What is better, old-fashioned transformer or new-fangled "SWITCHINGAC TO DC POWER SUPPLY"

The former is a heavy cube, has PCB oil and nasty chemicals sealed inside it, with copper turns according to how much you want to step down / step up the voltage, forms a natural kind of surge suppressor, lasts forever and is expensive.

The latter is the opposite, but the 'modern' trend.

Obviously in this day and age of disposable electronics the latter is 'better' for the environment and more cost effective, but they do seem (based on anecdotal evidence) to 'go bad' more often, such as during electrical storms or so it seems.

RL

On Wednesday, July 11, 2012 10:51:30 PM UTC-4, RayLopez99 wrote:
The former is a heavy cube, has PCB oil and nasty chemicals sealed inside it, with copper turns according to how much you want to step down / step up the voltage, forms a natural kind of surge suppressor, lasts forever and is expensive.

The latter is the opposite, but the 'modern' trend.


RL

Also the old-fashioned transformer gets a lot hotter and stays hot (I think it's a 'passive' system that just is always on) while the modern kind is usually cool to the touch.

RL

"RayLopez99" wrote in message
...

The former is a heavy cube, has PCB oil and nasty chemicals sealed inside
it, with copper turns according to how much you want to step down / step up
the voltage, forms a natural kind of surge suppressor, lasts forever and is
expensive.

The latter is the opposite, but the 'modern' trend.

Obviously in this day and age of disposable electronics the latter is
'better' for the environment and more cost effective, but they do seem
(based on anecdotal evidence) to 'go bad' more often, such as during
electrical storms or so it seems.

RL

The transformers used in small consumer equipment does not have PCB oil and
chemicals inside, They are mainly soft iron cores and copper wire with
various turns to supply the required volts and amps.

Regards , Rene

RayLopez99 wrote:


Also the old-fashioned transformer gets a lot hotter and stays hot
(I think it's a 'passive' system that just is always on) while the modern
kind is usually cool to the touch.

RL

Actually, there is a cure for that. Hammond (a transformer maker), makes
a toroidal mains transformer. Which it claims is a lot more efficient,
and produces very little heat. There's only one problem with it, and
that is it has a bit of an inrush problem when first turned on. So
you shouldn't use it in its most basic form, without additional
components to feed it. Other than that, it solves the waste heat
problem.

What I've noticed about lamination-based transformers, is they can become
warmer with age. If the laminations start to rust, and the rust punches through the
lacquer applied to the laminations, a higher level of eddy current can flow.
I have a transformer here, that needs to be replaced for that reason
(it will overheat on its own after an hour of operation), and it was
sold by RadioShack (surprise! :-) ).

I have some other transformers, that have lasted for years, and are
still cool to the touch. So on those, the eddy currents haven't changed
at all. If you have a transformer running hot, it could very well
be effectively failed, and out of spec.

Paul

On Jul 11, 10:51 pm, RayLopez99 wrote:
The former is a heavy cube, has PCB oil and nasty chemicals sealed inside it, with copper turns according to how much you want to step down / step up the voltage, forms a natural kind of surge suppressor, lasts forever and is expensive.

The latter is the opposite, but the 'modern' trend.

Obviously in this day and age of disposable electronics the latter is 'better' for the environment and more cost effective, but they do seem (based on anecdotal evidence) to 'go bad' more often, such as during electrical storms or so it seems.

RL

That's right. Nobody really needs point-to-point Class A amplifiers
with heavy-iron transformers for driving 6L6 or KT88 valve-based
output wattage off second-order harmonics. Send them donated all to
me and I'll be sure they're ecologically well care for.

On Thursday, July 12, 2012 12:51:30 PM UTC+10, RayLopez99 wrote:
The former is a heavy cube, has PCB oil and nasty chemicals sealed inside it, with copper turns according to how much you want to step down / step up the voltage, forms a natural kind of surge suppressor, lasts forever and is expensive.


I think you will find that only old pole transformers had the PCB oil in them, however it is enclosed inside the transformer, and it is not dangerous as long as the case is not ruptured - allowing the oil to escape and contact someone

The reliabilty is very very high, decades for many of them, depending on how
well they are made.



The latter is the opposite, but the 'modern' trend.

Obviously in this day and age of disposable electronics the latter is 'better' for the environment and more cost effective, but they do seem (based on anecdotal evidence) to 'go bad' more often, such as during electrical storms or so it seems.

RL


They do, but they still use a transformer - (running at a much higher frequency than the 50Hz Mains, allowing the transformer to be much smaller and run cooler) in their operation (or possibly an inductor, if isolation is not required). These can be reliable if made properly (we recently decommissioned some "Panasonic" 200w switching PC supplies from circa 1985, as well as some 1983 "wang" units that were lower wattage, and had nil failure rates until the last 3 years)

Usually though, these are less reliable, but not too bad.


The oldest linear power supply I have here, and have just kept as a momento - is a 1972 STC computer power supply, that would be about 200w, has 2 120mm fans internally, weighs about 80lb, and is as big as a typical mid size PC tower. External fans are also required to be installed in the case (19" rack) it is housed in, and must actually be plugged into a mains socket on the power supply, before it is able to be switched on.

At least with linear you don't have the problem of your AC line getting
clipped.

I had a linear supply on a computer (pre PC days) that continually
rebooted. Seems that the switching supplies in the display copiers
(dealer showroom) pulled enough off the peaks of the supplied power line
that the linear couldn't get enough. Scoped the power line and the
normal AC had probably the top 10% flat-topped.
A separate dedicated line resolved it.

On Mon, 16 Jul 2012, edfair wrote:

At least with linear you don't have the problem of your AC line getting
clipped.

I had a linear supply on a computer (pre PC days) that continually
rebooted. Seems that the switching supplies in the display copiers
(dealer showroom) pulled enough off the peaks of the supplied power line
that the linear couldn't get enough. Scoped the power line and the
normal AC had probably the top 10% flat-topped.
A separate dedicated line resolved it.

Of course, in those days a linear power supply may have been just "good
enough" due to the cost of a larger transformer. So when you added more
cards, and you'd need more cards to do much, the power supply wasn't good
enough.

Or, to keep heat down from power lost in the regulators, the transformer
put out the bare minimum needed by the regulators, and if the power line
voltage dropped, suddenly there goes the power supply since the regulators
were no longer getting enough voltage.

Switching supplies can control the voltage on the power line side of
things, so variations like this can be worked around.

Michael