I have a desk lamp, with a magnifier and a 12W T4 circline fluorescent bulb,
that I use constantly for working on PCBs and electronics projects in
general. I bought it several years ago and recently it started flickering
and then died. I replaced the bulb, but still no joy, and after replacing
the blown fuse and two damaged transistors, I found that the little
transformer had an open winding.

So, I thought, a 60W equivalent CFL is actually about 11-13 watts, and the
little circuit in them should work. I had a couple of broken or dead bulbs
ready for recycling, so I opened the bases, cut the leads, and extracted the
PCBs. After a few unsuccessful tries, I was able to get it to work and now
my lamp is once again operational.

I found some schematics of the CFL driver boards he
http://www.pavouk.org/hw/lamp/en_index.html

Some of those circuits matched what I had almost exactly. It was a little
difficult to follow the explanation of how they operate, but what was
confusing is the four pins shown on the lamp itself, which is also how the
bulbs are made. I assume they are the heaters that are usually activated
with a starter, but I did not find any continuity on those pins. The desk
lamp only had one wire to each of two pins on the circline bulb, but in the
CFLs all four wires were connected to different points on the PCB. It would
only work when I shorted the connections that would have gone to the
heaters, and it seems to work very well. It starts to light at 50 VAC and
reaches full brightness at 100-120V, at which it draws about 100mA. That's
close enough to 12 watts for me!

Here's a little clip of my repair project:
http://www.youtube.com/watch?v=e7QJQ...ature=youtu.be

This is good to know. Those little circuits in each CFL have a lot of good
components, including a DIAC and high voltage transistors, and it's probably
possible to use them to drive small fluorescent lamps for DIY projects or
repair. I doubt they could be used for the 40W tubes, but a driver from a
100W CFL should work on a 20W tube such as are in many desk lamps and small
kitchen fixtures.

Does anyone know if there is any problem with this?

Thanks,

Paul

PS: GO RAVENS!!!!!

P E Schoen wrote in message
...
I have a desk lamp, with a magnifier and a 12W T4 circline fluorescent bulb,
that I use constantly for working on PCBs and electronics projects in
general. I bought it several years ago and recently it started flickering
and then died. I replaced the bulb, but still no joy, and after replacing
the blown fuse and two damaged transistors, I found that the little
transformer had an open winding.

So, I thought, a 60W equivalent CFL is actually about 11-13 watts, and the
little circuit in them should work. I had a couple of broken or dead bulbs
ready for recycling, so I opened the bases, cut the leads, and extracted the
PCBs. After a few unsuccessful tries, I was able to get it to work and now
my lamp is once again operational.

I found some schematics of the CFL driver boards he
http://www.pavouk.org/hw/lamp/en_index.html

Some of those circuits matched what I had almost exactly. It was a little
difficult to follow the explanation of how they operate, but what was
confusing is the four pins shown on the lamp itself, which is also how the
bulbs are made. I assume they are the heaters that are usually activated
with a starter, but I did not find any continuity on those pins. The desk
lamp only had one wire to each of two pins on the circline bulb, but in the
CFLs all four wires were connected to different points on the PCB. It would
only work when I shorted the connections that would have gone to the
heaters, and it seems to work very well. It starts to light at 50 VAC and
reaches full brightness at 100-120V, at which it draws about 100mA. That's
close enough to 12 watts for me!

Here's a little clip of my repair project:
http://www.youtube.com/watch?v=e7QJQ...ature=youtu.be

This is good to know. Those little circuits in each CFL have a lot of good
components, including a DIAC and high voltage transistors, and it's probably
possible to use them to drive small fluorescent lamps for DIY projects or
repair. I doubt they could be used for the 40W tubes, but a driver from a
100W CFL should work on a 20W tube such as are in many desk lamps and small
kitchen fixtures.

Does anyone know if there is any problem with this?

Thanks,

Paul

PS: GO RAVENS!!!!!


+++++++++

so the original lamp was conventional ballast and 2 pin bimetal switch
starter ?

Besides the electrolytic and bulb, the starter cap is very failure-prone.
In circuits where the filaments are used, it's in series with the output,
forming a series resonant tank; the low resistance of the cold filaments
draws lots of current, starting the tube quickly. When the tube starts
up, it appears in parallel with the cap, transforming the circuit into a
good old series inductance ballast.

The kind with only two pins skips the heating step and allows the tank
voltage and current to resonate even higher, until the tube breaks down
cold-cathode style. Once ignited, ion bombardment keeps the filaments
warm, keeping the reignition and operating voltages normal.

High voltage film caps are big and expensive, so understandably, they
don't like to use them very much. Often, a poor green (polyester) type is
found, which isn't even green anymore, but black from the abuse. Others
may be burned through, having experienced too many starts (too much peak
voltage) that self-healing has burned away most of the capacitance. The
circuit then either tries oscillating too high (burning itself from
switching loss) or oscillates lazily or latches (resonance no longer
strong enough to draw enough current to provide sufficient feedback).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://seventransistorlabs.com

"P E Schoen" wrote in message
...
I have a desk lamp, with a magnifier and a 12W T4 circline fluorescent
bulb,
that I use constantly for working on PCBs and electronics projects in
general. I bought it several years ago and recently it started flickering
and then died. I replaced the bulb, but still no joy, and after replacing
the blown fuse and two damaged transistors, I found that the little
transformer had an open winding.

So, I thought, a 60W equivalent CFL is actually about 11-13 watts, and the
little circuit in them should work. I had a couple of broken or dead bulbs
ready for recycling, so I opened the bases, cut the leads, and extracted
the
PCBs. After a few unsuccessful tries, I was able to get it to work and now
my lamp is once again operational.

I found some schematics of the CFL driver boards he
http://www.pavouk.org/hw/lamp/en_index.html

Some of those circuits matched what I had almost exactly. It was a little
difficult to follow the explanation of how they operate, but what was
confusing is the four pins shown on the lamp itself, which is also how the
bulbs are made. I assume they are the heaters that are usually activated
with a starter, but I did not find any continuity on those pins. The desk
lamp only had one wire to each of two pins on the circline bulb, but in
the
CFLs all four wires were connected to different points on the PCB. It
would
only work when I shorted the connections that would have gone to the
heaters, and it seems to work very well. It starts to light at 50 VAC and
reaches full brightness at 100-120V, at which it draws about 100mA. That's
close enough to 12 watts for me!

Here's a little clip of my repair project:
http://www.youtube.com/watch?v=e7QJQ...ature=youtu.be

This is good to know. Those little circuits in each CFL have a lot of good
components, including a DIAC and high voltage transistors, and it's
probably
possible to use them to drive small fluorescent lamps for DIY projects or
repair. I doubt they could be used for the 40W tubes, but a driver from a
100W CFL should work on a 20W tube such as are in many desk lamps and
small
kitchen fixtures.

Does anyone know if there is any problem with this?

Thanks,

Paul

PS: GO RAVENS!!!!!

On Jan 21, 8:43*am, "Tim Williams" wrote:
Besides the electrolytic and bulb, the starter cap is very failure-prone.

FWIW, of the modest pile of CFLs I autopsied from my own house, 100%
of the failures were from failed heaters.

This may be atypical. I get good service from CFLs running them
without enclosures; the enclosed, base-up fail modes may be different.

--
Cheers,
James Arthur

wrote in message
...
On Jan 21, 8:43 am, "Tim Williams" wrote:
Besides the electrolytic and bulb, the starter cap is very failure-prone.

FWIW, of the modest pile of CFLs I autopsied from my own house, 100%
of the failures were from failed heaters.

This may be atypical. I get good service from CFLs running them
without enclosures; the enclosed, base-up fail modes may be different.

--
Cheers,
James Arthur

And frequent cycling on/off is the major failure mechanism of the heaters,
IMHO. I get very good life from CFL's in constant-on service. The Bright
Effects lamps from Lowe's have been very good, and are priced fairly.
Tom

FWIW, of the modest pile of CFLs I autopsied from my own house, 100%
of the failures were from failed heaters.

** Most CFLs have PTC thermistors that increase current flow to the heater
for the first few seconds - makes the lamp start quickly, particularly in
cool weather conditions.

It also burns out the heater in a few hundred or so cycles.

Claims for life spans of 6 or 8 thousand hours are based on continuous use
in a cool environment - plus lotsa good luck.


This may be atypical. I get good service from CFLs running them
without enclosures; the enclosed, base-up fail modes may be different.


** Recently, a neighbour had an 18W CFL explode and bits go all over the
kitchen - it was base up in a non ventilated fitting.


.... Phil

Most CFLs have PTC thermistors that increase current flow
to the heater for the first few seconds - makes the lamp start
quickly, particularly in cool weather conditions.
It also burns out the heater in a few hundred or so cycles.

Fortunately, I have not had this problem. The CFLs in my bathroom and bedroom
have lasted two to three years, and are turned on and off several times a day.

On Tue, 22 Jan 2013 06:40:44 -0800, "William Sommerwerck"
wrote:

Most CFLs have PTC thermistors that increase current flow
to the heater for the first few seconds - makes the lamp start
quickly, particularly in cool weather conditions.
It also burns out the heater in a few hundred or so cycles.

Fortunately, I have not had this problem. The CFLs in my bathroom and bedroom
have lasted two to three years, and are turned on and off several times a day.

Two or three years? I have incandescents that last a lot longer than
that.

"Phil Allison" wrote in message
...



FWIW, of the modest pile of CFLs I autopsied from my own house, 100%
of the failures were from failed heaters.

** Most CFLs have PTC thermistors that increase current flow to the heater
for the first few seconds - makes the lamp start quickly, particularly in
cool weather conditions.

It also burns out the heater in a few hundred or so cycles.

Claims for life spans of 6 or 8 thousand hours are based on continuous use
in a cool environment - plus lotsa good luck.


This may be atypical. I get good service from CFLs running them
without enclosures; the enclosed, base-up fail modes may be different.


** Recently, a neighbour had an 18W CFL explode and bits go all over the
kitchen - it was base up in a non ventilated fitting.

Must've been a pretty big explosion for bits to go everywhere from a
non-ventilated fitting!

On Tue, 22 Jan 2013 16:44:06 -0000, "Ian Field"
wrote:



"Phil Allison" wrote in message
...



FWIW, of the modest pile of CFLs I autopsied from my own house, 100%
of the failures were from failed heaters.

** Most CFLs have PTC thermistors that increase current flow to the heater
for the first few seconds - makes the lamp start quickly, particularly in
cool weather conditions.

It also burns out the heater in a few hundred or so cycles.

Claims for life spans of 6 or 8 thousand hours are based on continuous use
in a cool environment - plus lotsa good luck.


This may be atypical. I get good service from CFLs running them
without enclosures; the enclosed, base-up fail modes may be different.


** Recently, a neighbour had an 18W CFL explode and bits go all over the
kitchen - it was base up in a non ventilated fitting.

Must've been a pretty big explosion for bits to go everywhere from a
non-ventilated fitting!

Can lights aren't ventilated. In fact, many are insulated (IC rated).
They're hell on CFLs.

"Ian Field"
"Phil Allison"


FWIW, of the modest pile of CFLs I autopsied from my own house, 100%
of the failures were from failed heaters.

** Most CFLs have PTC thermistors that increase current flow to the
heater for the first few seconds - makes the lamp start quickly,
particularly in cool weather conditions.

It also burns out the heater in a few hundred or so cycles.

Claims for life spans of 6 or 8 thousand hours are based on continuous
use in a cool environment - plus lotsa good luck.


This may be atypical. I get good service from CFLs running them
without enclosures; the enclosed, base-up fail modes may be different.


** Recently, a neighbour had an 18W CFL explode and bits go all over the
kitchen - it was base up in a non ventilated fitting.

Must've been a pretty big explosion for bits to go everywhere from a
non-ventilated fitting!

** See the second half of this page for pics of the actual CFL and fitting.

http://sound.westhost.com/articles/il-cfl-6.htm

The are no ventilation a holes at the back of the fitting and all the spiral
CFLs were a neat fit.



.... Phil

wrote in message
...
On Jan 21, 8:43 am, "Tim Williams" wrote:
Besides the electrolytic and bulb, the starter cap is very
failure-prone.

FWIW, of the modest pile of CFLs I autopsied from my own house, 100%
of the failures were from failed heaters.

This may be atypical. I get good service from CFLs running them
without enclosures; the enclosed, base-up fail modes may be different.

I don't know if any do fail specifically due to the start cap -- as you
note, the filament tends to fail first. I haven't measured any of the
caps to see the capacitance loss, but the color change is reason enough.

EPCOS makes capacitors specifically for this service; their graphs of peak
voltage vs. capacitance are reminiscient of the Write-Only Memory's
"insertions vs. pins remaining" graph. ;-o

Base-up tends to cook the capacitor; better ones don't mind so much. My
parents have a GE "long life" model on their front porch, an enclosed
(vented enough that bugs find their way in, but not so much that they find
their way out before dying and making a pile...), base-up fixture.

I installed them something like four years ago; the other outdoor lights
(upright, even) have since failed, but the front porch, surprisingly,
still works.

I think. Come to think of it, I didn't look closely last time I was by;
the front porch may've been replaced, most likely under pressure, the
other "low priority targets" simply being "left in the dark"... :-)

Tim

--
Deep Friar: a very philosophical monk.
Website: http://seventransistorlabs.com

"Tim Williams" wrote in message
...
wrote in message
...
On Jan 21, 8:43 am, "Tim Williams" wrote:
Besides the electrolytic and bulb, the starter cap is very
failure-prone.

FWIW, of the modest pile of CFLs I autopsied from my own house, 100%
of the failures were from failed heaters.

This may be atypical. I get good service from CFLs running them
without enclosures; the enclosed, base-up fail modes may be different.

I don't know if any do fail specifically due to the start cap -- as you
note, the filament tends to fail first. I haven't measured any of the
caps to see the capacitance loss, but the color change is reason enough.

On the last CFL I autopsied; the electrolytic read a realistic ESR on the
Peak Atlas ESR70, but zero capacitance.

When I double checked with the DSE ESR meter it showed O/C.

On closer inspection, there was a tiny ring of corrosion "fur" round one of
the legs.

wrote in message
...

FWIW, of the modest pile of CFLs I autopsied from my own house,
100% of the failures were from failed heaters.

This may be atypical. I get good service from CFLs running them
without enclosures; the enclosed, base-up fail modes may be different.

I measured the heaters on one of the new circline lamps and they appear to
be about 3 ohms each. So in series, using a starter, they would draw a high
current surge and then probably much lower as they become nearly
incandescent. Of course the ballast would limit the current to some much
lower value. I figure that an ordinary magnetic ballast for 12W would drop
about 30 volts at 100 mA during normal operation, so probably about 400 mA
into the heaters.

But since this lamp had only two wire zipcord going from the electronic
ballast to the lamp, it obviously did not use the heaters with the original
circuit. So I just shorted the connections for the heaters at the board, and
it works perfectly well. I can't see where the 6 ohms of filament resistance
would make much difference to a circuit designed for 100 mA, and I don't
know why the CFLs use the heaters at all, or why they should burn out. It
does appear that the heaters of the one dead CFL are open, although I
thought I had continuity through one when I first measured it. One of the
CFLs actually got broken when I hit it with a flyswatter as I waged war on
the stinkbugs that love to circle the lamp. It seemed to continue to glow
for a while, which may have been the heaters.

The defunct circline lamp shows discoloration on one end and that heater is
open, while the other is OK. I don't know how it can burn out if there is
only one wire connected to it. Perhaps it just vaporizes because of the
current flowing from it into the fluorescent plasma? I don't really know the
details of operation.

When I was still in High School I made a little multivibrator circuit that
fed a 12V transformer and I connected the 120V winding through a capacitor
to a small fluorescent lamp in a camping lantern. It originally used a big
high voltage battery (maybe 90 volts and maybe two of them), and maybe some
sort of vibrator as in old tube type car radios to get the AC voltage for
the lamp. Will it work on just DC? My conversion worked on a 12V motorcycle
battery, and it was instant start, whereas the original had a starter
button. I think I still have that lantern somewhere. I should find it and
look inside.

I also have an old lantern that originally used two big doorbell batteries
(remember them?), and I replaced them with a NiCad battery that was made of
plexiglass so you could see the plates and electrolyte inside and possibly
even service it. My father worked for a company that made exotic batteries
for the military and I think this came from there, probably 50 years ago.

Paul

On Mon, 21 Jan 2013 04:04:24 -0500, "P E Schoen" wrote:

I have a desk lamp, with a magnifier and a 12W T4 circline fluorescent bulb,
that I use constantly for working on PCBs and electronics projects in
general. I bought it several years ago and recently it started flickering
and then died. I replaced the bulb, but still no joy, and after replacing
the blown fuse and two damaged transistors, I found that the little
transformer had an open winding.

So, I thought, a 60W equivalent CFL is actually about 11-13 watts, and the
little circuit in them should work. I had a couple of broken or dead bulbs
ready for recycling, so I opened the bases, cut the leads, and extracted the
PCBs. After a few unsuccessful tries, I was able to get it to work and now
my lamp is once again operational.

I found some schematics of the CFL driver boards he
http://www.pavouk.org/hw/lamp/en_index.html

Some of those circuits matched what I had almost exactly. It was a little
difficult to follow the explanation of how they operate, but what was
confusing is the four pins shown on the lamp itself, which is also how the
bulbs are made. I assume they are the heaters that are usually activated
with a starter, but I did not find any continuity on those pins. The desk
lamp only had one wire to each of two pins on the circline bulb, but in the
CFLs all four wires were connected to different points on the PCB. It would
only work when I shorted the connections that would have gone to the
heaters, and it seems to work very well. It starts to light at 50 VAC and
reaches full brightness at 100-120V, at which it draws about 100mA. That's
close enough to 12 watts for me!

Here's a little clip of my repair project:
http://www.youtube.com/watch?v=e7QJQ...ature=youtu.be

This is good to know. Those little circuits in each CFL have a lot of good
components, including a DIAC and high voltage transistors, and it's probably
possible to use them to drive small fluorescent lamps for DIY projects or
repair. I doubt they could be used for the 40W tubes, but a driver from a
100W CFL should work on a 20W tube such as are in many desk lamps and small
kitchen fixtures.

Does anyone know if there is any problem with this?

Thanks,

Paul

PS: GO RAVENS!!!!!


Problem? Yes. It would have been more sensible to replace that ancient, flakey,
mercury-filled toob with LEDs.

PS: GO NINERS!!!!!!!!!



--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

"P E Schoen" wrote in message
...
I have a desk lamp, with a magnifier and a 12W T4 circline fluorescent
bulb, that I use constantly for working on PCBs and electronics projects
in general. I bought it several years ago and recently it started
flickering and then died. I replaced the bulb, but still no joy, and after
replacing the blown fuse and two damaged transistors, I found that the
little transformer had an open winding.

So, I thought, a 60W equivalent CFL is actually about 11-13 watts, and the
little circuit in them should work. I had a couple of broken or dead bulbs
ready for recycling, so I opened the bases, cut the leads, and extracted
the PCBs. After a few unsuccessful tries, I was able to get it to work and
now my lamp is once again operational.

I found some schematics of the CFL driver boards he
http://www.pavouk.org/hw/lamp/en_index.html

Some of those circuits matched what I had almost exactly. It was a little
difficult to follow the explanation of how they operate, but what was
confusing is the four pins shown on the lamp itself, which is also how the
bulbs are made. I assume they are the heaters that are usually activated
with a starter, but I did not find any continuity on those pins. The desk
lamp only had one wire to each of two pins on the circline bulb, but in
the CFLs all four wires were connected to different points on the PCB. It
would only work when I shorted the connections that would have gone to the
heaters, and it seems to work very well. It starts to light at 50 VAC and
reaches full brightness at 100-120V, at which it draws about 100mA. That's
close enough to 12 watts for me!

Here's a little clip of my repair project:
http://www.youtube.com/watch?v=e7QJQ...ature=youtu.be


Many CFL PCBs have a diac - you can make a neat little pulsed bicycle light
using a blocking oscillator inverter to charge a 47u electro. Everytime it
reaches about 32V, you have the diac dump the charge into the LED bank of a
cheap & nasty LED worklight.

My project was published in Elektor a year or two ago.

"P E Schoen" schreef in bericht
...
I have a desk lamp, with a magnifier and a 12W T4 circline fluorescent bulb,
that I use constantly for working on PCBs and electronics projects in
general. I bought it several years ago and recently it started flickering
and then died. I replaced the bulb, but still no joy, and after replacing
the blown fuse and two damaged transistors, I found that the little
transformer had an open winding.

So, I thought, a 60W equivalent CFL is actually about 11-13 watts, and the
little circuit in them should work. I had a couple of broken or dead bulbs
ready for recycling, so I opened the bases, cut the leads, and extracted the
PCBs. After a few unsuccessful tries, I was able to get it to work and now
my lamp is once again operational.

I found some schematics of the CFL driver boards he
http://www.pavouk.org/hw/lamp/en_index.html

Some of those circuits matched what I had almost exactly. It was a little
difficult to follow the explanation of how they operate, but what was
confusing is the four pins shown on the lamp itself, which is also how the
bulbs are made. I assume they are the heaters that are usually activated
with a starter, but I did not find any continuity on those pins. The desk
lamp only had one wire to each of two pins on the circline bulb, but in the
CFLs all four wires were connected to different points on the PCB. It would
only work when I shorted the connections that would have gone to the
heaters, and it seems to work very well. It starts to light at 50 VAC and
reaches full brightness at 100-120V, at which it draws about 100mA. That's
close enough to 12 watts for me!

Here's a little clip of my repair project:
http://www.youtube.com/watch?v=e7QJQ...ature=youtu.be

This is good to know. Those little circuits in each CFL have a lot of good
components, including a DIAC and high voltage transistors, and it's probably
possible to use them to drive small fluorescent lamps for DIY projects or
repair. I doubt they could be used for the 40W tubes, but a driver from a
100W CFL should work on a 20W tube such as are in many desk lamps and small
kitchen fixtures.

Does anyone know if there is any problem with this?

Thanks,

Paul

PS: GO RAVENS!!!!!

The traditional way of igniting TLs is first heating the heaters and then
start it with a relative high voltage puls. But heating first is not
necessary. The lamp will ignite if only the voltage of the ignition pulse is
high enough. Nevertheless, the heaters cannot be omitted as they provide the
electrons required for the current through the tube. Especially low power
TLs are sometimes ignited this way. When used with low frequencies i.e. 50Hz
or 60Hz, it is said to shorten the lifetime of the tube. The circuit I ever
found in a handheld 8W TL lamp did work but gave a flickering light.

I also use a magnifier lamp but a bigger one containing a 22W circline. It
came with an old-fashioned iron ballast and no starter. I had to start it
by hand using the special switch. That is I had to push the button and keep
it pushed for a 6s. During this time the heaters were on. Relieving the
button ignited the lamp... Most of the times. But over time igniting failed
more and more and the circlines seemed to worn out faster and faster.
Investigating revealed the special switch to be worn out beyond repair. So I
got a 20W CFL, got out the electronics, put them in a box and connected it
to the circline. Works fine for several years now already.

petrus bitbyter

"petrus bitbyter" wrote in message
.nl...

"P E Schoen" schreef in bericht
...
I have a desk lamp, with a magnifier and a 12W T4 circline fluorescent
bulb,
that I use constantly for working on PCBs and electronics projects in
general. I bought it several years ago and recently it started flickering
and then died. I replaced the bulb, but still no joy, and after replacing
the blown fuse and two damaged transistors, I found that the little
transformer had an open winding.

So, I thought, a 60W equivalent CFL is actually about 11-13 watts, and the
little circuit in them should work. I had a couple of broken or dead bulbs
ready for recycling, so I opened the bases, cut the leads, and extracted
the
PCBs. After a few unsuccessful tries, I was able to get it to work and now
my lamp is once again operational.

I found some schematics of the CFL driver boards he
http://www.pavouk.org/hw/lamp/en_index.html

Some of those circuits matched what I had almost exactly. It was a little
difficult to follow the explanation of how they operate, but what was
confusing is the four pins shown on the lamp itself, which is also how the
bulbs are made. I assume they are the heaters that are usually activated
with a starter, but I did not find any continuity on those pins. The desk
lamp only had one wire to each of two pins on the circline bulb, but in
the
CFLs all four wires were connected to different points on the PCB. It
would
only work when I shorted the connections that would have gone to the
heaters, and it seems to work very well. It starts to light at 50 VAC and
reaches full brightness at 100-120V, at which it draws about 100mA. That's
close enough to 12 watts for me!

Here's a little clip of my repair project:
http://www.youtube.com/watch?v=e7QJQ...ature=youtu.be

This is good to know. Those little circuits in each CFL have a lot of good
components, including a DIAC and high voltage transistors, and it's
probably
possible to use them to drive small fluorescent lamps for DIY projects or
repair. I doubt they could be used for the 40W tubes, but a driver from a
100W CFL should work on a 20W tube such as are in many desk lamps and
small
kitchen fixtures.

Does anyone know if there is any problem with this?

Thanks,

Paul

PS: GO RAVENS!!!!!

The traditional way of igniting TLs is first heating the heaters and then
start it with a relative high voltage puls. But heating first is not
necessary. The lamp will ignite if only the voltage of the ignition pulse
is high enough. Nevertheless, the heaters cannot be omitted as they
provide the electrons required for the current through the tube.
Especially low power TLs are sometimes ignited this way. When used with
low frequencies i.e. 50Hz or 60Hz, it is said to shorten the lifetime of
the tube. The circuit I ever found in a handheld 8W TL lamp did work but
gave a flickering light.

I also use a magnifier lamp but a bigger one containing a 22W circline. It
came with an old-fashioned iron ballast and no starter. I had to start it
by hand using the special switch. That is I had to push the button and
keep it pushed for a 6s. During this time the heaters were on. Relieving
the button ignited the lamp... Most of the times. But over time igniting
failed more and more and the circlines seemed to worn out faster and
faster. Investigating revealed the special switch to be worn out beyond
repair. So I got a 20W CFL, got out the electronics, put them in a box and
connected it to the circline. Works fine for several years now already.

Don't forget the significant increase of efficiency running the tube at
around 20kHz.

Frequency may also contribute to easier starting, although most CFLs seem to
have some sort of setup to run power into the heaters.

More often than not its a capacitor to bleed some of the AC current via the
heaters, some Ikea branded CFLs I got from a car boot sale long ago had
resin dipped double pellet thermistors bridging the heaters across the tube.

In article , petrus
bitbyter writes

Nevertheless, the heaters cannot be omitted as they provide the
electrons required for the current through the tube.

In other words, used like this, they are not heaters but cathodes.
Presumably this is what a 'cold cathode' tube is.

--
(\_/)
(='.'=)
(")_(")

"Mike Tomlinson" schreef in bericht
...
In article , petrus
bitbyter writes

Nevertheless, the heaters cannot be omitted as they provide the
electrons required for the current through the tube.

In other words, used like this, they are not heaters but cathodes.
Presumably this is what a 'cold cathode' tube is.

--
(\_/)
(='.'=)
(")_(")


Sure. During the classic startup you can consider the heaters to be direct
heated cathodes. Once the light is on they are pretty hot cold cathodes

petrus bitbyter

"Mike Tomlinson" wrote in message
...
In article , petrus
bitbyter writes

Nevertheless, the heaters cannot be omitted as they provide the
electrons required for the current through the tube.

In other words, used like this, they are not heaters but cathodes.
Presumably this is what a 'cold cathode' tube is.

On AC; each end alternates between anode & cathode - the electrode is heated
during the periods when its an anode.

Tubes for iron ballasts often have a "cathode" cylinder enclosing the
heater.

"P E Schoen"

It starts to light at 50 VAC and
reaches full brightness at 100-120V, at which it draws about 100mA. That's
close enough to 12 watts for me!


** You are mixing up "watts" and "VA".

CFL inverters, like most simple SMPS, have a PF of about 0.6 due to the
peaky current wave shape drawn from the AC supply - so VA and watts
numbers differ by about a 2:1 ratio.

You did use a wide band "true rms " meter to measure the AC current -
didn't you ?



.... Phil

On Mon, 21 Jan 2013 04:04:24 -0500, "P E Schoen"
wrote:

I have a desk lamp, with a magnifier and a 12W T4 circline fluorescent bulb,
that I use constantly for working on PCBs and electronics projects in
general. I bought it several years ago and recently it started flickering
and then died. I replaced the bulb, but still no joy, and after replacing
the blown fuse and two damaged transistors, I found that the little
transformer had an open winding.

So, I thought, a 60W equivalent CFL is actually about 11-13 watts, and the
little circuit in them should work. I had a couple of broken or dead bulbs
ready for recycling, so I opened the bases, cut the leads, and extracted the
PCBs. After a few unsuccessful tries, I was able to get it to work and now
my lamp is once again operational.

I found some schematics of the CFL driver boards he
http://www.pavouk.org/hw/lamp/en_index.html

Some of those circuits matched what I had almost exactly. It was a little
difficult to follow the explanation of how they operate, but what was
confusing is the four pins shown on the lamp itself, which is also how the
bulbs are made. I assume they are the heaters that are usually activated
with a starter, but I did not find any continuity on those pins. The desk
lamp only had one wire to each of two pins on the circline bulb, but in the
CFLs all four wires were connected to different points on the PCB. It would
only work when I shorted the connections that would have gone to the
heaters, and it seems to work very well. It starts to light at 50 VAC and
reaches full brightness at 100-120V, at which it draws about 100mA. That's
close enough to 12 watts for me!

One other thing you can learn from this exercise - low cost part
types.

Typical gapped core sizes commonly used in this application can be
designed in elsewhere for $0.02. Similar price ranges for bobbins,
semiconductors, film caps, fuses and electrolytics.

Lots of other things you can do with this stuff, knowing you won't be
beat on material cost.

RL