"Unsteady" wall voltages

Discussion in 'Shock Brother's DIY Amps' started by eslover, Jun 7, 2021.

  1. eslover

    eslover Tele-Meister

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    When I bought my townhome in Ellicott City I was told that the property lies on the edge of the power grid and, consequently, we are prone to brown outs. I've been living here now for 17 years and we've had our share but nothing to too unusual - every hard storm we can expect a flicker or two and one or twice during the heat of summer.

    I am just now finding out that my wall voltage is quite unsteady. On separate occasions I get anywhere from 120 to 128 (probably higher and lower still!). I've never paid much attention to this until recently as I have been trying to determine the correct no-load plate voltages on a amp build. Sometimes the plates will read 250-255vdc, then later in the day I get 268-270vdc...and I scratch my head. Well, its because the wall voltage has darn near shot up 8 volts!

    How stable are the wall voltages where you live?

    I would think a variac would be somewhat useless to stablize the wall as the variac will see these changes, too. Maybe I'm wrong here, but the cheap-ola "red" variac I have will move with the wall.

    Do any of you try to stabilize your wall voltage? Maybe use a conditioner or something?
    I'd really like to know. This is going to drive me crazy!
     
  2. magicfingers99

    magicfingers99 Friend of Leo's

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    a good ups (sine -wave) can filter your power and raise low voltage situations. think of it as a buffer, the batteries condition your power to clean it up and raise the voltage back to standard.

    they are available in many capacities, as the Amp-hour rating rises, so does the price. If you are only using it for power conditioning you can get by with a small capacity, just make sure it supplies true sine wave power.

    I don't use one at home, but l help source them for medical facilities.
     
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  3. PCollen

    PCollen Friend of Leo's

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    My wall voltages fluctuates between 120 and 123 VAC and I don't worry about it. But what you are seeing I would worry about. You may need something like this:

    https://www.bhphotovideo.com/c/product/1226864 REG/furman_spr_20i_stable_power_ac_voltage.html
     
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  4. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    This is why the old Fender schematics say "voltages shown + or -20%" -- there isn't ONE correct voltage for these things, there's a wide range of acceptable values because wall voltages vary, tubes vary, transformers vary, resistors vary, etc.

    You just have to lighten up and determine whether your amp is running in a healthy zone or not. If you're going to encounter excessive wall voltages a lot, consider building a voltage-dropping adaptor like this: http://www.geofex.com/article_folders/vintvolt/vintvolt.htm
     
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  5. Dan R

    Dan R Poster Extraordinaire

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    Spurious voltage is a problem just about everywhere. The best solution is a dedicated 20 amp circuit from your electrical box. I had this done at my former house years ago. However, this may not be practical for all instances. I would think a variac transformer would be the next best thing.
     
    Last edited: Jun 7, 2021
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  6. David Barnett

    David Barnett Doctor of Teleocity Ad Free Member

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    A few years ago I was seeing some wild swings. I'd see my AC get up to 135V, with a corresponding drop into the high 90s in the other room. Highest I ever saw was one Saturday afternoon when it got up to 146V (and ~80-ish in the bathroom). I complained to the power company, I thought the center tap on the high tension transformer wasn't bonded to earth. They claimed nothing was wrong, but next time we had a thunderstorm the breaker on the utility pole blew, and when the utility crew showed up to reset it, they replaced the transformer.

    It's been fine ever since, just the usual normal 119-125V fluctuations.

    I guess my point to the OP is to check - when your voltage gets over 128 in one part of the house, see if there's a corresponding drop on the other phase?
     
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  7. Speedy454

    Speedy454 Tele-Holic

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    A variac will not help much if at all. They are a variable Auto Transformer and will step down the voltage proportionately. There is no regulation built into them.

    Magicfingers99 is absolutely correct. A true On Line UPS is the only way to correct a widely fluctuating line voltage.

    The cheap UPS units are not a true On Line UPS and probably will not resolve this. They are designed to provide a semi sine wave or even a square wave after the line voltage drops out completely.

    A true On Line UPS takes the line voltage, converts it to DC, then converts the DC to a well regulated AC. Most have a battery array built into that DC buss to keep the AC output even during brown outs and black outs.

    These are what get installed in server racks and for other critical need equipment. They are available from a number of sources, and small ones can run a few hundred bucks.

    I work in the medical electronics field as well. We put big 150KVA units on our Cat Scans, MRI systems and Cardiac Cath labs. Those units put out 480V 3 phase at about 100A for 20 to 30 min. during a complete power failure.

    As a service engineer, I like the fact that when we install these with a new imaging system, reliability goes through the roof. They isolate the imaging equipment from 100% of the sags, surges, transients, brown outs and so on.

    Unfortunately, this is an option for our customers. Most don't want to spend the additional $$$ even though it will actually increase their patient throughput by significantly reducing their system down time.

    I have performed hundreds of power surveys in Missouri and Illinois ranging from 7 days to 30 days in duration. I think only 2 or 3 actually passed meeting all our specifications for voltage, frequency and line disturbances.

    This was not a sales pitch, just sharing what I know from 37 + years of service.
     
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  8. eslover

    eslover Tele-Meister

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    Holy moly! That’s incredible!!
     
  9. David Barnett

    David Barnett Doctor of Teleocity Ad Free Member

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    Yeah I was running around unplugging things.
     
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  10. Speedy454

    Speedy454 Tele-Holic

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    Thats how electronics in your house get blown up, or at least have a very short life span!
     
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  11. eslover

    eslover Tele-Meister

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    thank you , you know it is a sad state of affairs when a hospital is so worried about their bottom line they don’t have the sense to think about why they are really in business.
     
  12. eslover

    eslover Tele-Meister

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    I’m going to look into the UPS as long as my wife approves .
     
  13. Roger66

    Roger66 Tele-Meister

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    Wow, that much variation, huh? 2 places I have lived in CA, Santa Clara County (San Jose) and Ventura County (Oxnard/Port Hueneme) have very steady line voltages I have a big heavy power conditioner (the GOOD one, I forget the brand) has a digital readout of the voltage. Coming into or out of the box, I dont know. But it never varies more than one volt from 120V. I guess it measures the power coming in, because would it not claim to supply a perfect 120V? I'll check. OK, it's a Power Monster PRO 3500 rack mount unit. The manual says that the display indicates the voltage coming from the wall. So where I live, the power company does an excellent job of supplying 120VAC plus or minus less than 1%, when they aren't busy burning everything down. An LED comes on when the line voltage is less than 90VAC or over 130VAC, Indicating it might not be putting out 120VAC anymore.
    Yeah, If you are biasing other people's amps, I would get one. $300 new. Much less used. It has a capacity of 15 Amps, so that's a 50W Marshall and 2-100W Marshalls, approximately. I should probably plug my old CONN strobe tuner into it, huh. Gee thanks! Now I have to lug that thing around when I tune pianos! Just kidding. Yeah, if you have a problem with unreliable 120VAC, I think that a power conditioner like mine should give you better results. A Variac probably won't work. There might be a Variac model that conditions the power and makes it 120VAC as well. I don't know. It's just an adjustable transformer so I imagine the output voltage is proportional with the input voltage. I hope this helps.
    If it was just for my own amps, I would let it vary until it gets the best tone, then measure the voltage, and use THAT as a target for the correct bias at 120VAC. Have fun! Roger.
     
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  14. kafka

    kafka Tele-Afflicted

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    Residential neighborhood voltage and grounding has been problematic in the past. I haven't really had reason to look at it in the house I'm in now. Electrically, it's the cleanest house I've lived in. But, these residential developments sometimes end up with some pretty funky issues.

    I never gave voltage itself much thought until a few years ago, when the designer pointed out that one of my amps was built for a lower voltage than is typical today. I picked up a variac, and was surprised how noticeable a handful of volts made. It wasn't subtle. I'm not sure I see it fluctuating much. However, although it works just fine at the higher voltage, it's not as optimal as intended.
     
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  15. magicfingers99

    magicfingers99 Friend of Leo's

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  16. Old Deaf Roadie

    Old Deaf Roadie Friend of Leo's Silver Supporter

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    Our town has 5 grids. The grid my job is on shows a 2 volt differential between the B phase and both A & C phases that supposedly traces all the way back to Bonneville. I am more inclined to believe it is more local.
     
  17. eslover

    eslover Tele-Meister

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  18. sds1

    sds1 Tele-Afflicted

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    117VAC constant but the sine wave is clipped badly, therefore rectified B+ voltages are never what they should be for 117VAC into the PT. Would love to figure that one out someday. Power company was no help, guy they sent out could care less about clipping and I couldn't get it escalated.
     
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  19. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    The voltage here ranges from 117 to 123 for the most part. I have seen the odd day at 127 but that is rare. It is very predictable. When all the air conditioners are *on*, mid day, the voltage is 117. When the grid is not stressed, the voltage is 123.

    A variac or a bucking transformer would work fine because the voltage is not varying every few minutes. The difference in voltages are just swinging with the ebb and flow of the aggregate use patterns.
     
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  20. Roger66

    Roger66 Tele-Meister

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    A
    Actually the 60hz is probably more important for the strobe tuner. The 60HZ is pretty stable unless a huge short gravity wave comes by. The motor's speed might be affected
    What?!! The UPS lady in the brown shorts? Hands off, She's mine! And your wife would never approve! Just a minute...OH, a Unvarying Power Supply! Don't look into it too deep, you might get a shock. Don't put ANYTHING into it. Use the blue pill instead! I'm sure your wife WOULD approve of that. God, I Apologise! That's my sense of humor slipping out. Be glad that's ALL that's slipping out! Not like last Sunday at church when.....well, never mind. I dont think it will hit the papers like last month at the PTA meeting! Why does that keep happening? You can't take me ANYWHERE! I will stop now. I Don't know what came over me. I hope it wasn't Bubbles again. I still can't get the stains out of my tutu, and I cannot get rid if that SMELL! It's like a tuna fish eating rotten mushrooms in a swimming pool! Yeah, Bubbles is our local Country Fresh rep, and what a reputation SHE has! I heard that She took ANOTHER cinder block and.... Oh God Kill me now! Might I digress. Yeah, I'd get a used one for a hundred bucks or so. Speaking of used, I can tell you from personal experience, that Bubbles, before she got locked up for good, and since the escape, used to.......
     
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