These LED replacements for 240V mains lamps; if one were to
open them, would one find a high voltage regulator suitable for
some of our valve experiments and repairs?

gareth wrote:
These LED replacements for 240V mains lamps; if one were to
open them, would one find a high voltage regulator suitable for
some of our valve experiments and repairs?

You might find a little constant current supply, but my guess is that
you'd just find a big dropping resistor. That configuration would
result in most of the power being wasted as heat, but it would still
produce less heat than an incandescent and be brighter.

If you want a high voltage regulator, a TIP50 transistor and a high
voltage zener (or a string of low voltage zeners) will fix you right
up. The TIP50 is comparatively easy to damage, but if you don't hook
it up backwards or something it will be very, very reliable. Not
expensive.

Think of the TIP50 as a 5080 replacement with a lot more gain and
better transconductance in the bargain.

If you want a high voltage switcher, on the other hand, look at the
Linear Technology chips intended for LCD backlight inverters. There
are some great Jim Williams applications notes.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 11/28/2014 8:50 AM, Scott Dorsey wrote:
gareth wrote:
These LED replacements for 240V mains lamps; if one were to
open them, would one find a high voltage regulator suitable for
some of our valve experiments and repairs?

You might find a little constant current supply, but my guess is that
you'd just find a big dropping resistor. That configuration would
result in most of the power being wasted as heat, but it would still
produce less heat than an incandescent and be brighter.

If you want a high voltage regulator, a TIP50 transistor and a high
voltage zener (or a string of low voltage zeners) will fix you right
up. The TIP50 is comparatively easy to damage, but if you don't hook
it up backwards or something it will be very, very reliable. Not
expensive.

Think of the TIP50 as a 5080 replacement with a lot more gain and
better transconductance in the bargain.

If you want a high voltage switcher, on the other hand, look at the
Linear Technology chips intended for LCD backlight inverters. There
are some great Jim Williams applications notes.
--scott


No, these have electronic power supplies in them. Otherwise they would
dissipate huge amounts of heat. Think about it. LED's run at about 3V.
That means a 9W LED requires about 3 amps of power. 3 amps at 240V is
720W - or about 711W of power wasted. They would be way less efficient
than any other type of bulbs. Plus LED's run on DC and would not work
as efficiently on 50Hz AC.

However, they also are generally pretty well potted and almost
impossible to take apart without destroying them. And even if you could
get one apart, its design is single-purpose and generally won't do well
in a different application.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

Jerry Stuckle wrote:
No, these have electronic power supplies in them. Otherwise they would
dissipate huge amounts of heat. Think about it. LED's run at about 3V.
That means a 9W LED requires about 3 amps of power. 3 amps at 240V is
720W - or about 711W of power wasted. They would be way less efficient
than any other type of bulbs. Plus LED's run on DC and would not work
as efficiently on 50Hz AC.

9W is an enormous amount of power for an LED. The LEDs used to replace
pilot lamps are normally running 10mA, not 3 amps. This is what allows
a dropping resistor to be used.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 11/28/2014 11:11 PM, Scott Dorsey wrote:
Jerry Stuckle wrote:
No, these have electronic power supplies in them. Otherwise they would
dissipate huge amounts of heat. Think about it. LED's run at about 3V.
That means a 9W LED requires about 3 amps of power. 3 amps at 240V is
720W - or about 711W of power wasted. They would be way less efficient
than any other type of bulbs. Plus LED's run on DC and would not work
as efficiently on 50Hz AC.

9W is an enormous amount of power for an LED. The LEDs used to replace
pilot lamps are normally running 10mA, not 3 amps. This is what allows
a dropping resistor to be used.
--scott



You are confusing LEDs with LED bulbs. A 9W LED bulb is equivalent to
about a 60W incandescent bulb.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

Jerry Stuckle wrote:
On 11/28/2014 11:11 PM, Scott Dorsey wrote:
Jerry Stuckle wrote:
No, these have electronic power supplies in them. Otherwise they would
dissipate huge amounts of heat. Think about it. LED's run at about 3V.
That means a 9W LED requires about 3 amps of power. 3 amps at 240V is
720W - or about 711W of power wasted. They would be way less efficient
than any other type of bulbs. Plus LED's run on DC and would not work
as efficiently on 50Hz AC.

9W is an enormous amount of power for an LED. The LEDs used to replace
pilot lamps are normally running 10mA, not 3 amps. This is what allows
a dropping resistor to be used.


You are confusing LEDs with LED bulbs. A 9W LED bulb is equivalent to
about a 60W incandescent bulb.

Ahh, I thought you were talking about the high intensity LED replacements
for incandescent pilot lamps. Not the household bulb replacements. The
house lamp replacements have switchers in them.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Fri, 28 Nov 2014 08:50:09 -0500, Scott Dorsey wrote:

gareth wrote:
These LED replacements for 240V mains lamps; if one were to open them,
would one find a high voltage regulator suitable for some of our valve
experiments and repairs?

You might find a little constant current supply, but my guess is that
you'd just find a big dropping resistor. That configuration would
result in most of the power being wasted as heat, but it would still
produce less heat than an incandescent and be brighter.

If you want a high voltage regulator, a TIP50 transistor and a high
voltage zener (or a string of low voltage zeners) will fix you right up.
The TIP50 is comparatively easy to damage, but if you don't hook it up
backwards or something it will be very, very reliable. Not expensive.

Think of the TIP50 as a 5080 replacement with a lot more gain and better
transconductance in the bargain.

If you want a high voltage switcher, on the other hand, look at the
Linear Technology chips intended for LCD backlight inverters. There are
some great Jim Williams applications notes.
--scott

The regulators in LED lamps are constant current types, not constant
voltage. They also have some sort of step-down circuit because the LED
needs a lot more current than what you would want to draw from the AC
lines. Common power LED currents are in the neighborhood of 350 and 700
mA.

Some very small LED lamps, Christmas light size, use capacitors to limit
the current.

Jim Mueller



--
Jim Mueller

To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.

In rec.radio.amateur.boatanchors gareth wrote:
These LED replacements for 240V mains lamps; if one were to
open them, would one find a high voltage regulator suitable for
some of our valve experiments and repairs?

As the regulators are potted in and would be difficult to remove, and
since LED's run on voltages on the order of 2-3 volts, no.

How many 3 volt valves can you name?



--
Jim Pennino

On Fri, 28 Nov 2014, wrote:

In rec.radio.amateur.boatanchors gareth wrote:
These LED replacements for 240V mains lamps; if one were to
open them, would one find a high voltage regulator suitable for
some of our valve experiments and repairs?

As the regulators are potted in and would be difficult to remove, and
since LED's run on voltages on the order of 2-3 volts, no.

How many 3 volt valves can you name?

I think that point was that if a regulator was used to drop the line
voltage to those 3volts, it could handle high voltage input. The probably
false assumption is that the regulator would be variable from some very
high output voltage to some very low output voltage, so one could use it
for tubes by making that adjustment.

A lot of IC regulators can't handle high voltage. If nothing else, nobody
saw the need, it was the solid state age. So dissipation issues aside,
most regulators expect at most a relatively low DC voltage input.

Of course, one can run tubes on low voltage. The Collins 75S receiver
line apparently kept plat voltage relatively low (somewhere around 120v if
I remember right) which had certain advantages. One can run regular tubes
at 12VDC on the plate, there were some articles in Popular Electronics
about this, calling them "starved circuits". Or there were those tubes
designed to run off 12VDC for those hybrid car radios, a last gasp before
transistors took over completely.

Though, 3VDC does seem a tad low.

Michael

In rec.radio.amateur.boatanchors Michael Black wrote:
On Fri, 28 Nov 2014, wrote:

In rec.radio.amateur.boatanchors gareth wrote:
These LED replacements for 240V mains lamps; if one were to
open them, would one find a high voltage regulator suitable for
some of our valve experiments and repairs?

As the regulators are potted in and would be difficult to remove, and
since LED's run on voltages on the order of 2-3 volts, no.

How many 3 volt valves can you name?

I think that point was that if a regulator was used to drop the line
voltage to those 3volts, it could handle high voltage input. The probably
false assumption is that the regulator would be variable from some very
high output voltage to some very low output voltage, so one could use it
for tubes by making that adjustment.

Given that manufacturers want the least cost in a product, and the
regulator in a light bulb would have no need for a variable regulator,
and that these things are made in the millions, it would be extremely
silly to assume that the regulator is anything other than a fixed
regulator for LED's and is designed to handle the load of some fixed
number of LED's.

A lot of IC regulators can't handle high voltage. If nothing else, nobody
saw the need, it was the solid state age. So dissipation issues aside,
most regulators expect at most a relatively low DC voltage input.

True for IC regulators. Hoever high voltage transistors exist these
days which makes designing a high voltage regulator pretty trivial.

Of course, one can run tubes on low voltage. The Collins 75S receiver
line apparently kept plat voltage relatively low (somewhere around 120v if
I remember right) which had certain advantages. One can run regular tubes
at 12VDC on the plate, there were some articles in Popular Electronics
about this, calling them "starved circuits". Or there were those tubes
designed to run off 12VDC for those hybrid car radios, a last gasp before
transistors took over completely.

Though, 3VDC does seem a tad low.

When they were running regular tubes on "low voltage", that was voltages
around 100 V as opposed to 200 to 300 Volts.

The 12 Volt tubes are long gone and not that great to begin with.

Michael

--
Jim Pennino