Stable AC Voltages For Testing?

[syscokid]

I don’t know what I’m up against. Our whole area is like this but our household AC voltage fluctuates from 117v to 124v. Sometimes, I’ve seen in a span of 15 seconds, the voltage fluctuate from 120 to 123 and then back down to 120 or less. It gets a little frustrating when testing amp voltages. I’m looking for a very affordable solution. Is it possible?

[Cartman]

Furman makes one, but very affordable?

https://www.amazon.com/Furman-P-1800-AR ... B001UNPCCM

[martin manning]

An inexpensive Variac, 1kVA, would take care of that.

[WhopperPlate]

An inexpensive Variac, 1kVA, would take care of that.

It won’t stabilize the voltage automatically, but you can certainly keep things under control with you keep your eye on the voltage meter .

Even with a regulator , afaik voltage regulators that I have experienced have a threshold as high as +-5vac before they trigger an auto adjustment .

Beyond the kikisui power supplies that guys like bonamassa and angus young use , which are several thousand$ each, anyone know of any voltage regulators that actually regulate ?

[maxkracht]

Least expensive options are: do work in the middle of the night when the grid is more stable, or stop caring about the fluctuation. I will ride my variac when biasing or writing down measurements if the grid is extra wiggly, but grids going to wiggle, so don't worry about it. Uness you live somewhere that goes high enough to cause damage, it's probably not an issue.

[R.G.]

You need a "constant voltage transformer" or ferroresonant transformer. These things produce an AC output that is nearly fixed over the ranges you describe. They used to be cheap on ebay, but I haven't looked for a while. You need one described as "harmonic neutralized" and rated for enough power to do the work at hand. A 100W tube amp might work well on a 500W ferro.

This one looks like a relative good deal: https://www.ebay.com/itm/335044593891?h ... R-z_pserYw

750VA 120Vac out, 9A output. $50 and $40 shipping (they're heavy!)

[syscokid]

Furman makes one, but very affordable?

https://www.amazon.com/Furman-P-1800-AR ... B001UNPCCM

Besides questioning one's interpretation of affordable, ha ha, this is what I caught from its product prescription: "The P-1800 AR accepts input voltages over a wide AC voltage range and transforms it to a constant output of 120V, +/- 5V."

Least expensive options are: do work in the middle of the night when the grid is more stable, or stop caring about the fluctuation. I will ride my variac when biasing or writing down measurements if the grid is extra wiggly, but grids going to wiggle, so don't worry about it. Uness you live somewhere that goes high enough to cause damage, it's probably not an issue.

This is probably the most practical, and definitely the most least expensive solution. I've noticed that very late afternoon/early evening the AC voltages cruise along at 119 to 120 for a while.

You need a "constant voltage transformer" or ferroresonant transformer. These things produce an AC output that is nearly fixed over the ranges you describe. They used to be cheap on ebay, but I haven't looked for a while. You need one described as "harmonic neutralized" and rated for enough power to do the work at hand. A 100W tube amp might work well on a 500W ferro.

This one looks like a relative good deal: https://www.ebay.com/itm/335044593891?h ... R-z_pserYw

750VA 120Vac out, 9A output. $50 and $40 shipping (they're heavy!)

Wow! I might just go for this. Thanks! I hope it's as simple as it looks...

[martin manning]

Wow! I might just go for this...

OTOH, it's a one trick pony, where a Variac has many uses.

[R.G.]

You're right Martin. It does one thing only - it takes in AC power on the primary side with a wide variation of voltages and produces an AC output with a small range of voltages. Depending on the design of the CVT, it may be able to take in 90-130Vac and turn it into 120Vac +/- 5% to 10%.

Variacs take in some voltage from the AC mains and convert it to any voltage between 0 (-ish) to a bit higher than the input voltage.

I've always thought of CVTs and variacs as complementary - one makes a mostly constant AC voltage, the other lets you vary the AC voltage over a very wide range.

[syscokid]

Wow! I might just go for this...

OTOH, it's a one trick pony, where a Variac has many uses.

A heavy one trick pony at that. 50 lbs? Maybe 70 lbs? Ouch!

An inexpensive Variac, 1kVA, would take care of that.

It won’t stabilize the voltage automatically, but you can certainly keep things under control with you keep your eye on the voltage meter .

A variac is starting to sound like a decent compromise. Most of our AC voltages hover above 120, rather than below 120. More research…

[syscokid]

Anybody’s thoughts on this China-made variac out of Arizona with free shipping?

IMG_1081.png

https://www.circuitspecialists.com/tdgc ... 47c6d56d2c

[martin manning]

A 10A would be big enough, and much cheaper.

[syscokid]

A 10A would be big enough, and much cheaper.

Yeah, you’re right, but the next step down from this particular vendor is 5A! The deal is decent considering the shipping is included with the price you see. And I like the LCD that shows voltage and current at the same time. I’ll look around a bit more.

[WhopperPlate]

Depending on the design of the CVT, it may be able to take in 90-130Vac and turn it into 120Vac +/- 5% to 10%.

I've always thought of CVTs and variacs as complementary - one makes a mostly constant AC voltage, the other lets you vary the AC voltage over a very wide range.

Whereas the price point is obviously worthwhile to consider in comparison to the Furman, but we are still looking at that +-5-10% … so if you want precision a variac is still necessary, which again doesn’t auto regulate, unless you can hire a guy to sit there with his eyes on a volt meter .

My interests in this subject lie mostly within the live sound world , where fluctuating power causes the most headaches . Still the only thing I have seen that fits the bill there for precision voltage control is the kikusui power supplies . Not cheap. These are the 2000va model . They have smaller units.

https://www.google.com/search?client=sa ... =sivnmbhtz

[syscokid]

I just pulled the trigger on an old school Staco 3PN1010 in decent condition. The title of the Ebay ad was goofed up:
https://www.ebay.com/itm/305369048146