I could make a loose inference, about what Lumens are.

In the later part of my childhood – in the 1970s and 1980s – we had incandescent light-bulbs, and we knew that only a small part of the so-called light they emitted was in the visible part of the spectrum. We often used this light-bulb type, because we had no better alternative. We knew that the visible part of the emitted light might have been 15% or 10% of the consumed energy.

Granted, in Industrial or Commercial Lighting, there existed other types of fixtures, such as mercury-gas-discharge tubes, that excited a phosphor with ultraviolet light, so that the phosphor was made to fluoresce. Or in some cases simply – a gas-discharge tube, with a gas-mixture of a composition unknown to me.

But, when I go to buy light-bulbs today, as an adult, like all the other customers, I see Compact Fluorescent Light-Bulbs, as well as LEDs, the brightness of which is stated in Lumens. What I generally tend to find, is that light-bulbs of the fluorescent family, which are meant to be equivalent to the ~Old, 100W~ incandescents, tend to draw approximately 23W, and are stated on the packaging to produce about 1500 Lumens.

Lightbulbs of the LED family with the same equivalence, are stated to draw about 16W, and to produce about 1500 Lumens. I have actually found LEDs, which are stated to draw about 17W, and to produce 1600 Lumens of visible brightness, but which possess a visibly-larger base, from the other types.

If I could just hazard a guess, I’d say that one way to understand Lumens, is to start with the Watts of light in the visible part of the spectrum, and to multiply those by 100. What this would suggest, is that the most-efficient LEDs waste about 1W as heat, while then fluorescents still tend to waste a bit more energy, such as perhaps 8W – some of that in the form of UV light, making those approximately 65% efficient. But this would also mean, that the efficiency of modern LEDs is hard to improve upon. If the brightest variety only seem to produce 1W of waste heat, out of 16W or 17W consumed, it would make most sense to infer that in that range of efficiencies, the Wattage can be translated into Lumens quite easily. More Watts will simply produce more light, and fewer Watts will produce less light. In percentages, the LEDs would seem to have an efficiency of about 94%.

If we have a new light-bulb type, that draws 4.5W, but that produces visible light amounting to 350 Lumens, it would follow from this thinking, that this type is wasting about 1W / 4.5W. In percentages, this would imply an efficiency of 78%.

I suppose that I can offer a comment on the temperatures which the light-bulb-bases of household LEDs reach…

Continue reading I could make a loose inference, about what Lumens are.

I have just opened up one of my laptops.

One of the laptops I own is dual-boot, and is named ‘Venus’ when running in Linux mode. This is a very old laptop, dating back to the year 2005, an Acer Aspire 5020.

In recent months it has been overheating. I have struggled with this problem for some time. But just last night I decided really to do something about it. I opened it up and cleaned its cooling system with a toothbrush.

This was the first time I ever opened up a laptop. I did it with the help of a suggested video. And I am amazed, that after I put everything together again, it still works! Not only that, but it does not overheat anymore.

(Details : )

Before working on this project, I studied This Video.

In my experience, the job of undoing and then refastening many screws is not that difficult to accomplish. But, there were two points to this procedure which I found to be real obstacles:

  1.  At some point in time, one needs to remove a plastic Bezel in the back of the surface of the tablet, which is seen during normal use.
  2.  After that, and after removing the keyboard (easy), one finds a plastic panel which holds the touch-pad, and which needs to be removed.

What I found difficult in both cases, was the fact that these are thin plastic parts held in place by small molded hooks all around the edges, and with no formal fastening mechanism. One needs to use the elasticity of the plastic, to get these hooks to unhinge one at a time, progressively loosening the part.

It is plainly clear, that ever exerting too much force on either plastic plate, will cause it to break. So in both cases I needed to be very patient, and resolve never to exert force exceeding some threshold, even though each part had not yet started to budge.

One hint with how to make part (1) above slightly easier, is to swivel the display back 180 degrees, because the back bezel is also a unit with shrouds over the display hinges. Thus, the hinge-shrouds need to be able to move straight up, and by exerting gentle upward force on the shroud with one hand, and on some edge of the bezel with the other, it is easier to get it started.

What makes part (2) above harder than it seems in the video, is the fact that the audio jacks at the bottom of the laptop during use, are part of what hold it in place, and also count as hinges, which need to be unhooked in a logical way, before any progress can be made with the touch-pad plate.

Also, when disconnecting the display, it is important to note that it has two connections. One is a multi-pin, small-signal connector, that sends video data to the LCD pixels. The other is a high-voltage, very-low-current cable, which connects to a special component underneath the touch-pad plate, and on the side of the motherboard facing away. The gentleman in the video mistakenly referred to this component as “the WiFi block“, perhaps assuming that this laptop used its display panel as a kind of antenna?

The old LCD displays used an electroluminescent back-panel, that needed to be driven by a voltage near 1-2 kV. Since we have taken the battery and the power cable out, there is no danger of electrocution. But as it goes with high-voltage, low-current supplies, it is crucial not to compromise the very thin insulation on this cable as we go.

And, the two leads of this cable need to be reconnected later, via clasps that can also be a bit tricky to secure first, and then maybe secure slightly more, with needle-nose pliers.


When I reassembled my laptop, I found I had made two major mistakes:

  1. I had forgotten to reconnect the ribbon from the touch-pad to the motherboard.
  2. I had failed to reconnect a small power-lead to the motherboard properly, which led to an error message about the wired Ethernet port not working. I had tried to make a connection, but the connector was crooked, so that no electrical continuity was formed.

And so I needed to do this whole exercise 1 + 1/2 times. Luckily for me, the way the touch-pad ribbon connects to the motherboard is such, that one does not need to take the second plastic plate out, just to complete this connection – at least on my version of the laptop. I only needed to undo and redo the back bezel.

Malfunctions resulting from (1) and (2) above are now resolved.

Also, the way the keyboard ribbon connects to the motherboard is a bit tricky to figure out. The manufacturers made it a bit too short to reinsert into its connector easily. The trick to doing that was, to flip the keyboard over completely, so that its ribbon does a backwards loop. That allows us to hold the connecting ribbon short, and to reinsert it into its connector.

The connector for the keyboard ribbon has a saving grace, in that it has a small plastic part that slides out partway when the ribbon is pulled out. This needs to be pulled out, before the ribbon can be reinserted, with the conductive surfaces facing downward. And then, the plastic part can be pushed all the way back in – when successful – and thus hold the ribbon in place as we carefully reorient the keyboard to normal. And one hopes not to yank this ribbon back out.

When I was done I had broken two of the plastic hinges on the back bezel, but astoundingly, that bezel seems to have adequate stability minus those two tabs.

And, I had failed to reinsert two of the ~20 screws at first.

There are dark screws that come short, medium, and long. It is important to remember where the long ones came from: The topmost two corners of the back. And there are 6 shiny screws I can recall, which are all interchangeable.

One shiny screw and one dark screw of medium length fell out of my grasp, and could not be found quickly. I have found both missing screws by now. But by now, the keyboard is being secured with one shiny screw instead of two. Again, it seems to have adequate stability.

And the missing dark screw is about to get put back into the last screw-hole of the back.

If I was to undertake to install the missing shiny screw as well, I would have to take the back bezel off again, to expose the keyboard. I am not ready to do that, and because the KB is also sandwiched into place, I do not think it absolutely needs both screws to hold it as well.


Also, here is a note on taking out the optical drive: That optical drive has a plastic edge-plate. If one has gotten over-confident with it, one can mistakenly pull the edge-plate off the optical drive, instead of pulling the drive out of the laptop. If that happens, two very small parts come loose, and if we value putting the laptop together again correctly, it is important not to lose those parts. Assuming this accident did happen to us.

One is a small dark plastic, almost rectangular piece, which forms the Eject Button. The other is an even smaller transparent piece, which is the Drive LED window. The mere fact that those two pieces were on the loose, did not mean in my case that anything was permanently damaged. They were fit in place loose during the assembly of the laptop by a machine.

The trick to putting those back, is to insert the transparent part into the dark part, and then to place the dark part back onto the electrical contacts, so that the transparent window is indeed in front of the LED, Before attaching the edge-plate back over both, thus sandwiching them.

The contacts for this switch and its LED are recessed inside the side of the optical drive. It can all be reassembled manually, into exactly the state which the manufacturers left it in.

Luckily, this laptop has an optical drive without a tray that extends. When I push the Eject Button again, after my work, sound comes from the inside, as it would if the drive was to eject a disk by itself. And the LED blinks through my reattached LED Window. And the faceplate stays put as it should.


The two critical components which were overheating before – according to the ‘gkrellm’ Linux widget – are now running 20⁰C cooler than they were before, under heavy use. And everything works.