Brown-out Power Problems

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Svart

Well-known member
Joined
Jun 4, 2004
Messages
5,134
Location
Atlanta GA USA
wow, is that a constant drag on the AC or quick dips in AC? quick dips of course can be fixed with capacitance but for long drawn out dips I don't think there is much you can do other than some kind of active regulation. the PRR varimu design is of course not regulated actively and this is one of the drawbacks of this implementation. you might try adding some Vregs to the outputs.. I did this with mine just as an experiment and while it does not change the audio one single bit it might regulate your rails better.
 
[quote author="buttachunk"].... this has been over 20 hours. Maybe there is some kindof active Variac to keep voltage at 120VAC ?[/quote]

That's what a proper power conditioner is/does.

Are you sure it's the grid that's having problems or could it be your drop or panel? How's the neighbors power?
 
> AC has gone down to 108VAC

This kinda crap happens. Which is why I hate to see "48V regulators" with nominal 53V input. Sure it works when the line is 120VAC, but it gets goofy at 118VAC, and lame when the backhoe meets the power cable and the patch-around only delivers 108VAC (as my city has been for parts of 2 years). A "regulated" supply that needs the regulator to filter the ripple will be NASTY when the regulator punks-out for lack of excess voltage to waste. Regulation means starting with LOTS of excess voltage, like 1.5X desired voltage, so line-dip and ripple and other crapola never lets the regulator drop-out.

As I'm sure you understand, a manual Variac set to crank 108V to 120V will be BIG trouble when the utility power comes back to normal: 133VAC!!!

Auto-variacs exist, unfortunately. One theater here had one that bobbled 115V-117V-115V-117V-115V-117V all day long. Such devices are widely used by utility companies, though most are better adjusted than this one was. Fortunately, they don't make one you can afford.

Constant-voltage transformers exist. The cheapest model puts out a round-square wave, good for lamps but not for DC toys. Most now are waveform corrected and make clean sine-like waves. They have a minimum load, they run HOT even when unloaded, they are HEAVY, and cost a lot.

Some computer UPSes will correct voltage. The very cheapest don't, unless it fails. Another class will make minor trims, using the inverter to boost/buck the line. Only expensive ones do this clean enough to use around audio.

Put on your mittens, wax your sled, and go play in the snow.
 
I don't know, our Gen Rad auto clunker has been going for 15 years now, just a re-cap job.

You could variac or transformer your 108 up to say, 118, then when power comes back up, hopefully to 120, whcih you know it won't, you will only have 130 volts til you catch it.

With step down transformers (solid state), you would blow anything up. Tubes supplies might be a different story, caps, etc.
 
there is an obvious solution but one that seems to make everyone cringe even though it's not *that* bad..

Switching PSU. most can handle everything from 80-240vac and if they are a good design will not add much noise if at all.
 
Besides the "auto variac" and constant-voltage transformer types, I have experience with another type of AC line voltage regulator. In our TV truck, we have a big isolation transformer followed by an equally large rackmount regulator that works by switching taps on a multitap transformer or autotransformer. The switches are fast and seamless--the equipment in the truck doesn't blip or glitch the slightest even when the regulator is switching away like mad. I assume it's switching on the zero-crossings.

It's a pretty cool device... I'll try to remember to grab the make/model # next time I'm in the truck. I'll bet it costs a bundle, though.
 
How about a step up transformer that is rectified to power a 60Hz oscillator that is adjustable to +/-60AC 180deg phased outputs into another xformer with a center tap on the secondary?

That way you could use a voltage regulator. I'm guessing you could have your ground isolated that way by using +/-60AC (hot and neutral) and center tap floating as ground. Fuse heavily. Might need a new panel after that rig.

Might wanna check your electrical code on that one. :wink:
 

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