[volt-nuts] Safe power-up. was (Solartron 7075 ...)

gbusg gbusg at comcast.net
Tue Oct 11 00:55:07 UTC 2011

I like your test method, Warren.

Regarding switch-mode power supply issues: Once or twice a year we had power 
brown-outs in the neighborhood where I used to work. The lights would dim, 
but power wouldn't necessarily cut-out completely right away. You could hear 
various computers and pieces of equipment intermittently beeping or humming, 
and relays clicking in some equipment. At that point we would manually 
turn-off all equipment as quickly as possible!

After power returned to normal and we turned everything back on, there was 
about a 50% chance one or more HP 8662A signal generators were smoked. The 
problem was always the switch mode power supplies in them. Most HP equipment 
seemed to survive the brown-out, but, based on those experiences, I would be 
leery (if not downright afraid) to try running a 8662A on reduced AC primary 


----- Original Message ----- 
From: "ws at Yahoo" <warrensjmail-one at yahoo.com>
To: <volt-nuts at febo.com>; <time-nuts at febo.com>
Sent: Monday, October 10, 2011 4:00 PM
Subject: Re: [volt-nuts] Safe power-up. was (Solartron 7075 ...)

Power factor correction power supplies has not been a BIG problem with my
OLD recycled equipment.
I tried to Cover that case in my end note,
With switchers, turn the variact to normal and use the other safety features
and a big enough light bulb to keep from blowing it all up if something is



Poul-Henning Kamp phk at phk.freebsd.dk

>In message "WarrenS" writes:
>I don't plug ANYTHING new to me, directly into the line the first time I
>(especially if it had a blown fuse)
>Here is the solution that I use for a universal, general purpose, tester
>Old (and new) equipment.

That procedure is fine for linear power-supplies, but not resonably
modern switch-modes.  In particular, anything that has PFC correction
is not going to respond too well to variable voltage like that.
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20

> I don't plug ANYTHING new to me, directly into the line the first time I
> try
> it.
> (especially if it had a blown fuse)
> Here is the solution that I use for a universal, general purpose, tester
> for
> Old (and new) equipment.
> This is a great tool that can be used for trouble things that draw too
> much
> current, has shorts, for reforming caps, Testing line voltage sensitivity
> etc, etc.
> First time powered up test equipment is powered from:
> 1) A line voltage rate light bulb in series, starting with a low wattage
> and
> working  your way up.
> The light bulb acts Nonlinear variable dropping resistor, which act like a
> current limit and will limit the max current to a safe value but still
> have
> minimum effect at lower currents due to it's Hi TC.
> 2) The voltage to the Light bulb comes which from adjustable variact.
> The voltage rise and the Time at each voltage setting is a learned
> function
> and depends on what is being tested.
> If you're in a hurry, set it to the nominal line output and flip the
> switch.
> The rest of the stuff will still provide protection.
> 3) The Variact is plugged into a KillAwatt meter
> Used to constantly monitor the power, If it shows too much power is being
> used, ... Well don't let it do that..
> 4) The Kill-a-W is plugged into a solatron 1 to 1 line regulating
> transformer.
> My Line regulating Solitron has the very desirable built in characteristic
> that it goes into a saturation mode that limits the max output power if
> overloaded
> If not overloaded, it outputs a constant voltage.
> 5) Have a few resetable and/or  standard  fuses in there to be over safe.
> The proper use of the variact's output voltage has a learning curve,
> because
> equipment with switchers behave differently than things with linearly
> supplies
> ws
> *****************

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