Question for USA residents: What's your AC Mains voltage at this moment?

I'm hoping to get a feel for what everyone else experiences.


I am working on a guitar amp this morning and the plate voltage is 460vDC... too high.

Friday it was 445vDC... just a bit high.



So I figured I better check the mains voltage and sure enough it's 124.7vAC at the moment.





Maybe I should turn on the heat and open the windows?




best regards,
mike

Interesting you should ask. 

In the past I have seen 120 average...BUT... I just checked since I have a meter downstairs monitoring something else for a few days.....

It was 126.2vac. I have never seen it that high. I know a local town runs intentionally at 124 but I'm not on that system. 

Measuring with a different meter.... 125.6 on that outlet, and 122.4 at the other end of the counter on a different circuit/phase.  Still,  both are running a bit high. 

Thanks everyone.


best regards,
mike

"I always test my amps at 117 on the variac."


It occurred to me that some might... and that I might should. :-)

Mine is 123 right now. Varies between 120-124. I guess they allow 5 volts difference.

Never low though.

Yes, but a UPS that can handle everything costs quite a bit as I went through that list someone posted the other day, I figure dirty power is more of a concern than a few voltage points, if it stays within the parameters that it is suppose to be. (5 volts I have read.)

10% is acceptable for MOST electrical things but it is also centered on 120v. 

Most utlilty companies now like to run a bit on the high side to keep their commercial customers happier. Motors and electrical heating are a bit more efficient when run slightly on the higher side of nominal.

At least that was the explanation I got from the city crews here.

Maybe I should test and setup at 120.
117 seems to be a good balance here in the North West.
When I was first starting out I had a Soldano HR-50 that had "117" under the AC receptacle on the bench. Seemed right, here in Seattle anyway.

I guess that's why I settled on 117.

Tom

Too high?
Leo never was never afraid to run the 6v6 hot (plate voltage, not bias point).
"If I set the bias to get a good current draw at idle", so you can get the bias point right.
What was the factory/stock current draw?
Must of been pretty high if it was pulling the B+ down significantly.
Where is your B+ at?
You could put a big wire wound resistor first in line and "pull" your B+ down a bit.
I'd have to dig to find notes on the last Princeton I had on the bench, Silver Face 70's;
never fussed with any of the Fender reissues.
The old ones never had a choke, just 1k after the plates. Of course just the screens and pres behind that.
But a low value wire wound would be like some of the stuff that has the choke first.
I guess it all depends on how hot, hot is.
420v on the late 60's Deluxe and Princeton schematics...

tom

I spoke too soon. Dipped to 118-119 volts for a few seconds. Went back up to 120-1 then after that. (??)

For those of you who don't "get" what Mike and I are talking about, Mike has 3 problems here.
1) He has too much B+ (that is the 450vDC we are talking about).
The spec on the 6v6 is about 350v max on the plate and 14 watts dissapation; that's 40mA current draw at 350v.
Fender commonly ran the 6v6 up to 420vDC, but NOT at full 33mA dissipation.[450v x .0333A = 14 watts; this is not the output, this is the tube idling, HOT].
2) The bias supply will not let him lower the current draw on the NOS tubes. The "spec" Fender gives is -34v, (this varies widely, especially in current production tubes) but there is a "pot" so you can adjust the bias point.
He doesn't give us the range, but it won't go "negative" enough.
We "bias" a tube by pulling the grid (input) negative, relative to the cathode.
Since this is a class AB, "fixed" bias amp the cathode is at ground.
The farther "negative" we pull the grid, the less current the tube will draw, hence the term "run cooler".
And this introduces problem
3) the lower the current draw, the less the B+ will drop, so we have more voltage.
And just to confuse the issue with the facts...
In the preamp we would "ground" the grid and "lift" the cathode above ground with a resistor.
And actually there is a resistor to ground from the grid because if we really "ground" the grid we turn the signal off, but trust me the tube "sees" the grid as negative relative to the cathode.
I'm not "really" an engineer, I just "accept" all this as true (kind of like the world is round, looks flat to me; or the universe is expanding, whatever)
The amp "works", that's all I care about.
Someone, maybe John (ampfixer) will chime in if I have any of it wrong and are misleading you, someone I'm sure will straighten us all out.

Class dismissed!

T

As for the O/P question, We have the exact problem in Canada as you describe. One of the biggest reasons for high line voltage is urban expansion. As the electric grid expands you start to get low levels as the load increases. Bad grounds and bad insulation cause wacky line levels also.

To fight the low line levels they can crank up the voltage taps in a power station but those that live closer to the source will get high line levels. As the infrastructure degrades and power demand increases it will get worse. Can't build nukes, can't burn stuff, and we are way behind Europe on alternative energy. Hmmm, thinking..... Nope I got nothing.

Mike,
Drop a 5Y3 in it, here is what I saw just now in my 15 watter.
AC 118v
Rectifier   Standby         On             EL-84's
5Y3          377vDC    349vDC     23.3 & 22.3mA
5AR4        384vDC    361vDC     27.0 & 25.3mA
Both rectifiers are Sovtec's.
Just for S&G's I dropped a "real" GZ-34 in her, it tested exactly the same as the Sovtec 5AR4.
But, Mullard just has a sexy ring to it; doesn't it?
My preamps are "ON" all the time, about 14mA in this amp (3 AX & 1 AT).
I lift the cathodes of the output stage off ground in standby; I don't interrupt the DC.

Tom