Power Supply Needed

[QldKev]

I'm chasing a power supply 16vac 500mA but cannot find one. (note AC output not DC)

I believe the original item is also a regulated power supply, it is made by Xing Yuan Electronics part# YP-088. The OEM is designed for 110V US power source.

Pic of OEM power supply,


Anyone know where I can get one designed for Australia.

edit: I have one of these on order so I can use the OEM for now, but would rather a straight power pack.

QldKev

 

[barls]

this ones pretty close
http://www.jaycar.com.au/productView.asp?I...UBCATID=1000#12

 

[QldKev]

Thanks, looks pretty good.

I wonder how I can tell if it's a regulated power supply? I guess if I buy it, then I could always test it.

 

[newguy]

Thanks, looks pretty good.

I wonder how I can tell if it's a regulated power supply? I guess if I buy it, then I could always test it.

Electrical engineer here. "Regulated" means "can't or doesn't change", referring to the output voltage. AC, since it's a constantly changing wave, is actually quite hard to "regulate" in the sense that you try to keep the voltage wave maxima a constant value. It's possible, but very unlikely to be found in a small wall wart supply such as the one you're looking to replace. Long story short, your supply isn't regulated, so don't worry about finding one.

 

[QldKev]

Electrical engineer here. "Regulated" means "can't or doesn't change", referring to the output voltage. AC, since it's a constantly changing wave, is actually quite hard to "regulate" in the sense that you try to keep the voltage wave maxima a constant value. It's possible, but very unlikely to be found in a small wall wart supply such as the one you're looking to replace. Long story short, your supply isn't regulated, so don't worry about finding one.

The supplier of the amp (headphone amp, hence the small values) that uses the power supply mentioned the OEM was a regulated power supply, I only read it in one post and I can;t find it now. With the OEM being a 500mA unit, we know the amp has a max input of that. With the 16vac 1.25amp version of the power supply I was just a bit worried with a draw <=500mA it would still be outputting a lot higher than the 16v. I've also sent the manufacturer a pm (on another forum) to verify if it is indeed regulated and if the Jaycar one would be ok.

 

[pcmfisher]

The voltage should be constant regardless of load.

The 1.25A is the maximum load, so 500mA is fine.

 

[QldKev]

As newguy mentioned AC power supplies are unregulated. Only some DC supplies are regulated. So it seems in the forum where the OEM mentioned it was regulated must have been in error.

Since it's unregulated the voltage will increase with a decreasing load.

@newguy without plugging the amp into the power supply to measure the voltage and risking damaging it, is there a way to calculate what voltage the supply would give at the load?

 

[newguy]

@newguy without plugging the amp into the power supply to measure the voltage and risking damaging it, is there a way to calculate what voltage the supply would give at the load?

If you have an assortment of power resistors and a voltmeter, yes. Connect different Rs, measure the V, plot the results. Whatever your amp is rated to "pull", use that to calculate an equivalent amp R, and look up in chart the V to see if it's good.

I do have to say that I doubt that your amp is so poorly designed that it can't tolerate a little power supply swing. A more prescient question for the manufacturer would be what kind of power supply swing it can tolerate. The replacement is likely A-okay.

 

[QldKev]

Ended up getting onto a tech support person from Jaycar. Told him the spec for the amp is 16vac 500mA (8w). He got one of the above power adapters applied a 32ohm load and measured the voltage, it showed 18v. They also have a 15vac version, which rates to 17v with the same resistance. He did say that it should be ok, but since it isn't the exact spec to be careful as the OEM would likely void any warranty should it be needed. He recommended using a 240v to 110v step down transformer, and then using the supplied power pack.

I did send a message to the company who makes these (actually the main person who designs them) with a reference to the 16vac power supply above asking if it is suitable and within spec, but he has not replied.

QldKev