230V to 110V, 100V Stepdown and Amplifiers question

bikingbuddha

bikingbuddha

Well-Known Member
Greetings everyone... :)

This morning I was told a very disturbing story by my electronically inclined friend. In fact, it became worrisome to me so I decided that I shouldn't just take his word, I should ask the experts in AK :).

Both my primary amplifiers are running on 230V to 110V step-down transformers. Both are Japanese made in the '70s which clearly states that 100V in the back.

Technics SA-7700ii (100V)
Victor JA-31 (100V)

So far I never had a problem of heating up or anything even though I run them all day long. But my friend told me that they need100V stepdown transformers instead of 110V. Otherwise, it will fry the circuits inside and cook them...! most of the amplifiers he gets for repair are totally roasted because of prolonged usage connected to 110V stepdown instead of 100V. It totally freaks me out because I don't want to destroy them.

Does this really effects...? I mean, as far as I know, they are built to run in between 80Volts to 120V (max) even though it says 100V there.

So far I don't have any issues but should I be concerned about this...? I don't think I can find 230V to 100V step-down converters anywhere in my country because everyone calls this Japanese 110V stuff...! but they are really 100V. If I need a clear 100V I need to get a custom-built transformer to do the job which is going to cost a lot. (in where I live, Definitely not a great place for an audiocholic).

Am I good with my current system or should I be concerned...?

Thanks a lot, AK Folks,
 
Well, the electrical design standard here in the US is 120 volts, not 110, so you are running 20 volts over rated input or around 17%. Hopefully, your area has a little voltage sag.
 
petehall347 said:
have you checked the actual voltage coming out of the step down transformer ?
Click to expand...

Indeed, that should be the first step before a panic.

And, the checking needs to be with the amplifier/receiver turned on because the stepdown transformer output voltage all but certainly will measure higher than expected if the measurement is taken with no load.
 
just been trying to found out the mains voltage tolerance in japan . some say +-10 percent .others say
+-5 percent . as for the frequency that can be 50 or 60hz . best check the equipment rear plate for that .
 
Run some Japanese 100v equipment myself, all of mine have a 50/60hz switch and they are on a 100v step down transformer, and no I would not run them at 110....

With that said, the advice about checking actual voltage at your transformer is very valid, but if they are functioning correctly they are probably 110 or higher.

Also if I was making my own device, I’d shoot for no more than 5% +/- but that’s my very subjective opinion ;)


VR
Andy
 
Sure to be safe, a 100v converter is probably a good investment. (Aren't a lot of vintage US components built for 110 and now running on 120?)

Wouldn't it depend a bit on the circuit? Many Class AB bipolar circuits have a bit of safe operating zone left in their design. But that would only become relevant with high output levels. A lot of IC amp chips have similar voltage ranges and safe operating zones.

In day to day use for average listening levels, wouldn't those circuits be just fine at 10% over rated voltage? You'd have to just be careful to not push the amp into using that last 10% for extended periods.

Now if it was built cheaply with caps and transistors at the edge of their range, then yes that 10% could be the end.
 
Thank you everybody for all your valued replies. I don't have a DMM at my home ( I am planning to buy one in a couple of days) but I do have an analog multimeter with me. So at the moment, I used it to check the output of the transformer and my standard line voltage.

Transformer reading stays at 100V and 98V while the line voltage hangs around 215 to 220V according to my understanding. But I can't trust the old analog meter 100% so I will soon check the above stuff with a reliable new digital multimeter. What I have is a cheap knockoff model as well.

IMG_20201212_102605.jpg

Above is what's coming out of transformer

IMG_20201212_102107.jpg

Above image is my line voltage at home.
 
whoaru99 said:
Indeed, that should be the first step before a panic.

And, the checking needs to be with the amplifier/receiver turned on because the stepdown transformer output voltage all but certainly will measure higher than expected if the measurement is taken with no load.
Click to expand...
Above is taken with no load. So it will be lower with the load! I think I am in the safe zone until I buy a proper 100V transformer.
 
bikingbuddha said:
Above is taken with no load. So it will be lower with the load! I think I am in the safe zone until I buy a proper 100V transformer.
Click to expand...

With ~100V coming from this one you really don't need a different one.

As well, bear in mind output voltage of transformer is also relative to input voltage. If the transformer spec is 230V input but you have just 215-220V input, the output voltage will also be lower than specified. Which, is likely why you have ~100V rather than ~110 from the 230>110 stepdown.
 
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whoaru99 said:
With ~100V coming from this one you really don't need a different one.

As well, bear in mind output voltage of transformer is also relative to input voltage. If the transformer spec is 230V input but you have just 215-220V input, the output voltage will also be lower than specified. Which, is likely why you have ~100V rather than ~110 from the 230>110 stepdown.
Click to expand...

I was thinking the same. Just to make sure, I will take these two transformers to my friend's place who has a power Generator which outputs 230V clean, run it and test the output, see if I get 100V or 110V.
 
I don't know how stable your power in Sri Lanka is, but where I am in New York, our voltage has never varied by more than a couple of volts (at least when I've measured it), typically being 120 or thereabouts. So you might also test your mains voltage to see what it's being reduced from. Step down transformers designed to run US electronics overseas will generally be halving the available power. If your mains voltage is at 200V or so then that's a different issue.
 
swechsler said:
I don't know how stable your power in Sri Lanka is, but where I am in New York, our voltage has never varied by more than a couple of volts (at least when I've measured it), typically being 120 or thereabouts. So you might also test your mains voltage to see what it's being reduced from. Step down transformers designed to run US electronics overseas will generally be halving the available power. If your mains voltage is at 200V or so then that's a different issue.
Click to expand...

Here is an update to my thread.

I have been cautiously monitoring the line voltage for the past couple of weeks and I am kind of lost because it varies like crazy. Normally during the day and night, the voltage drops down to 220V (Checked with a new DMM), goes even low as 215V and the stepdown transformer gives either 100V or below 100V (which is kinda' safe for my equipment but the transformer says 230V to 110). But in the morning when I checked it shows around the 105 to 106 range, which I feel like getting overloaded. I noticed no heat or anything in any of my equipment but I switched them off just to be on the safe side.

I am sure you might be wondering "How hard is it to get a proper transformer...?"

Well, it is pretty hard because stuff we have in stores is cheap shit built by ultra low-end Chinese manufactures which gives hums and crazy voltages (I don't trust them with my equipment). Yesterday I went to this used equipment guy and found out a wonderful little transformer rated 1000watts made in Italy which is supporting many input and output voltage types.

I didn't buy it because it didn't have the 100V support, only 90V and 100V. If I run Japanese equipment on 90V, will it bad...? I tested with DMM and it gives around 92.
 
I feel like 106 volts (6% tolerance) would be safe for a 100v component, but given the instability of your mains power supply, there's no guarantee that it's the max you'll see. I think what you should be looking for is a power conditioner, it should give you a stable 220V-230V AC supply, which you can then step down to the appropriate voltage using a reliable step down transformer.
 
bikingbuddha said:
I am sure you might be wondering "How hard is it to get a proper transformer...?"
Click to expand...

It's not hard to get a transformer of a particular ratio but as swechsler says, if your mains voltage is all over the place there is nothing a conventional transformer can do, other than "transform" input to output in the fixed ratio of its design.

Problem isn't the transformer; problem is the swings in your mains voltage.

A Variac can adjust for the ups and downs in mains voltage, but with that carries possibly even more risk. If the mains voltage is low and you boost it up with the Variac, then the mains voltage rises, the Variac doesn't know that and boosts the voltage even higher until you readjust it down. Then, after it's adjusted down, and the mains again reduces, you'll be low again. A vicious circle.

With that sort of mains swing, I agree an automatic voltage regulator is worthy of consideration.
 
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Aren't a lot of vintage US audio components designed for 110v and running on 120v? For a straight class AB amp, I don't see a real crisis with 10% either way. Those circuits aren't particularly voltage sensitive. Maybe dial the volume back when the line is running high at off peak hours. I'm open to being corrected on that.
 
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