110v down to 100v power converter, is it stupid?

I had been electrocuted by 220 and by 110. Both suck, but guess which sucks more?
Below 50 V many people don't even feel. And if the fuse blowing current goes through us we would be totally fried. About 0.1 Amp is already fatal, and no fuse can protect from that. People not always killed by high voltage, for example static electricity (can be a few thousand volts) just give us unpleasant shock, but the voltage drops instantly and no significant amount of curren flows. Also it is critical if the curren goes through your whole body or just a part of it.

 

Aren't most devices designed to operate +/- 10% of rated voltage?

 

absolutely.

 

"It depends" on what is or isn't safe a great deal. Most tube equipment will run on ten or fifteen percent high or low voltage, but the life of the tubes and other parts will vary a lot in some cases. Tubes tolerate high plate voltages pretty well, unless the design runs them at the limit already, but high heater or filament voltages are bad for tube life. Solid state gear ( not switchmode) usually has some linear regulated internal supplies and the higher the voltage the more heat they have to sink. Switchmode supplies usually work very well over a 30 to 60 percent range of voltages.

Low voltages can be bad too. It's tough on motors, but also some other items-any tubes with bright filaments (transmitting types usually) will die a young death with low filaments.

So the question can only be conclusively answered by going over the circuit carefully. But in general, running them at marked voltage is always going to be safe.

 

You should not assume what your mains voltage is. Check the voltage at the wall power receptacle outlet with a volt meter. Usually I would tell you to check the voltage at the receptacle with all loads turned on that are connected to the receptacle. But because of the 100V voltage rating of the equipment an unloaded voltage reading would be better in this case. Check voltage with no load connected.

The voltage at my home typically averages around 120 to 122 volts.
If you use the 10% over voltage, many here have posted, then the maximum allowable mains voltage would be 110V for the 100V equipment.
115V would be 15% over
120V 20%
If the voltage at the receptacle is 120V the higher voltage will cause more heat to be generated by the 100V connected equipment. That heat could/ may cause premature equipment failure.
P = I x E
P, power, (watts, Va)
I, amps
E, volts
For your 100V audio equipment (I) is the constant. Raise (E) and watts, Va, goes up. More power = more heat.
(This does not necessarily hold true for switch mode power supplies.)

It's your equipment. If it were mine I would install at least an autotransformer/ or isolation transformer wired as a Buck transformer and lower, (step down), the voltage to 100V. (When an isolation transformer is wired as a Buck transformer it becomes an autotransformer.)

 

I was amazed at the lack of power in Tokyo
90 vac seems really feeble for a high tech country
Their overhead power supply cables look a nightmare...

 

Of course! I want to take care of my stuff that's the reason I asked for advice

 

Yes, but wiring an isoformer that way will give you 50% voltage, which isn't what you want either.

Some isoformers have a third winding that gives buck and boost voltages that are lower and higher. But they can be 5%, 10%, or who knows what so you have to measure. This was common in units made for TV repairmen in the seventies and eighties. The RCA (later VIZ) Isotap units were especially good since they were potted and survive a couple of decades in the garage pretty well, even if the case is rusted. Rustoleum will make it look a lot better if it is.

 

If the OPs mains voltage is 120v he can use a buck/boost xfmr and buck the voltage 20% from 120v to 100v

http://www.buckboostcalculator.com/

The OP will need to figure out how big, KVA, xfmr he needs. The above calculator will tell him which xfmr he needs.
Jim

 

I just imported an Onkyo stereo receiver from Japan (cheaper than ordering it from the USA, go figure) and my house mains voltage is 110v.

The receiver gets warm (but I'm using 5ohm speakers with the built-in 4ohm switcher option). It gets hotter during the day (not scalding hot though) but I think that is because my city's climate is on the tropical hot side and has a high humidity. At night is just a little warm and I have noticed a sort of mild odor (like a metallic candle!)... is this normal?

Will those extra 10v reduce the receiver's life?

 

Could. Referring to the schematic, is there a switchmode or linear supply there? Although ten percent is probably (just) within design spec.

 

In the amp? Or in my house mains electricity? The receiver just specifies 100v on the back.

 

Yes, is it a linear or a switcher supply in the amp? That's why you always want the schematic. It answers many questions. In general, switchers have a wide input voltage range. Linear supplies tend to run hotter the higher the input voltage. The pass device has to drop more voltage.

 

Sorry, I don't know. It just says 100v in the back without specifying any wider range.

This is it:

http://www.amazon.co.jp/ONKYO-ネットワー...&qid=1421357688&sr=8-1&keywords=onkyo+tx-8050

There is a photo of the back of the receiver.

 

Did you check the voltage at the wall receptacle the Onkyo stereo receiver is plugged into with an AC volt meter to verify the voltage is 110V? If not I would recommend you do so. If the receiver has a standby mode take the voltage reading with the receiver is standby mode first and then take it again powered up.

 

Hi Burt,

Seeing this old thread again got me thinking about what a transient voltage spike caused by an appliance starting up would do to the power supply and subsequent output power of the power supply of a piece of audio equipment that is rated for 100V only when it is connected to say 110V or 115V? Given enough transient voltage spikes and passing time will it shorten the life of the equipment quicker than it would if the mains voltage was reduced to it rated 100V.
Jim

 

I haven't checked the voltage. Will do so. Thanks for the recommendation.

 

My receiver is getting very hot now (well, if I don't crank it up, it only gets warm). But then, Onkyo is infamous for the heat issues so, I don't know if it's a normal temperature.

I better get a variac; for an added peace of mind,

What do you guys think about this one?

http://www.amazon.com/dp/B006NGI8VS?psc=1

 

Remind me not to purchase any used tube gear from you guys

 

Could I please make a train spotter comment re: "electrocution". This word indicates that the person would be typing from somewhere not of this Earth - it's not a recoverable position.

 

a little side step. I am thinking of importing an integrated amp from the UK rated at 240v. Do you think a step down
transformer might affect the sound quality? I have read several articles that suggest this and would like some opinions.

 

A cheap nasty one might degrade the sound, but a decent quality one will not degrade things.

 

You need to take some step to adjust your power supply (from mains) voltage
Mains voltage (at the wall) here in the U.S. can easily run as high as 125

THAT is NOT safe or acceptable if your equipment is in fact designed to be operated ONLY on 100V! And as another poster mention, Japan also uses 50 AND 60 Hz depending on location
(this could be a good thing however, see below, as to the possibility of one transformer being used on the assembly line for models going into multiple markets) Japan also uses 120V 60Hz on military bases at Okinawa

"Running" all those ICs involved with CeeDee players and the like (beyond the CIRCUIT'S rating) will cook them to death, even if the player seems to work fine ("amps" doesn't tell me enough, but my comments apply here as well All depends on the design and parts used in the power supply as to what you can do to address this) Don't know the vintage of your amps either, are they modern types with a lot of ICs or are they discrete designs?

You have no way of knowing what the "margins" are unless you have a schematic, service manual or some other way of determining the rating of the devices entire architecture (chip compliment and implementation especially)

Sometimes the rating labels are what they are (the numbers) simply to discourage the unit from being sold into another market as has been mentioned (I own a turntable where this is the case; I also have the service manual for it and the actual circuit/transformer and motor are identical for EVERY model variant, EXCEPT for the way, and the ratings of the safety caps employed where the main's cord enters the chassis and includes a switch for units being sold into the 220-230V markets (but the switch IS NOT end user "accessible"

In other words, addressing different country's safety codes as for the caps (the Canadian version uses 3 where the U.S.A. version only 1 but the TOTAL capacitance is the same! And we both use the same voltage (120V @ 60Hz) The Canadian cap values also call for a higher voltage rating on the safety caps

So, my point is: open the units and or get a service manual (because there MIGHT be an internal switch for voltage (but I doubt it, unless this is some very high end gear, thinking mainly the CeeDee players)) OR with the aid of a schematic, you or a technician (I do not know your abilities) may be able to change some wires to different taps on the power transformer IF the transformers are all one in the same for the purposes of the assembly line (one part number for the manufacturer, just wired to different taps for different markets).............you get my point

You need to look at it more closely and KNOW exactly what you have and then decide/KNOW from that what you need to do

But just plugging it in and going on Faith is NOT the way to go, even if the players work

It is worth a close look; you MAY be able to address the voltage difference problem with a service manual and a soldering iron. If NOT then at least you will know, in SAFETY what has to be done

In a pinch, you can (but you did not hear me say this) "adjust down" line voltage to the transformer by installing TWO inrush limiters on the primary taps of the power transformer if this is practical on your amp(s) I've done it on tube amps; first for the obvious, to protect my amps (tubes) from the massive, COLD current inrush, but a secondary benefit is that the limiters I use have enough internal resistance to drop the voltage in a stable and reliable way precluding the hack job of adjusting mains voltages with a power resister and do not appear to introduce any noise on my supply

But look closely first; you may be able to solvve your problem with no outboard solution! (hassle or financial expenditure)

Analogman

 

Halloween Jack,

Did you ever check to see what the voltage at the mains wall receptacle is?

I personally would not use a variac to compensate for a constant state overvoltage condition.

You first need to check the voltage at the mains wall outlet receptacle then you can determine how much voltage reduction you need from the mains voltage for your receiver.

A buck transformer will perform better than a variac set at permanent voltage reduction point imo.
Jim

 

I would think the thing to do first is to get a little more SPECIFIC information about his equipment before he starts looking at any hardware/transformer solutions............may not even need it

Analogman