Burning Furman!

[amino]

I have some Furman Power Conditioners in the studio. I know they don't that much, but they do provide some security. I guess.

Today I ran into all sorts of problems. When I turned on one of my Furmans (a PL-PLUS) a fuse in the house blew. I tried to locate the problem and three fuses later it started to smell pretty weird. I then realized that the problem seemed to be the Furman itself. When I opened it up I found two burnt capacitors (see in next post).

How did this happen? I only had two machines connected to it at the time and they seem to work fine. I use these machines to avoid these kind of problems, not to create them...

[amino]

Pics...

[tINY]

Well, it looks like the MOV was doing something in your case... which is why it failed.

You should replace the Furman with a 2-fer and hook up a scope to see what this thing was reacting to.




-tINY

[amino]

Thanks. Unfortunately I don't have access to a scope at the moment.

I might add that we have a storm just outside the window at the moment. Thousands of households 10-30 miles away from here have lost electricity. I haven't noticed anything here yet, no flashy lights or anything like that. However, it doesn't mean that we haven't had some nasty transients...

[amino]

I might add one thing as well...we have 230V here in Sweden, but this is a 110V power conditioner who gets power directly from a decent stepdown transformer.

[tINY]

You might want to check the output voltage of the transformer (and polarity - neutral tied to ground).

I had a MOV fail in France being fed by a transformer and suspected the 50Hz, but it's hard to say...




-tINY

[ktf]

I've seen MOV's go bad for no apparent reason and when replaced everything is fine.

[Wavebourn]

They are not capacitors; they are varistors that protect device against an overvoltage. I can't read what is written on them; it may be a clue: either they were rated for too small voltage, or you had too high voltage in your outlets. What is bad, they were not connected after fuses so in-house fuses were used. They died protecting your computers.

More info: http://www.vishay.com/docs/29081/23815925.pdf

[triez]

It may just be that the MOV's were just doing their job, ie: going short circuit and blowing the fuse. This is what they are meant to do if they get too high a transient, so in your case the MOV's probably sacrificed themselves to shunt a power surge back the way it came. I have seen a Furman fail spectacularly, it looked like a strobe went off inside, and bright light came out of every hole and gap in the case.

[amino]

Of course it's a varistor. My bad.

The MOV is rated S20K130. The voltage transformer delivers 115-117V in my house and can be found at MW USA - UK Voltage Converter 300w (MW2P300) - £22.67 : B.G Stores. The actual load is less than 50W.

I can understand that the MOV's are doing their job, but is the Furman really doing its job? Is it supposed to break itself when protecting other equipment? I do find it a bit weird that the household fuse blew and not the one in the Furman or the one in the voltage transformer, and the rest of the house didn't have any problems. Also...it all happened just fractions of seconds after I turned on the Furman. It sounds weird if there was a nasty transient exactly at that moment.

Hmm...I'm not sure and this doesn't make sense to me...but if I try to recall exactly what happened the first time the fuse blew I actually think that the power switch on the voltage transformer was off!? I remember because I turned it off the day before and I've never done that before in the current configuration. I turned on the Furman and got a quick flash but then everything went off. The next time I tried I turned on the voltage transformer first. I don't notice anything strange now when I turn it on or off though, and I mean...it's just a transformer, right? Maybe I should open it up...

[ulysses]

Originally Posted by amino

Is it supposed to break itself when protecting other equipment?

Yes. The MOV is a sacrificial part. Most surge arrestors include documentation that says you're supposed to replace them after they've been through an event like that. The nicer ones have lights on them to tell you if they've done their job and need to be replaced.

But I was under the impression that after they've been destroyed by shunting away a large transient, they're supposed to go open and not do anything at all, including not protect against future transients. I suspect that yours shorting out may be somewhat unusual.

I don't think any of us remote theorists can say whether the power switch on your step-down transformer had anything to do with it, but it's certainly something to keep an eye on in the future.

[tINY]

I have seen several MOV's that shorted on failure - and I read that this is the common mode.

The transorbs tend to fail open (or so I read), but they are more expensive.




-tINY

[triez]

Originally Posted by tINY

I have seen several MOV's that shorted on failure - and I read that this is the common mode.

The transorbs tend to fail open (or so I read), but they are more expensive.




-tINY

They go low resistance on a transient to shunt it, if the transient is too big they go really low resistance and then blow up, normally they are then O/C, but sometimes they can be left short circuit, perhaps if the surge fused the metallic components together. They can be pretty spectacular when they fritz out.

[Wavebourn]

Originally Posted by amino

The MOV is rated S20K130. The voltage transformer delivers 115-117V in my house and can be found at

It can dissipate 0.1W without self - destruction. 205V applied cause 1 mA current. When applied 340 V it shorts sustaining up to 100 Amper.

Transformer can cause high voltage peak when disconnected.

[amino]

Thanks a lot for all your replies!

Originally Posted by Wavebourn

Transformer can cause high voltage peak when disconnected.

This sounds very interesting. Can anyone explain when and why this phenomena can occur?

The voltage transformer is not supposed to be opened up, so I will probably break the enclosure if I do. I don't know if I want to use it anymore though...

[Wavebourn]

Originally Posted by amino

Thanks a lot for all your replies!


This sounds very interesting. Can anyone explain when and why this phenomena can occur?

The voltage transformer is not supposed to be opened up, so I will probably break the enclosure if I do. I don't know if I want to use it anymore though...

Speaking "on fingers", a capacitor saves a voltage, but a coil saves a current so when a coil that conducts a current is disconnected it tries to increase a voltage in order to restore the same current, but since resistance become abruptly high it generates correspondingly high voltage. Ignition coils in cars use this phenomenon to generate sparks.

[AMIEL]

I never liked the Fuema Power Conditioners they burned my Tannoy 800A and that was $700 to make them new!!

[Jay-]

A friend of mine is desperate to buy my older Furman PL Plus with lights.
He offered $120. Im international and have sold all my equipment preparing for a move. This I think is a good price, but I do have my M-audio Projectmix attached for recording an acoustic guitar.

Question is, does the furman really do anything?
I live in a very bad power area, its reading 130v now.
Im buying a new Kurzweil PC3 in a few months and thought hell id get the Furman PL Plus II for near what im selling this one for.

Do they really work? Often the transformers out side explode.
Then again my extensive home entertainment center is running of those $10 power strips and im told a good jolt nothing is going to protect you.

The fast cash of $120 would really be nice twords the PL PLUS II!
Or do I risk gear death?

At the moment im using the furman and a power surge.
Often I suspect the furman is nothing more then a 1U blanking plate with 8 plugs and cool light. My friend is getting actual line noise but I don't record at this location now.

Do they really protect or just condition?

Peace.

jay.

[AMIEL]

If you have 130V ...be ready to fry any of your gear soon!
What you need is a Voltage Regulator and that is much more expensive than $120!

If the voltage read that number your surge protector should be off already and blocking power!

Believe me a good voltage regulator and good power conditioning will protect ypur invest me and save you time , money and frustration at the end!

[Jay-]

its been at 130v for 5 years. Sometimes the furman just blinks with all the LED lights in red. I called furman and they were unable to tell me what to do.
Well I sold almost all my gear but the mixer and the PC daw. Not even speakers any more. Small home studio.

Just acoustic guitars now, but I am curious if the furman "protection" is real or just cleans the signal, lol... its really kind of snake oil in a way.. although I do like furman products.

They remove pops and clicks from the signal or do they save gear from catastrophic power surges?

Thanks, electricity noob..

[Phil Cibley]

Originally Posted by amino

How did this happen?

I've found that the On/Off switches in power strips/conditioners to be a weak
link across several brands and price points. I've had to replace too many over
the years.

[zak7]

Me instead to allow the Furman burn your gear I will burn the Furman first!!

[ulysses]

If you're in the United States and your power line is feeding you 130V, I suggest you call your electric company and complain. It may be a long and irritating process, but I think you should be able to get them to come out and fix it. There's almost nothing you could do to the wiring inside your house that would cause the voltage to go up, so they must be feeding you a high voltage. I think 117V is nominal, and 10% over that would be 128.7. 130V is clearly "out of spec" and should be dealt with. I assume they'd send somebody out to move the feed to a different tap on the transformer. If you can get your neighbors to also complain, they might be more likely to respond. I don't know for sure, but I would expect some sort of regulatory oversight body to take your side on this matter.

[tINY]

Line voltages have been creeping up for the past 3 decades. Some people will tell you it's a conspiracy - the power companies raise the voltage, deliver a littel more power and charge quite a bit more in rates because of how the meter is calibrated.




-tINY

[Wavebourn]

Originally Posted by zak7

Me instead to allow the Furman burn your gear I will burn the Furman first!!

It can't burn a gear. It can sacrifice own life only.