The only BIAB with the means…

I’ve been wanting to learn music for a while now – I want to be able to create music for other projects (games or animations, things like that) and also I think it’s just a good skill to have, I want music to be part of my household in general. As I’m learning more about music and how to play it, I’m also building a little collection of gear to use in musical projects. My first acquisition along these lines is the Yamaha QY-70 synthesizer. It’s a portable MIDI workstation released back in 1997. I plan to give it a new paint job, but first I wanted to give it a functional upgrade – a backlight for its LCD.

The Korg DS-10 software I got is an emulation of an analog synthesizer – specifically it’s supposed to be similar to Korg’s MS line of analog synths. It’s a fun piece of software and I want to do more with it, but it’s a bit limited in terms of polyphony. Anyway, the people who made DS-10 formed a company called Detune and released another “Korg” product, available only in Japan – Korg M01. M01 is a polyphonic sequencer with a full set of general MIDI instruments based on sounds from the Korg M1. So while DS-10 gives you the ability to experiment with sounds, M01 is better for rich instrumental arrangements and such.

The idea of getting Korg M01 was very appealing to me – but a few things held me back. Since it’s only available in Japan, I’d have to import it, bringing the total cost of the software to the $90-$100 range – high enough to make me think twice before buying it. And since it’s on a game console, it’s a closed platform: data storage is limited, it’s not possible to hook up to a MIDI controller to enter data, and there’s no direct way to back up and restore saved data. Plus the input is limited to the touchscreen (which isn’t multi-touch) and the game controls. From my experience with DS-10 I didn’t feel like that was a great way to work. If I were to go with a software solution, there are iPod Touch apps that cost a lot less and benefit from the multi-touch screen. Or I could get some actual hardware.

And this brings me back to the QY70. Of course I was familiar with it through Freezepop, and since it’s kind of old at this point I figured I could get a pretty good deal on one. It’s bulky, but portable, it has a two-octave keyboard (not a great keyboard, but it gets the job done) – and I felt it could be a good fit for me. As I’m still just learning to play piano I find it’s nice to have an instrument that’s just kicking around to experiment with. So having the QY at hand is great for that kind of random experimentation.

Anyway, on to the backlight modification. Before I started the project, I did a bit of research into the kinds of lighting modifications people had done with the QY. I found this modification, using LEDs to shine light into the LCD glass from the sides. Early on I considered using this method, perhaps with a larger number of LEDs and additional holes cut in the metal frame around the LCD to let the light in – but it seemed to me that this would be too much power for too little yield. I was surprised to learn that people also used modification kits for the old Game Boy Advance on the QY-70. I actually bought and installed one of those kits into my old GBA long ago (it was the Triton Labs Afterburner kit, which had a huge following and may have actually prompted the development of the GBA SP) – these are transparent side-lit light guides that are installed in front of the LCD screen. On the Game Boy Advance, the Afterburner was actually quite effective, though the colors tended to wash out. Assuming one can still obtain these kits, I think the trade-offs are only slightly better than the side-lighting modification: you get better coverage of the screen, but it’s still not consistent coverage – you’ve got hot spots and dark spots – and you have to run two or more LEDs to do it.

Ultimately I decided the best way to go would be to use an electroluminescent backlight. EL lamps aren’t terribly bright, but they give you enough light to see the screen – and the distribution of light is very even across the panel. EL lamps do require an inverter to produce their high-voltage AC, and I was concerned about the possibility that this would result in audible noise, or RF noise picked up by the QY’s audio circuits. Another problem was that I couldn’t find a place to buy an EL inverter that would be small enough to easily fit into the QY70. Also, I had no idea about how to proceed with such a modification. Putting the EL panel behind an LCD is simple enough – but non-backlit LCDs are backed with a foil reflector that won’t let light pass through. Would the LCD still work if the reflector were removed? Did I need to replace it with anything? (Backlit LCDs normally have a semi-transparent reflective layer – but I had no idea where to get one.) Would I still be able to see the LCD with the backlight off? I had no answers to these questions.

Finding the answers turned out to be a problem of coming up with the right search keywords. I knew that someone, somewhere must have done this kind of modification in the past. But probably it’d be some time ago (how many devices these days are manufactured with black-and-white, non-backlit LCDs? How many of those do hobbyists modify for backlights?) – I wasn’t sure the info would still be on the web. Searching for things like “LCD backlight modification” was mostly fruitless, so I tried to think of specific pieces of gear that likely would have had enough technically-minded fans that the info would be out there. My first guess was the HP48 calculator, which was popular with engineers when I was in school. I didn’t find info about backlighting the HP48, but the search did turn up a page about backlighting HP’s old handheld DOS PCs. This page was incredibly enlightening. It detailed the whole process: peeling off the reflective layer, dealing with the glue underneath, and comparison shots showing the slight loss of display contrast when the backlight was off. It also led me to Backlight 4 You, a shop selling backlight conversion kits for various devices, as well as an EL inverter board that was both small, and promised low amounts of noise when in operation. So I ordered an inverter board and an EL panel and planned out the modification.

Initial Exploration

Prior to making any changes I wanted to open up the machine and look around. It’s often a good idea, when hacking on a piece of gear, to take photos along the way. If I screw up along the way somewhere, I can refer back to the photos to see how it’s supposed to look. Plus it makes for a good comparison, before and after. I don’t have a second QY so at the moment this is the only comparison I can provide between the unmodified machine and the QY after the backlight mod.

Reading the Keypad

It’s not enough to just install a backlight, you need a way to turn it on and off. At least, I think so. I could have added a switch, but it seemed to me that it’d be better to use the keypad to turn it on and off. This meant I needed to add a microcontroller to the QY, which could monitor the keypad matrix as the QY scans it, so it can pick out the bits of information it wants. I considered a few different ways of triggering the backlight – holding down this key, or chording these two keys, etc. – ultimately I settled on Shift-F3. Shift-F1, Shift-F2, and Shift-F4 are all used by the QY to perform different tasks, but Shift-F3 is unused and the machine apparently ignores that particular key combination – so it was perfect for my needs. It took me a while to get the keypad monitoring code to work, however – I seriously underestimated how fast the keypad scan is done. I thought each row would be scanned for a millisecond or two, actually it’s more like a few microseconds. I needed to optimize my code for speed. The first version (which didn’t work) was an interrupt-driven program that put the microcontroller to sleep while waiting for pin states to change – that was slow enough that, when I got it “working”, it only worked about half the time. So I ditched the sleep code and the interrupt system and built a tight loop, first monitoring the keypad row containing the SHIFT key, and then the one for the F3 key. That version worked beautifully.

Installing the EL Inverter

With the keypad issue resolved, it was time to deal with the EL panel itself – get the panel and driver situated in their new home, wire them up, etc. After a little while I found it convenient to remove the LCD from its module to get it out of the way (among other things I was afraid a stray blob of solder would land on the panel, and melt a hole in the front polarizer or something…) – when everything was wired up, I booted up the QY to see if I could turn on the backlight using Shift-F3.

Preparing the LCD

At this point, just about everything was done except preparing the LCD itself. This part is where it gets scary. This is the “point of no return” (well, almost…) – at this point I couldn’t accomplish anything more until I removed the reflective layer from the back of the LCD – and once removed, it probably wouldn’t be possible to replace it. Removing the reflective layer was a bit scary, because physical stress on the LCD panel caused the display to go all wonky for a while. I figured it’d probably straighten itself out, but I wasn’t 100% sure of this. I felt there was at least some possibility at this point that I’d just killed my poor QY’s LCD.
Once the reflective layer was off, there was a bit of a fiasco… See, from what I’ve read online, in projects like this, usually you need to do something about the adhesive that’s left behind after you remove the reflective layer. Some adhesives you can scrub off with alcohol, others you can’t really. It seemed like mine was probably the latter – which I’d learned are best handled by sticking a clear layer down onto the adhesive (so it doesn’t adhere to your backlight and give you irregular spots) – I’d gotten just such a clear layer as a bonus from, but I decided to see if I could just take the adhesive off with alcohol. This wasn’t a great decision, frankly it made a slight mess of my LCD’s surface. And then I ruined the clear sheet I’d gotten from backlight4you while trying to clean off fingerprints I’d carelessly deposited… Whoops… So I stuck some frisket film on the back instead.
For anyone attempting this modification: Since I did this I have learned that conventional wisdom when removing films from LCD displays is to pull them off in a direction parallel to the surface of the LCD, as this minimizes the physical stress on the LCD glass. I didn’t do this. I don’t know if pulling parallel to the surface of the display would have prevented the display from having all those weird artifacts during the process, or to what extent I really was in danger of destroying the display – but it seems to me that it’s good advice. Next time I’ll do it that way.

Rebuilding the QY

Finally, it seemed everything was in order, and it was time to reassemble the QY. The main challenge that remained was putting the LCD back on its module. This is a bit tough because the LCD has to make contact with a bunch of pads on the PCB – but it’s not easy to see where precisely the LCD has to go relative to those pads. If you look at the rubber bits that connect the LCD to the PCB, you can see the impressions of where those pads made contact… Instructions online suggested marking the LCD before removing it from the module so you have a reference for how to re-align it again. I didn’t do that… Probably should have. But this was probably the third or fourth time I’d disassembled the QY’s LCD, and each time I got it back together with a little careful alignment and a little trial and error. It took me a few tries this time around, fortunately this time I took some photos to share, to show what goes wrong if you don’t get the LCD reseated properly… And how the LCD can still be OK in the end after all this scary stuff. :)


In the end, I think it turned out pretty good. Without another QY to compare it to I couldn’t tell you to what extent the removal of the reflective layer has hurt screen visibility. Not much, I’d say. It may even be better with the yellow behind it… But it’s hard to say for sure without a direct side-by-side comparison. With the yellow EL (off) behind it, the screen takes on kind of a pea-green look, like the original Game Boy. The EL inverter does produce some audible noise, but as far as I can tell it’s not affecting the QY’s audio output at all. I hooked it up to my speakers and turned the volume up, and turned the backlight on, and didn’t hear any hum from the speakers… Though I’m no audiophile. And the backlight lights up. Great! Except about five minutes after I took the last of the photos, it started going flaky and then stopped working. :) I think it may be a bad connection on the EL inverter board: I had to rearrange all the connections on the board to optimize for the available space, and one of the solder pads lifted off because I was careless when removing the inductor… I patched it up, of course, but it could be that a reliability issue with that fix is causing the failure. Or it could just be that the wires to the EL panel have broken at one of the solder joints, or that the EL driver is shorting itself out against the RF shield. I’ll know soon enough…
(It turns out the backlight was failing because of a connection problem between the EL panel and one of its metal leads. I had to arrange to put a little pressure on it, to keep the lead in contact properly. I’m not sure why it wound up having that problem… It could be physical stress that was placed on the panel at various times, or it could be that the heat of soldering the wires on damaged the connection. At any rate, hopefully it stays fixed…)

(Bonus Material)
In case anyone is interested, here is the PIC assembly source code for the keypad scanner as well as the layout of the QY70 keypad matrix. The assembly was written to work on a PIC16F688, though it should work on most PIC16F series with minimal alteration. (The keypad scanning code doesn’t use pin change interrupts or anything like that – it just busy-cycles trying to read one of the two pins, and then (upon success) the other. This was necessary in order to get it working reliably.)

22 Comment(s)

  1. How’d you even find one of these? I want one, but even the almighty Google Shopping search proves fruitless.

    Skinr | 2012-03-19 | Reply

  2. The QY-70, you mean? There’s a ton of ’em up on ebay. Most of them right now seem to be price-fixed in the $130-$180 range, but from time to time they do turn up at more reasonable prices or as a normal auction.

    tetsujin | 2012-03-30 | Reply

  3. Hello,
    Where did you get the EL-Panel?
    In backlight4you not have adequate size for the QY70-QY100 (6x9cm)

    Albert | 2012-10-01 | Reply

  4. I don’t remember where I bought the panel. I think I got it on ebay. It was a relatively large sheet which I cut to size. Ebay can be a good place to buy certain kinds of components – though now and again someone will sell you something faulty… I wanted to save some money on the panel but still get a color that would be both fun and practical. backlight4you was a great resource for this project, but for roughly what it would have cost to get a cut-to-size panel from them, I bought an oversize panel on ebay and cut it down. I honestly don’t have enough experience with EL panels in general to rate the quality of the panel I bought – but I’ve been generally happy with it. I do wish the lit color were more yellowish, but I don’t know if that’s something EL panels can really do.
    Incidentally, you mentioned a panel size of 6x9cm – this is not correct, at least not for the QY70. (I think the screen size of the QY100 is the same, but I don’t own one…) The display in the QY70 is an Optrex 50202N – the whole module is 95mm x 58mm, while the viewable area is only 62mm x 44mm. Looking at my notes, I apparently cut my EL panel down to 75mm x 50mm – which was the largest panel size I could fit in the LCD module, and actually a bit larger than is really necessary, I think. So if you want to get a panel from backlight4you, there are some that are close enough in one direction, and can be cut down in the other direction. The 157mm x 47mm panel, cut down to 75mm x 47mm, would be more than enough to light up the viewable area of the screen.
    If you plan to do this mod yourself, please do me a favor and let me know how it turns out. I had a lot of fun with this project. It was a bit scary in places but it turned out great and I’m proud of the work I did with it. I owe much of my success to the instructions I found on the HP palmtop backlighting page and backlights4you… But if my work on this project has helped other people to light their QY’s, that’s really cool!

    tetsujin | 2012-10-01 | Reply

  5. Wow, you really did a great job on this description of your process! Your work on this is an inspiration to me. Thanks for all the effort you put into sharing this with the world. Bigtime kudos!


    Peter Paulson | 2014-06-12 | Reply

  6. Thanks! I can’t help but feel that I learned (and passed on) this information at least 10 years too late, though. I just imagine what I could have done with my old Game Boy back in the ’90s, if I’d known this stuff back then.

    tetsujin | 2014-06-17 | Reply

  7. which button is F3, where can I get the microcontroller and how do I program it?

    Michael | 2015-12-09 | Reply

  8. The four gray keys immediately to the right of the screen are the function keys. F3 is the third from the top.
    As for the microcontroller, there are a few ways you could do it.
    The micro I used is a PIC16F688. You can get it at parts suppliers like Mouser or Digi-Key. I used the surface-mount version with a custom PCB, but there’s probably enough free space inside the QY-70 to use the larger through-hole PDIP type on a generic off-the-rack PCB instead. (It’s much easier to solder, just takes more space…)
    Unfortunately, programming the chip is where things get a bit dicey, as you need an extra bit of hardware (a “PIC programmer”) to write the code onto the chip from your PC. Hobbyist versions can be had for $30 or so, but I wouldn’t recommend it unless you’re planning to continue doing PIC dev. Personally I’ve been gradually moving away from PIC toward the AVR microcontrollers used in Arduino.
    A better option (if you’re not particularly circuit-inclined) would be to get an Arduino-like board, something small like the Arduino Pro Micro, Teensy v2.0, or Trinket; something you can connect to the PC directly via USB so you don’t need to buy extra stuff. These boards aren’t as small as the PCB I used but they may be small enough. But the difficulty there is that somebody would need to rewrite the firmware to work on the Arduino (since it was written for the PIC). It’s not that complicated, just a tight loop that continually monitors the keyboard lines and toggles the state of the backlight when the right keypress is detected. I wouldn’t mind getting you started, translating the firmware to C for Arduino (or whatever) and things like that – but if it doesn’t work right away I won’t commit to debugging it for you, at least not for free. :)

    tetsujin | 2015-12-09 | Reply

  9. Very cool page.

    A few questions:
    1) I was wondering what the impact on battery life is with thebacklight panel on constantly?

    2) Also, would this panel be a viable candidate:
    (It seem to be the right size after trimming)

    3) Lastly, where could a get a 12 volt connection of the pcb when running on 1.2v rehargables? Is there somewhere on the PCB that I can tap into after it is stepped up to 12v or would I need a transformer?

    4) if you had the choice, would you have used the same color? If not, which color would you pick now?

    5) is there anyway to dim EL panels via a potentiometer?


    Tray | 2015-12-13 | Reply

  10. 1: I don’t know how much impact the EL panel has on battery life. I never metered it (and at the moment I’m not even sure where my QY70 is…) But based on specs I found online for the QY-70’s battery life, and the power draw of a typical EL panel, I’d guess it cuts battery life by around 25-30%. I’ll meter it sometime and get you a better answer.

    2: Regarding the choice of panel, you can use almost any panel. As long as it’s big enough, you can cut it down to the size you need, seal up the edges, and use it. Though you do have to consider how the choice of panel affects ambient visibility (see answer 4)

    3: I don’t know if there is a 12V connection in the QY-70. I think my inverter’s running on 5V, as are most of the QY70’s internals. (I think I took the 5V for both the inverter and the microcontroller from the LCD itself.) So you would want to find an EL inverter board that can run on 5V. Generally speaking the choice of inverter may require some care; Some inverters are designed for greater loads (like long lengths of EL wire, etc.) and may not be power-efficient (or even stable) when driving a relatively small EL panel.

    4: I think the color I used worked out just fine. Really, I think any color would probably be fine when viewing the backlit screen in the dark. When choosing the panel I was more concerned about how the screen would look under conditions of moderate-to-bright ambient light.
    When there’s a lot of ambient light, the EL isn’t bright enough to make much difference (really, under bright lights you’d hardly even know the EL was on at all), and so the performance of the screen depends critically on how well the screen’s backing reflects that ambient light.
    Originally the LCD had a reflective backing, but it’s opaque, so I had to remove it to allow the EL light to pass through the screen. (Normally an EL-backlit LCD would have a translucent reflective backing, so it can reflect ambient light but also allow a backlight to work… But I had no idea where to buy that material – not a big market for people tearing apart 20 year old LCD panels to backlight them – so I did without it.)
    Therefore, it was critical that the EL panel I chose reflect a decent amount of light, because it was taking the place of the reflective backing. I chose yellow because it seemed like it’d contrast well with the slightly purplish hue of the LCD. I haven’t had the chance to directly compare my modified unit to an unmodified one to see how it’s affected the LCD visibility in bright conditions, but I think it’s almost as good as it was before. In dark conditions, of course, the backlit LCD wins hands down. :)

    5: I don’t know too much about dimming EL panels, but from a cursory web search it seems like it’s complicated. An EL panel is more like a capacitive load than a resistive one, so it’s not as simple as attaching a potentiometer. You could use a method like PWM, but that, I guess, can endanger cheap inverter circuits if the rapid on/off switching isn’t timed favorably. Honestly I don’t know. Personally I don’t think there’s much point anyway. EL panels aren’t super-bright to begin with. Apart from maybe saving some power in really dark environments I don’t think there’s much to justify opening that can of worms.

    tetsujin | 2015-12-13 | Reply

  11. To go back to the question of how much power the backlight draws, I found my QY-70 and did a few tests:

    I tried metering the current draw from the AA’s but unfortunately even with the backlight off the QY70’s power drain is beyond the range of my meter. (I need a better meter!)

    In order to meter the current usage I had to use a 12V supply. (Internally the QY-70 regulates this down to the 5V it needs for most of the unit. As the supply voltage increases, the unit draws less current, so using a higher voltage allowed me to measure the current with my crappy meter.)

    With the backlight off, the machine drew about 230mA at 12V.
    With the backlight on, it drew about 250mA at 12V.

    Those numbers for the current draw will be higher when run from the 7.5V-9V of the AA batteries but the proportion should be roughly the same. The take-away here is that the backlight uses about 10% as much power as the rest of the machine. So battery life with the backlight on should be about 90% of what it’d be with the backlight off.

    Based on these figures, the power consumption of the EL backlight (approx. 240mW) is roughly equivalent to four LEDs. Not super-low-power, but compared to the rest of the machine (appox. 2.75W) it’s not too bad.

    Also, going back to that 12V question: there is some kind of higher-voltage supply in the QY-70. I don’t know the details (particularly, how much current it can provide) but it’s there: the LCD’s contrast knob is connected to it, the voltage is used to provide the “LCD drive voltage”, and it’s probably also used for the “To Host” port. It’s negative voltage (-10V, I guess?) so you could get 15V by connecting to +5V and -10V. You could tap it at the contrast knob (just pick one of the pins whose voltage doesn’t change as you turn the knob) – but like I said, I don’t know how much current you can pull from it.

    tetsujin | 2015-12-15 | Reply

  12. Thank you for your response! I’m considering doing an EL wire wrapped around the edge of the LCD screen (for fear of ruining it by peeling the backing). The microcontroller may well be biting off more than I can chew, so a discreet button may be my best option, though altering the case may deplete resale value. Thanks again! You are DA MAN!

    Michael | 2015-12-15 | Reply

  13. The microcontroller does complicate this project quite a bit, unfortunately. Another option would be to simply leave the backlight on full-time. This does decrease the battery life, of course, by about 10% if my measurements are right… Or, as you say, you could install a switch somewhere.
    One option for installing a switch might be to remove the “Host select” switch, and mount a new switch for the backlight in that hole. You’d lose the ability to connect to a PC via RS-232 or to a mid-’90s Mac via ADB… Personally I think that’s no great loss. (Nobody has a serial port any more, and the QY-70 host software expects to talk to a MIDI device anyway… So at this point it’s easier to just get a USB-MIDI adaptor and connect it via the regular MIDI ports. Another mod I had planned was to create a custom USB adaptor I could install inside the unit and replace the HOST port altogether… Haven’t got around to that one yet.)
    But for what it’s worth, unless your QY is in really great condition I wouldn’t worry about resale value. I think it’s better to do what makes the machine useful for your own needs. It’s an old piece of gear at this point…
    As for side-lighting the screen with EL wire, I think it wouldn’t be bright enough. When side-lighting the screen, the light will be most intense right next to the light source, and significantly dimmer in the middle of the screen. EL isn’t super-bright to begin with: the whole benefit to EL is that it puts out a uniform glow over a larger area, but that doesn’t help you if you’re side-lighting. Side-lighting can work, but you need a brighter light source. A number of mods have been done side-lighting with LEDs: I think backlighting is a much better option but the LED projects are relatively simple and they do get the job done.
    The goal when lighting the screen is for white pixels to reflect a large amount of that light, and black pixels to reflect much less. But when the light is coming at the screen sideways, as with a front-light or side-light, some of it will just go straight out the screen to your eyes, making that black level brighter and effectively cutting the contrast of the screen. Back-lighting doesn’t have that problem because all the light has to pass through the LCD for the viewer to see it. It’s a more complicated modification but the results are better, too.

    tetsujin | 2015-12-17 | Reply

  14. Thanks for the info.

    I ordered a Panel with a 5v inverter, so I will be able to give this a try in a few weeks.

    I was reading the precautions about not coiling the wire from the inverter… Should I add some insulation around that wire prevented it from interfering with the other circuits on the QY? I was thinking of perhaps putting it through some sort of rigid plastic tube (or heat shrink) to prevent any voltage jumps to other circuits… Do you think it’s necessary?

    Tray | 2015-12-18 | Reply

  15. When I started my project I was very concerned about interference from the inverter: not so much the possibility of the AC lines making electrical contact with something (simple insulation takes care of that) but the electromagnetic interference. I was worried I’d hear the inverter’s oscillation in the QY’s audio output. Solving that, if it had been an issue, would probably have required adding metal shielding between the inverter and other parts of the machine. Fortunately that appears to have not been a problem.
    Also in my install, the inverter board is directly attached to the LCD, so the path for the AC is very short. I used some bits of electrical tape to keep it from making contact with anything else but that was about it.

    tetsujin | 2015-12-18 | Reply

  16. OK well I finally got my screen and inverter and I just want to ask some final questions before I give this a shot:

    1) The inverter that came with my screen is quite large… there is no way it will fit inside a QY70, but it does fit in the QY100. However, it will be literally sitting on top of the SmartMedia card reader. Since I have no other magnetic field meter, I used a compass and I could discern no magnetic field but I am a still a bit concerned about messing up the card reader… Should I be worried, or is the compass test a good enough indicator of no serious magnetic field?

    2) How did you manage to locate such a small inverter? Almost every one I have see seems to be about the same size as the one I have. Just curious if you had to order that special? If so, do you recall the part info? (I would like to do this on my QY70 as well, assuming I am successful with this QY100).

    3) I saw that you mentioned previously the idea of replacing the PC/midi switch with another switch to control the backlight and I was wondering if the switch that is already there could be used to power the backlight? I had read that one of the pins in that miniDin connector was 5 volts but you’re article mentions -10 volts, so I am a bit confused. Not sure if the pin is always 5 volts or if the switch toggles it. I know that you got your power from the LCD, but those pins seem a bit too close for my limited soldering skills, so just thinking that perhaps the midi switch might work… I guess I will know more once I start, but just thought I would see if you have any input.

    3) I practiced removing a reflective layer off a broken HP100 screen and it went well (since it was broken, kinda hard to say if I stressed the screen too much, but I did make sure to pull parallel). Anyway, I was wondering if you needed to use a razor blade on the QY screen or if you were able to peel by hand. I would prefer to peel by hand, but my concern is that in trying to avoid a blade, I might be putting too much stress on the screen. Anyway you mentioned scratches on your LCD, so I thought perhaps you used a blade on it.

    4) When you said previously that simple insulation was enough protection from the inverter wire, did you mean the insulation already on the wire (or additional insulation)? I just want to double check because my wire from the inverter to the EL panel is going to pretty long and is probably going to be lying on top of alot of components… I could make a very circuitous route, but not sure if a really long wire is a worse idea that simply going over the board in a direct shot.

    5) What do you recommend for sealing the edges of the cut EL panel? I had read something about varnish somewhere, but wasn’t sure if that was the best route (and not sure exactly what type of varnish to use… All I have is wood varnish). I though perhaps lining the edge with packing tape, but either way I am concerned that whatever I use will appear on the edges of LCD screen (and is packing tape even a good idea?)

    Anyway, Thanks so much for all the help and previous info. I am getting close to that “point of no return” so I am probably just being a bit over cautious… But I figure it is better to get the answers beforehand than being stuck halfway through!

    Tray | 2016-01-03 | Reply

  17. Hello again,

    I actually gave this a shot already so I figured out most of the above questions (or at least they are kind of moot now).

    Due to required placement of the large inverter, I opted to splice into the LCD wires rather than have a really long run for the 5v cable, and that worked well.

    Made the same mistake with the LCD glue (tried to remove it)… Got it all off, but really was not worth all the effort.

    Skipped the switch for now and just made it so the backlight is always on…May find a very small switch and add it in later.

    The only real (fairly minor) issue is the sound from the inverter is a bit louder than I’d like. There is no detectable interference or audio artificats in the outputed audio from the device (which is awesome), just the actual sound of the inverter itself is a bit louder than I’d like.

    How loud is the micro inverter you are using? Does it produce a noticable hum when the QY is in use? I was also curious if you made the inverter based on the one over at

    Anyway, if you have any suggestions for quieting the inverter, I would be very interested. I did a bit of research about ground loop issues, but not sure if that applies here.

    In any case, I still really like the backlight and I can definately live with the inverter hum, but I would like to reduce it if at all possible.

    Tray | 2016-01-07 | Reply

  18. Update/Correction: Turns out that I am getting interference on the audio out. I didn’t notice on the cheap headphones I was testing with previously, but as soon as I plugged it in to a powered speaker I could hear the interference clearly.

    I think the interference may be coming from the fact that I had the EL power wire take a really long route to the inverter. It literally goes half way around the circumference of the case (mainly because there is only a gap at the bottom to feed thru on the QY100. I am thinking that perhaps a shielded wire would help, but then I doubt that would help with the overall hum of the inverter (since it made that hum even before I installed it).

    Tray | 2016-01-07 | Reply

  19. Hi, sorry I missed your comments when you posted ’em. I would have liked to offer a more timely response, especially as you were entering the critical stage of your mod. I’m pleased to hear that somebody else has taken a crack at this, and especially glad to hear that your mod turned out well. (I’d love to see it!) To answer your various questions…

    • The inverter I got was this one (or a similar one?) from Backlight 4 you. Going into the project I was concerned about EMI and audible noise from the inverter, but Backlight 4 you says their inverter is very low-noise and low-EMI. (A lot of the inverters out there are made for larger panels or for EL-wire, so they need to be able to provide more power than what we need for this application.) The board itself is audible when it’s operating (I can hear the backlight by putting the QY up to my ear when it’s on) but as far as I can tell it produces no hum in the QY’s audio output. (I’ve tested with headphones as well as amplified speakers.) Audible noise from the inverter is to some extent unavoidable as far as I know, so the only thing to do if you want to eliminate it would be to install soundproofing around the inverter. Humming in the QY’s audio output would be the result of electromagnetic interference: best way to avoid that is to move the inverter and wires farther away from the audio circuitry, or install electromagnetic shielding.
    • There are various voltage sources in the QY-70. Honestly I don’t know what they all are, or where. In my mod I just use the +5V that is the main supply for the machine’s logic. There is another, higher voltage supply that is used as part of the contrast wheel for the LCD, and because the host port speaks RS-232 (among other things) it probably has a 12V supply as well. But I don’t know how much current these sources can provide. More exploration would need to be done to determine if these sources could be suitable for running a 12V inverter or LED backlight.
    • Good thinking, getting a trash LCD to practice with. Though, as you say, it’s hard to tell how it turned out if you can’t test the LCD when you’re done. As for the razor blade, I probably used a blade to lift a corner of the reflective layer, but once I had something to work with I just peeled it off. I’m not sure of the exact nature of the minor cosmetic damage I inflicted on my LCD. It could be a smudge of leftover adhesive or something from when I removed the reflective layer, or perhaps I damaged one of the polarizing filters while handling the display. But it’s very minor, it’s mostly just visible when the screen is off.
    • When I said simple insulation was adequate for the wires coming off the AC, I was referring mainly to insulating the surroundings from the electrical current from the inverter. But electromagnetic interference is another matter. Shielded wire (with the shield attached to the unit’s ground-plane) may help if the inverter is producing audible hum in your unit’s audio out. In my install I was able to put the inverter right next to the LCD, so the connecting wires are very short. Longer wires could act as an antenna, but shielding should help to counteract that. Another thing that may help (not sure how much, though) is twisting the two wires together. They carry opposing current (or, rather, the same current in different directions) so keeping them closely coupled minimizes their electromagnetic output. But shielding is still a good idea. Getting a different inverter might be an even better idea, though: if you can reduce the EMI and audible noise right at the source, that’s better than attacking the problem with sound buffers and EMI shielding.
    • In my mod I used cellophane tape to seal the edges of the panel. That’s probably not a great choice, honestly. It gets brittle as it ages. Electrical tape might be more durable, but of course it’s opaque… Backlight4you recommends a “varnish” but I don’t know the details. I’m afraid I don’t have a good answer to this one.
    • Based on my tests of the QY-70’s power consumption, it’s probably not too important to include an “off” switch for the backlight. The QY-70 itself seems to use enough power that the drain of the backlight is pretty minor by comparison. I expect the QY-100 is similarly power-hungry (though I haven’t tested one to find out) so if you don’t get around to installing a switch it probably won’t be a big deal.

    Anyway, I’m glad to hear that it’s turned out well. The EMI issue with the audio output is an issue for sure, though… I don’t know which inverter you’re using but it may be worth trying out the backlight4you one. I’ve been very happy with its performance, it may be the simplest way to resolve the noise problem.

    tetsujin | 2016-01-13 | Reply

  20. Thanks for the info, no big deal about the late reply, I was probably just being a little over cautious anyway… On the positive side, it kind of prompted me to just take the plunge and move forward! :-)

    I was able to get rid of the hum in the audio output (as well as reduce the overall hum of the install) by shortening the route of the AC wire from the inverter to the EL panel. Whats really odd is that the EL panel is now the part that is humming the most, the inverter is nearly silent (or too quiet in comparison the the panel fir me to even hear it).

    I was able to also reduce the hum be inserting a series of 2×8 ohm resistors between the inverter and the ground (it was all I had handy). It causes the EL panel to dim a bit, but on the plus side the hum gets quiter (or at least lower in freq). I just ordered a 100 ohm trimming pot to fine tune the resistance/brightness/hum ratio. Not sure if this is going to shorten the panel/inverter life, but I wouldn’t think so (since I am under-powering an inverter that is capable of powering a much larger panel…I mean the inverter is probably overpowered for this tiny panel to begin with… Though I am not sure if that argument supports the logic of under powering it. :-) )

    BTW, I just figured I’d try the resistors after I found this article when looking for hum reduction ideas: (under section “Is it really that simple”).

    I also changed from grounding the inverter at pin 7 on the LCD wire to simply grounding it to the chasis (my reasoning was that pin 7 is a digital ground, so I though it might not be the best choice for grounding the EL panel…which I would imagine is an analog circuit (please correct me if I am wrong). Also, I realized that when I saw your ground wire going to Pin 7 (in the pics in the article above), it might have actually been the ground for your PIC controller and not the EL panel as I had orginally assumed (it took me a second look to notice only one wire is connected to Pin 7 in your pic, not 2 wires as I has first thought)

    I did check out the electronic inverters from backlight4U, but they were setup for 3v so I was unsure if I would be able to use it with my 5v panel. Did you buy your inverter pre-built from them or did you buy the board/kit and make a 5v version?

    As for shielding, I tried twisting the AC wires last night but it had no impact on the external hum, but again, the audio out is already clean based on the other tweaks I tried, so it might have gelped if I still had a really long AC line. I don’t have any shielding or shielded wire, but I plan to order some and give those ideas a try. Any idea what guage wire I would use to replace the AC wire with a shielded twisted pair on the AC line?

    BTW, I also thought about adding an inducer (or possibly a capacitor) but I have no idea what size to use or where/how those would get wired into the circuit (or if they would help at all).

    I should mention also that I did find out that varnishing the edges of the EL panel actually refers to nail varnish (meaning nail polish I would imagine). Alternatively, super glue can be used as well (and I would recommend it over nail polish since nail polish is really thick and clumpy). I used both (overkill, I know) and found that the easiest way to apply the super glue is to douse a Q-Tip and run it along the edge (several coats with drying in between)… It greatly reduces the chances of getting glue droplets on the edge of the panel. I have been wondering though if the reason my panel is now humming (and not my inverter) is due to a bad seal on the EL panel edge? I really sealed it well abd I would think a bad seal would have a much more obvious side effects (considering the metal frame and all), but it does make me wonder… I also wiukd rather not open the LCD again since the clips gave a limited number of bends theywill withstand. Any thoughts?

    Lastly, I videod the whole process as I went along, but today my Macbook totally died (the infamous video card failure that Apple has finally aquiesed to covering (News article: )
    I have not made appt yet with apple, but hopefully it gets covered (thank goodness it happened now as the repair window closes in about a month! I was so bummed when it died until I ran accross that news story!)

    Anyway, as soon as I get the macbook fixed and video finalized, I will make sure to post a link here in the comments so you can check it out. (Though that might be a while as I want to wait until I get all the final tweaks done, and I got some components that might take a few weeks to get here).

    I almost forgot: I wanted to mention that I went back into the screen and added a one-way refective layer (I used the stuff made for tinting windows, but did not separate the backing as I found that that introduced alot of bubbles). I definately helps when the backlight is off (one reason I want to add a switch eventually), but it is a bit more reflective than the original backing and it does dim the backlight a liitle bit as well but on the otherhand it does indeed add a increase the contrast a liitle bit…unfortunately I think the dimming caused by the resistors/hum-fix caused a liitle loss in contrast since the light blue backlight is now a little closer to medium blue, which is not the best choice for these backlight panels… If I was to do it again, I would probably go with green or yellow (though most inexpensive yellow panels seem to look lime green to my eyes… But if I could find one that looks like the yellow panel on the Boss BR-900, I would definately opt for that one). From what I read light blue also has the highest color frequency, so not sure if that is also making the hum higher as well.)

    Tray | 2016-01-17 | Reply

  21. Sounds like some really solid work! I’m not sure if there is any danger to adding series resistance to the inverter, but if so it’d probably be just danger to the inverter, and not to the panel or the rest of the synth.
    I’m very interested to see how your choice of reflective layer played out. (Of course it can be hard to tell without a point of comparison… I didn’t take enough “before” pics of my mod and I don’t have an unmodified unit around for comparison…) On my build I had considered using an iridescent material but I wasn’t sure if that would be effective. Thanks for sharing the results of your build.
    The inverter I used is the one from Backlight4you. It’s 3V compatible (which is important ’cause a lot of electronics are based on 3V supplies) but it’s actually spec’d to take anywhere from 2.2V-5V as its source (and of course a lot of older electronics like the QY use 5V supplies) – so no modification was necessary.

    tetsujin | 2016-01-21 | Reply

  22. OK– i got freaked out about all this project entails, so I opted for a gameboy backlight kit (which you can get for about $14 including shipping)
    It’s LED rather than EL lighting so it will add 1.23mm of thickness but I think it’ll fit. No need for an inverter it seems, but since I don’t need a microcontroller I’ll have to add a switch, which shouldn’t be too difficult. Thanks for the inspiration!

    Michael | 2016-05-30 | Reply

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