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Discussion of precise voltage measurement

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

WarrenS

Mon, Oct 10, 2011 8:01 PM

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:

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.
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.
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..
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.
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

Hi,

I picked up a dead 7075 recently, I found that the fuseholder was not making
contact with the fuse, fixed that fault and now the PSU area was making a
fizzing noise. I disconnected the mains straight away. I presume I need to
reform the main capacitor with a dropper resistor. Is 33k a suitable value,
or should it be done at a lower current than that?

Regards,

M K

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 ***************** Hi, I picked up a dead 7075 recently, I found that the fuseholder was not making contact with the fuse, fixed that fault and now the PSU area was making a fizzing noise. I disconnected the mains straight away. I presume I need to reform the main capacitor with a dropper resistor. Is 33k a suitable value, or should it be done at a lower current than that? Regards, M K

Poul-Henning Kamp

Mon, Oct 10, 2011 9:30 PM

In message 4EF131EAEF2E45BA8C7658C73574525B@Warcon28Gz, "WarrenS" writes:

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.

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
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

In message <4EF131EAEF2E45BA8C7658C73574525B@Warcon28Gz>, "WarrenS" writes: > >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. 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 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.