Triple failure. Software? Hardware? Please help

micky wrote:

A lot of things were done to make color tv's portable in that way.
Including getting rid of the high-voltage cage. That still scares me
a little, but as one who has to drag the tv that just broke out of the
basement and drag another CRT tv down there, I'm glad they are lighter
than they were.

I remember an office full of CRT monitors sitting next to each other
that would twitch like clockwork because the flybacks caused
interference, and this would happen even when they were 6 feet apart.
OTOH most of our own monitors could sit right next to one another and
not twitch, and almost all of them had high voltage cages or cases
that were copper plated. One of them without much of a cage instead
had an extra winding on the flyback that was connected to nothing but
a 1/4" x 3" circuit board that sat by itself -- an antenna to put out
an out-of-phase signal to cancel interference.

larry moe 'n curly wrote:
Bill in Co wrote:

I can still remember the days of the cheapie, "hot chassis", "All
American
Five" tube radios. "hot", because they ran directly off the mains line
voltage, without using a power transformer for any isolation from the
power
mains (to save money).

I have a 35-year-old TV built like that -- still works, has needed
only 2 capacitors and its flyback connections soldered (not resoldered
-- originally wire wrapped). Then about 15 years ago I bought a new
TV with direct video and audio inputs and thought it would be
transformer isolated, but instead they used optical isolators on those
direct inputs. 4-5 years ago, I got rid of that TV only because the
case had become so brittle that I thought it would one day suddenly
collapse from the weight of the CRT.

I wonder if the current generations of TVs even use a power transformer. I
think it's a good idea (for the simplest isolation), but I'm old school.
:-) I suppose if someone had a 1000W TV, the added bulk might be a
consideration.

micky wrote:

On Sat, 9 Jul 2011 01:48:42 -0700 (PDT), "larry moe 'n curly"
wrote:

Some PSUs, especially old ones like that and the newer high efficiency
designs, don't regulate their voltages very well at light loads and
may require draws of several amps before they work right.

As to my not connecting anything but the mother board, not the other
outputs too, surely the floppies and the CD drives use almost nothing
when they are not in use. The hard drive would use somet. Do
computers with cheap power supplies have a hard time displaying the
entire POST or the Setup/BIOS screens if there is no harddrive?

Or are the fans enough?

Every computer will start with just the motherboard installed because
every time I get a new mobo, I first test it without any drives
installed. A mobo applies a bigger load than a hard drive. BTW a
very few mobos won't boot at all if the clock battery is dead or
missing.

Fans typically draw just half their rated amps, and I think you'd need
5-10 of them for a decent load. Some people build PSU test loads from
automotive bulbs, especially old sealed beam headlamps, or they string
together a bunch of 5-10 watt resistors of equal resistance value in
series or parallel until they get the right amps and watts (BTW,
operate resistors at no more than half their rated wattage or they'll
get hot enough to melt plastic, burn fabric and wood, maybe even start
fires).

micky wrote:
On Sat, 9 Jul 2011 01:48:42 -0700 (PDT), "larry moe 'n curly"
wrote:


micky wrote:
Finally I found one from the first friend that was still in the
wrapping bag. Also a Silencer, Brand new, and 275 watts.

I tested it and the votlages were all good except the 12 volt pins
were actually a little lower than the one I removed!!!
Some PSUs, especially old ones like that and the newer high efficiency
designs, don't regulate their voltages very well at light loads and
may require draws of several amps before they work right. For
example, I have some high quality 12-year-old 300W Delta PSUs that I
can't use with low power computers because the +12V rail won't put out
enough voltage to make hard drives spin, unless the +5V rail is loaded
down with at least 3-4 amps. IOW measure voltages under realistic
loads.

Amazing, at least to me. Thanks.

As to my not connecting anything but the mother board, not the other
outputs too, surely the floppies and the CD drives use almost nothing
when they are not in use. The hard drive would use somet. Do
computers with cheap power supplies have a hard time displaying the
entire POST or the Setup/BIOS screens if there is no harddrive?

Or are the fans enough?


You might want something around 12V @ 1A load, and fans might draw
around 0.5A. Your motherboard doesn't power the processor from +12V
(most likely), so your +12V rail might only have fans on it.

Hard drives are a reasonably light load. The motor uses +12V, and
the current could be between 0.3A to 0.6A or so (idling). A couple hard
drives, with data cable disconnected, might serve as a load. Hard
drives can draw up to 2.5 amps during spinup, for the first ten
seconds, so the loading isn't constant as such. The power supply
has to supply more current, right after you turn on the circuit.
After ten seconds, the spindles are up to speed on the drives,
and the current flow level drops back to 0.3A to 0.6A on
each drive.

When testing power supplies of unknown quality, you don't
use your "good" hard drives :-) That's the problem with
using hard drives, is what happens if the power supply 12V
rail is running at 15V.

If your ATX supply had a 12V @ 15A rating, and you connected
two hard drives, the hard drives will draw up to 5A for the
first ten seconds, settling down to 1.2A or less, once up to
speed. If you use too many hard drives, you could violate
the rating, due to the spinup current draw. In this example,
six hard drives would be "max" (as then, you'd be drawing
15A for the first ten seconds).

Hard drives are convenient as a load, since the connector
is ready to go, and easily mates with the ATX supply. As long
as you're aware of the spinup current, and don't use
too many, it makes a fine source of loading.

*******

I use power resistors from an electronics store, for test loads,
and those can be used for test purposes. This is an example
of what you can find for resistors. These particular ones have
a metal body, and can handle 25W or 50W. The 50W ones are
a bit bigger. And power resistors get good and hot. On my
load box, I use an 80mm fan for cooling, across the resistors.
There is material between the metal body and the wire wound resistor
inside, so the metal should not be electrified.

http://www.galco.com/techdoc/nte/25wm220_cp.pdf

The 25WM012 is a 12 ohm resistor. If connected across the 12V
rail, the current draw is 12V / 12 ohms = 1 amp. The power
dissipated, is 12V * 1A = 12 watts. And 12 watts, in such a
small package, should have some cool air across it. If you
were only dumping a couple watts, it might be sufficient to
convection cool it.

You adjust the ohms of the one you purchase, to get the
loading you desire. If you used a 3 ohm resistor,
12V / 3ohm = 4 amps. And 12V * 4A = 48W, and that 50W resistor
is cooking. The 25W resistor is probably in serious trouble.
You can use combinations of resistors, in series or in
parallel, to help spread out the heating. I don't generally
set up my load box resistors, to get near their name plate
rating in watts. I try to keep the watts within reason,
using a fraction of the watt rating so the surface
temperature won't be too high.

Some ceramic resistors, can operate at 300C, in which
case, you don't need the fan, but don't touch it :-)
The 25WM012 above can take 275C, but I probably wouldn't
push that one that hard. I have some wirewound ceramic
power resistors, and you can tell by looking at them,
they'll take a lot of heat.

Generally speaking, light bulbs are not recommended as test
loads, at least when power is tightly constrained. To
give an example, I bought a DC adapter (wall wart) at the store,
something like 12V @ 2A, connected an automotive light bulb,
perhaps 12V @ 1A, and it causes the DC adapter to shut off.
The bulb would not light. So I can't test that adapter with the bulb
as a load. The reason for this, is when the automotive light
bulb is cold, the initial current draw can be double or more,
the "running" current flow level. When the filament is hot,
that is when it draws 1A. My DC adapter, being a switcher,
detects the overload instantly, and won't allow the cold
filament overload to last for more than a fraction of a second.
More crude power technologies, don't react immediately like that,
which is why they might allow the bulb to warm enough not to continue
to be an overload. Switching supplies can be set up, to shut off
very quickly, before the bulb even gets warm.

So in some ways, the "bad habits" of the disk drive
(the 2.5A spinup current), are mirrored in the operation
of the automotive light bulb (fraction of a second, cold
filament current flow). As long as you're aware of
the electrical characteristics of the initial inrush,
you can figure out a safe number of loads to use.

If the ATX supply had a 12V @ 15A rating, and you connect a
12V @ 1A automotive light bulb, no problem. The initial
cold filament surge current will be handled with ease.
But if the total loading of light bulbs, say eight light bulbs
in parallel, is slightly over half the supply ampere rating,
there is a chance the supply would "turn off on overload",
due to the initial cold filament surge. This is one reason,
I use real power resistors, because while they do have a
temperature coefficient, it isn't nearly as non-linear as a
light bulb.

There are metals with a pretty low temperature coefficient of
electrical resistance, such as manganin and related alloys.
The resistor used inside a multimeter, when making current
flow measurements, will have a low temperature coefficient,
and the resistance value won't change much at all when it
gets warm. By comparison, my load box would be inferior to
one of those. But using the automotive light bulb, as a
current shunt inside the multimeter, while cheap, would
throw any measurements out the window (50% error plus).
You use this stuff, for utmost accuracy, when the resistance
must remain stable. For best results, this stuff has to
be handled with care, annealed and the like.

http://en.wikipedia.org/wiki/Manganin

http://www.o-digital.com/uploads/217...n_Shunt_42.jpg

You wouldn't waste that stuff for making load resistors, as
it would be too expensive.

So those are examples of some loads and resistor types.
Since you have hard drives on hand, those are the
closest thing within reach, to draw a bit of current.

Paul