design imo.

rob aylestone said:
If you pull your system apart, unit by unit, you should with just a cheap meter, be able to systematically check each piece and work out where the problem is.

[...]

my guess is your problem could be that monitor - I'd start there first. I doubt it had anything to do with the speaker amps dying - not really the kind of problem it's capable of causing.
Click to expand...

I might do this anyway, with the meter I have. Doesn't sound too difficult, and better safe than sorry. That said, when you say "monitor" do you mean the video or audio monitor? I've never had a problem w the video monitor flickering out, but I have had issues with the audio monitors so my instinct is to blame them... I'm less concerned about the shock at this point, as it's been very dry and about 4ºF(-16ºC) outside last night so lots of space heaters and been getting static shocks in general around the house, it just felt a little different than all the other shocks I've been getting lately... Moreover, the whole thing acted funky before I touched it, with speaker snap-crackle and pop before the video monitor power cycled. I guess it could have been a fluctuation in mains voltage, though? Been having a bit of that with the dining room lights this month, but it's never before affected anything in my studio ¯\_(ツ)_/¯
 
One of the problems with power conditioners is that they use capacitors to filter out RF and often in a bad way where two caps are put in series across Live and Neutral and the centre point taken to earth. (you will find this configuration in MW oven supply) . Not a problem SO LONG AS THE EARTH IS REALLY LOW RESISTANCE. Any impedance twixt conditioner earth and the equipment it feeds means the earth/ground is 'sitting' on a voltage produce by the current in the capacitors.

My bet is that mains outlet feeding the conditioner has higher than it should be resistance. Is that outlet far from the incoming supply? (we call them 'Consumer Units' ) .

Sorry if Rob covered this but try the meter from and earth socket on the conditioner and a really solid, known good earth such as where the cold water comes into the house. If that shows a few volts at 60Hz then consider running a heavy earth cable TO said pipe! Mind you!! I have NO idea of American electrical 'Code' so make sure anything you do meets it.

Dave.
 
LmnLm3 said:
Been having a bit of that with the dining room lights this month, but it's never before affected anything in my studio ¯\_(ツ)_/¯
Click to expand...

Based on what you said in your first post...and this....it sounds to me like you are having broader electrical issues than just the speaker monitors or your studio power conditioner.

First thing I would do is check the voltage at any of your house outlets with a DVM. It's not complicated and takes just a little bit of effort and safety...you just stick the two probes into the outlet, and read the voltage. If it's way low or way high...you've got a problem, and you should call the electric company.

If that's already outside of your comfort zone...then just call the electric company and tell them you are having electrical flickering and voltage drops, etc.
They will send someone out to at least check your outside power source...they don't do inside the house. You might even ask them to put a 24-48 hour monitor on the source to see if it fluctuates over time, and by how much.
Sometimes if they are working in the area, they will already know what's going on, and it might be just a question of them finishing their work, and then everything is back to normal.
If all that checks out OK...then you might want to call an electrician to check the inside of the house. You could have lose wiring, bad grounds, who knows what (how old is the house?).

That said...maybe your speaker monitors are just shot, and something that obviously was going bad over time, since you already lost one.
 
Good advice - the temperature thing alone puts me at a disadvantage. Here in the UK we call -1 (31F) freezing, and lots of minus numbers makes us scratch our heads. I used to be a regular skier, and seeing electrical cables with huge Icicles used to make me wonder about US and European snowy electrics!

On a purely practical point off view - static should not be considered 'normal'. Usually un-grounded items can accumulate charge, but like Dave said, anything other than an instantaneous discharge is a fault, and I agree - capacitors somewhere have to be involved. Poor grounding somewhere that has perhaps changed is letting the problem be detected, when before it just leaked away to ground - now it does it through you. If your power company can check the state at the incoming point, you can then at least see if the supply voltage is compromised outside - and they can fix it. If they say it's fine, then flickering lights are a sure sign something is wrong, and your audio kit just manifests it differently - clicks pops, fizzing noises. Oddly, computers are the most prone devices to give up if the mains supply has glitches - but you've not mentioned this.

Based on everything - I suspect a more general problem in the house wiring somewhere, and finding it will be tricky, so perhaps the safest thing is to call in an expert - but I would do some basic testing yourself first - you might be able to find it?
 
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