AKAI Display Retroillumination problems
Q) What can I do about my faint
Q) What happens if I leave my LCD backlight always on?
Q) Can I change the retroillumination of my LCD only?
Q) What is an LCD?
Q) Where can I buy replacement electro luminescent back plates?
A) The display of most of the new generation instruments are all LCDs which stands for Liquid Crystal Display. Why liquid? Well, "liquid" not because there is some liquid in the display as we can imagine it, but there actually is in the molecular point of view: it "flows" as a liquid but maintains an ordered structure of a crystal. There are three type of liquid crystals; the display's type is the NEMATIC one hence the word Twisted Nematic display (TN / STN).
Brief introduction to LCD concept and
An LCD is made of a piece of polarized glass which has on one surface a sort of "drawing" of the actual display segments (liquid crystal) and tracks where the electrons can move on (like a pcb). These segments can form a complete drawing (like a bell drawing on your watch) or just a small part (segment) of something that is needed to compose a complete number or letter (like the segments in the numbers also of your watch) The liquid crystal segments are stimulated by a low frequency square wave generated by the display controller (a dedicated microchip) which is connected to all of them on the LCD - in the case of our AKAI's display. The correct name for it is a passive LCD MATRIX display because it is formed by a number of rows and columns of square pixels that are each a little liquid crystal instead of bigger and bulkier shapes like normal segments. The reason for this is that with a tight matrix you can create any kind of form you want with a definition that is inversely proportional to the single pixel dimension and directly proportional to the whole display area that means the bigger the display and the smaller the pixels, the better your read them and the easier one can make more defined shapes too - exactly like the resolution of your videocard: the higher the better. The whole basics of the LCD function is in the varying a fundamental property of light (that have also electromagnetic waves). What Light? But aren't LCDs passive and don't create light? Yes, infact they are passive and absolutely do not create light, but light is forced to travel through them - that's what your retro illumination panel is for. When Light travels through a non "excited" liquid crystal zone, pixel or segment, it becomes polarized as if it traveled through a normal polarized glass like through a pair of Polaroid glasses - but if that segment is excited by the display controller, then it's polarizing properties change by exactly 90 degrees. So knowing that a polarized light will travel on one plane, we will have only a "single plane" (polarized) light come out of your LCD segment and the rest of the light will be polarized exactly 90deg (the other plane) respect to the one passing through the excited segment(s). Now the final touch: with our bare eyes we would not see the difference between a light polarized on one plane or the other, because the segment still lets light transpare through without turning "black"; this is achieved though by inserting ANOTHER piece of glass infront of the LCD that is polarized with exactly the same angle (or perpendicular) that the LCD has. So now all the light that travels through the complete set of glasses will still be always polarized on one plane so what? Well if a segment (or more) is excited this will polarize the light on the other plane too (90deg) resulting in nearly a complete "light block" giving us the "dark zone" we expect. Just for fun, if you have a pair of Polaroid glasses , put them in front of your AKAI's display and rotate them in both ways and check out what happens!
Now to the retro illumination part. There are two kinds of retro illumination for LCD screens: one is the so called FT type: a small Fluorescent Tube on one side of the LCD glass, just like a normal neon tube, containing Argon with some isotopes is coated internally with a white phosphorous substance that will convert the UV light created by the Argon excited gas by absorbing energy in one form [electricity] and releasing it in visible cool white light but is not so appropriate, absorbs more and doesn't give the same results. The other is the EL (Electro Luminescence) one which is the alternative and efficient type (more evenly distributed) of illumination that is used in the AKAI's LCD (for small areas): a quite thin rectangular so called "EL plate" with a special phosphorous / electro luminous coating gel on one surface is inserted behind the LCD glass. This coating (equivalent to the white phosphorous substance in the "neon tube") generates light when it is stimulated by a particular electrical generator through special contact zones on the back of the LCD. This generator excites the plate with a high frequency high and voltage pulse - yes high voltage, so don't fiddle with an active display or you could get a small but consistent electrical shock! Infact, you probably will have noticed or better "heard" a slight whistle or interference when you get close to the screen with your ear or with some sensitive audio appliance. The audible "noise" is generated by the little inverter (generator) on the display electronics (exactly the transformer/inductance coupling) and the more disturbing interference by the electromagnetic waves generated by the high voltage transients and transformer. The light created by the plate is transported through the LCD glass in a uniform way creating a nice "completely illuminated" look.
If you keep your display on and never turn it off when you don't use it, the plate's EL substance "dies off" with time (like a normal fluorescent tube) and becomes less and less reactive thus releasing less and less light. When this happens you will have to replace this plate with the same type and model to completely restore your LCD's state - this means that you DON'T have to change the whole LCD display and throw away your money for nothing so bare this in mind. An alternative is placing a normal light bulb on the back of your LCD without the plate, but this doesn't give the same results and isn't a very "clean" and neat job - but in extreme conditions, sometimes one needs temporary and extreme measures!
There are a couple of non AKAI related places where you can find these plates for a good price and hopefully are always available. Here are the 2 places I have picked up from our AKAI list: the first one is Backlights-UK which is rather specialised in "music appliance" specific plates (AKAI, Casio etc). Then there is Midi-Rackete, a German site with also an English description of the replacement process with related images. Here are a couple of *original* AKAI replacement EL plates for these AKAI samplers for reference:
Backlight Part # - EL728382J
- S3200 Backlight Part # - EL733752J
I am told they
both should cost around 40$ (around 40€).
A final warning note: by now you may have understood that it is a not so straight forward task replacing this plate. It requires a good "electronics" hand, some fine tools and patience. It is not difficult, but incorrect handling or dismantling of the LCD group will damage or crack the glass resulting in a much graver failure. If you don't feel confident or have never done something like this before, you better ask for specialized help or bring your AKAI in for servicing.