110 vs. 120

[Charlie]

This is not exactly "radio" related, but the discussion on AC/DC sets and house current brings up a question that i've often wondered. Why is our house current usually referred to as 110 volts when it's actually 120 volts? There's 240 (usually referred to as 220) coming into the house, and then breaks off into the 120 circuits at the breakers. My power here is right on the money at 120.0 volts, and I think I have 119.8 at my cabin.

Are other parts of the country actually running 110 instead of 120 in the house? Or is it just that saying "one-ten" slightly faster than saying "one-twenty"? Or, was it actually 110 many years ago and the "name" has stuck around although it's now 120?

I've often corrected people during discussion when they would say 110 or 220... and when I would say "you mean 120 or 240," they would look at me as if i had six heads. Some would even stick to thier guns... until I'd put the probes in an outlet and show them... it's 120!

Also, this brings to mind the electrical items we buy. Most older items show a variety of ratings. They may say 115, 117, or 105-125 volts. Most modern items show ratings of 120, but ocassionally I'll come across something stating 110 or 117. Of course, I can understand that everyone's power likely varied from one neighborhood to another, but if the standard is 120, why not just label the item as 120?

Also, if you buy a pack of GE or Sylvania light bulbs... either standard or soft white, they are rated at 120 volts. If you buy a cheaper brand of bulbs, they are rated at 130 volts... and usually don't look as bright as the GE's. Why would someone make 130 volt bulbs?

I know... many questions here that really don't make a hill of beans... just always been something I've wondered about.

[OvenMaster]

My Dad says that the voltage indeed was 220/110 way back when, and he still calls it that, even though it's 240/120 now and has been for decades.
*gets up and actually measures wall socket voltage, returns with 122.5*
130 volt bulbs are made, as far as I recall, for areas that have voltage that fluctuate, or will indeed last longer as they're not being fed the "full" 130 volts. I may be wrong, but an approximately 5% reduction in voltage will increase service life by around 15-20%.
Tom

[Dan Starnes]

I have wondered that for years myself, just wondering if they area allowing for a voltage drop?

[Chad Hauris]

Many of the RCA color TV sets such as the CTC-39 and CTC-68 have an adjustment for "normal" or "high" line voltage. To quote RCA, the "HIGH" position is "for areas having a 128 volt AC supply".
I generally put these sets on "high" as it gives a slightly lowered filament voltage for less component stress.

Addionally we worked on a Wurlitzer Jukebox, model 3600 Super Star which had 4 bad output transistors. It had 3 line voltage taps which were like 90-110 v, 110-120v, and 120-130v. It had the tap set on the 90v tap so we switched it to 110-120v. This adjustment was probably provided for the juke when it would be in back-country bars that had really low line voltage. We suspected that the tap having been set to the 90-110v and it operating on the modern 120v ac line caused excess stress on the transistors.

[Nolan Woodbury]

Just stuck a voltmeter in the same wall socket I have my computer plugged into, and it reads 121.3. I've heard from several people in my area that voltage 'peaks' (or is that 'spikes'?) here often, which in the past has caused damage to certain fragile appliances, and has even blown street lights, etc.

If that's the case, what pre-cautions should I be taking with my tube radio sets? What is a good rating for the protective inline fuse?

[Chad Hauris]

We usually use a 1 amp fuse for table top tube type radios, 2 amp for AM/SW consoles and 3 amp for larger radio phono consoles...the fuse however is for short circuit/overcurrent protection and not surge protection. I don't think short duration transients will really hurt tube equipment especially that with a power transformer...however you can use a variac to reduce the line voltage slightly to 110 volts to reduce strain on filaments. You can also wire up a 120 volt to 6 volt filament transformer as an autotransformer in such a way that you "buck" 6 volts off the 121 leading to an output of 115 but I can't remember how you hook that up.

[Nolan Woodbury]

Ok, I now realize it is time to buy a variac...I've probably pressed my luck far enough buying this stuff and just plugging it in. So, which one Chad? If I'm not mistaken, there are many various kinds, like the variacs for guitar amps and such. Can you recommend a make and model?

Thanks for the feedback Chad...yes, it makes sense the input transformer would protect the chassis from spiking voltage...that's its job, understood.

As always, thanks in advance for the help-

[Chad Hauris]

We use the short check lamp (series 60 or 100 watt lamp) to check for shorts but we generally replace electrolytics and paper caps before even plugging in something more than 40 years old. Haven't really used the variac for this
purpose...the lamp will usually alert you i f there is a short (which is usually shorted caps).

Some have reported success with cap rejuvination with the variac but we always just replace. I have tested some of my own tube type equipment using original electrolytic caps (just as a test) that were
working OK and they gradually began to develop problems with use so we find that replacement is best over reforming and using old electrolytics.

Variac is a trade name of General Radio for a variable autotransformer. Also there was an Ohmite "V.T.", and a Superior Powerstat among other brands...I think Superior is the only one still making them...you just need to make sure it can handle the current draw of the load.

Also a Variac (or other such transformer) is not an isolation transformer and you have to watch as on some types you can step up the line voltage to 140 volts by turning the knob all the way up.

Also a Variac (or other such transformer) is not an isolation transformer and you have to watch as on some types you can step up the line voltage to 140 volts by turning the knob all the way up.

Yuppers, YOU WIN THE BIG CIGAR !!

Tom's dad is correct. Years ago the voltage was 110v on each leg.
Then the electric Co's. upped it to 115, then to 117, then to 120.
Put the two legs together from the step down transformer (which is located on the top of the telephone pole) with a resistance between them and you have double the voltage! Neat huh ?

Why did the electric Co's up the voltage? Well there was a reason. I used to know but can't remember now. But I will take two guesses.
1) To make the light bulbs burn out faster for the economy's sake or
2) Voltage is pressure (or force). The higher the voltage- the further you can supply it. That is why the main supply is somewhere between 10 - 20 KV (Kilo volts) Otherwise said 10 - 20 thousand volts. When this flow of electrons reaches where they want it to go , it is stepped down to 120 - 240v via a stepdown transformer after which, it enters your home. You have 3 wires entering your home. Two of which are 120v legs and the third is , what they call now , the nutral (years ago we called it the ground) Soooo, I think that they kept upping the voltage , on the main trunk , to get it out further without having to change all the step-down transformers.

This is the reason DC , direct currant (Tom Edison's idea) , didn't work.
You need AC to use transformers (wheather up or down) and 120v ac or dc will not travel very far. Hence, Mr Westinghouse had a better idea. Wack everybody with kilovolts and hide it with step down transformers.

[electronjohn]

One of the reasons for the original 110V figure was it was the same voltage as Edison's DC system, thus providing compatibilty with bulbs, series-wound motors, etc. IIRC, there were areas in some large cities (NYC?) still operating w/DC power as late as the early 50s. The earliest AC/DC radios were designed to take advantage of the dual power situation, as well as saving some $ by eliminating the power transformer.

[Randy Bassham]

I've got an RCA line voltage monitor and mine runs between 110 and 125 depending on the time of day, I am out in a rural area. Actually the high voltage transmission lines was Nikola Tesla's idea and he couldn't get Edison to see the superiority in the AC system. George Westinghouse was forward thinking enough to see the possibilities in Tesla's system and bought the rights, IIRC he paid several million dollars and then was to pay a royalty of $1.00 per horsepower. Later when Westinghouse was trying to get funding his bankers wouldn't put up funds while the royalty clause was in force. Westinghouse went to Tesla and explained the situation, Tesla was so grateful that Westinghouse had believed in him and his system that he tore up the contract and gave it to Westinghouse. The history of the technology we use today has always been fascinating to me.

[Phil Nelson]

My 1948 National TV-7W television has a two-position line voltage switch on the back of the chassis.

http://antiqueradio.org/NationalTV-7W.htm

[Jeffhs]

Originally Posted by OvenMaster

130 volt bulbs are made, as far as I recall, for areas that have voltage that fluctuate, or will indeed last longer as they're not being fed the "full" 130 volts. I may be wrong, but an approximately 5% reduction in voltage will increase service life by around 15-20%. Tom

Those 130-volt bulbs do last a long time, but when it's finally time to replace one it can be a heck of a job. I once had a desk lamp in which I had installed a 130-volt bulb. The bulb lasted some five years or so. When it finally burned out, the base was frozen in the socket; when I tried to unscrew the bulb, the bulb itself parted company with the base. I threw the glass part of the bulb in the trash, then spent another fifteen minutes (more or less) getting the base out of the socket. The 130-volt bulb lasted too long for its own good, IMHO (at least in a desk lamp) ; I used regular 120(!) volt bulbs from then on until the switch finally froze up. I'd stick to using the 130-volt bulbs in places where the socket isn't easily accessible, such as ceiling light fixtures and the like.

[electronjohn]

Brass base bulbs have a much lower propensity to "seize" in the socket...in my experience, aluminum based bulbs can present the most problems in this area. Wiping the threads with some anti-seize compound can be of help. Break it off anyway? Cut a 'tato in half and use it to get a grip on the remnants. (power off, of course)