Tuesday, October 28, 2008

VE170 Monitor Repair with LED's

I have noticed that many people find my blog when looking for monitor repair ideas. So here is another one of my ideas for monitor repair. I have in the past fixed laptops by retrofitting them with LED's. The problem with this monitor is that the power supply for the vacuum tube back lighting dies.

The first step is to totally disassemble the monitor into little pieces, then carefully remove the gold colored trays that hold the vacuum tubes. Then carefully remove the tubes themselves without breaking them, like that can be done.

The LED's are spaced at about 1/2 inches apart by using the edge of a cardboard box as can be seen below. This was the test setup using a 9 volt battery, the LED's are spaced every three holes from each other. The LED's are wired in sets of 3 with a 12 ohm 1 watt resistor in series with all of the sets of three LED's. A 10 ohm to 15 ohm resistor would work just as well.

This is a schematic drawing of how it is all wired up. It shows 24 LED's but actually there needs to be 27 LED's in a 17 inch monitor.

This is what the LED's look like in the tray. They have to be angled at a 45 degree angle towards the back of the screen in order to fit and it is a very tight fit. I tried to use a flat front LED so it could aim directly up at the screen but did not see any increase in brightness.

This is what it looks like with the bottom tray full of LED's. There are a total of 27 LED's in the bottom light tray in this photo. There needs to be about 27 LED's in each of the trays. The dark areas are where the resistors are located. I no longer put any resistors in the tray for that reason.

As you might be able to guess the labor far exceeds the value of the fixed monitor. Also you can see in the photo above that unless you space the LED's so they are almost touching each other then there will be blank spaces between them. The ideal solution would be surface mount LED's on a circuit board to provide continuous lighting.

The picture below shows what it looks like compared to a laptop. As you can see it is not as bright and the picture has a purple color to it. Even thought the color looks white to the eye it is somewhat blue by comparison.

The LED's used were 3mm 16,000 MCD bright white LED's found on EBay. There are brighter LED's available that might work even better. I tried using the flat top LED's and they fit better because they are shorter and light the screen more evenly. Also the resistors can be external, wire all of the LED's up in parallel sets of 3 each, then use a 10 to 20 ohm resistor externally between it and the 12 volt power supply.


Unknown said...

What about using a diffuser material to reduce the banding? Something like opaque plastic would work well to distribute the light. Even a piece of onion or tracing paper would probably work, given the low operating temperature.

I've done similar repairs using white case modding CCFLs. They're not quite as bright as the original hardware, but they do work and can be gotten quite cheaply.

Bob Davis said...

There is a reflective coating on the channel the LED's go into. It provides lots of diffusion, the problem is the resistors create dead zones. Maybe if it was made with the resistors outside of the channel or with smaller resistors?

The CCFL mod kits are way too dim, I tried one of those first.

GregR said...

I think you mean MCD (millicandelas) not Lumens.

A 60 watt incandescent light bulb puts out less than 1000 lumens...

Unknown said...

I've got a dead one sitting on my bench that I've been waiting to tear into. I think I'll try this with red LED's and use the monitor for astronomy. Most LCD's put off too much light anyway with the factory lighting to be used with night vision.

Bob Davis said...

I fixed the error so it says MCD instead of lumens now.

Anonymous said...

Grettings from Mexico

I Made this to one of my monitors 2 years back and today it's still working!! so this kind of hack works great.

I didn't use resistors, I just soldered a lot of ultra-bright white LEDs to 2 wires and powered them with a 5v AC. This monitor is still in my workbench, I use it when I repair computers for my clients :D

Here's my hack with pictures: http://minihosting.info/webs/patulawifi/electronica/lcdleds/index.htm

:) patulawifi.com

Bob Davis said...

I have been doing this for years, this was my best one so far. Yours looks a lot better than mine. I was trying to figure out how to do it without the resistors to get better ligting. From you pictures you eliminated the resistors by doing it in sets of 2 LEDS and you eliminated the jumper wires that way as well. GREAT JOB!

Brett said...

Love it! I've wondered why more manufacturers aren't using LED backlights by default. Glad some are now in the ultra-mobile laptops. Also- LED projectors, cool idea too.