The dark side of the SY99 (black LCD mod)

The Yamaha SY99 is a synthesiser combining frequency modulation synthesis (branded as Advanced FM) and sample-based synthesis (branded as Advanced Wave Memory 2) and the direct successor to Yamaha's SY77/TG77

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The dark side of the SY99 (black LCD mod)

Unread post by EX5_etc » Fri Jan 18, 2019 3:24 pm

Time flies. It has been almost 13 years, since March of 2006, that I did the first BLUE display modification on the SY99 and posted the results on ex5tech.com that is now out of commission. The blue display has worked fine over the years but then I have used the keyboard so little that the display is expected to work fine anyway.

A few months ago I thought about upgrading the display again. Even though the BLUE display looks nice, it does not match well its “surroundings” as far as color is concerned. A VFD-type display would be the best option but they don’t come in the exact dimensions, they are thick and they consume a lot of power. Such a display would put a higher than desired load demand on the SY99 power supply that has been aging gracefully mainly due to the high quality Japanese capacitors that Yamaha used at the time.

The only option was a white-letters on black-background LCD unit from EastRising Tech Co, also known as BuyDisplay.com from eBay and other sites. I had used a 2-line white-on-black character LCD from them several years ago but I was not happy with the results. It looked more purple than black. The company told me at the time that they were trying to develop a better polarizer film that could make black look more black than purple. It was not an easy issue to tackle; they had to cut some of the light spectrum without reducing the brightness of the desired colors too much.

Technology moves of course and thus I decided to give them another try. The 240x64 display presented here is model ERM24064DNS-1 and costs $31.60 on eBay (S/H included). It cost me only $26.86 due to a 15% coupon that eBay applied when I bought it. The ERM24064DNS-1 is one of the 15 different versions of 240x64 displays (ERM24064-1 series) EastRising makes. Built quality appears to be very good, instructions and sample code for various projects are provided free by the company and they are also pretty good.

What is not so good is a change they made (with good intensions) on the LCD circuit that can cause problems in some SY99 keyboards because Yamaha “had to” have it their way when they designed and built that famous keyboard. They never assumed of course that DrF and others would be messing around with their keyboards 25 years (or so) after they put them in the market.

Before we go to the specifics we need to take a brief trip down memory lane. In March of 2006 I used a graphic LCD by Emerging Display Tech Co, the EW50340BMW, 240x64 pixels, white-letters on blue-background. I published very few details on ex5tech.com because it is not an easy modification to attempt. You have to remove almost the entire guts of the synthesizer to reach the area where the display is. I counted about 120 screws that I had to remove, starting from the cover and going all the way down to the 4 screws of the LCD itself. And then you have to put everything back, correctly. It looks something like this:

SY99_BLK_P01.jpg
Several SY99 users decided to go for it. Along with several SY/TG77 users. Derek made a nice detailed guide to help others and the rest was history as the saying goes. That blue display was not available for too long. Others became available and some users took it upon themselves to try with different blue displays and post about their experiences.

If we take a look at the pinout arrangement of the original blue EW50340BMW we see the following classic layout:

SY99_BLK_P02.jpg
Nothing special about it, we only use the first 20 pins of the connector and then solder to pads “A” and “K” the 5 V wires that once supplied the inverter board of the original LCD (it required perhaps 100 V for its backlight).

We now take a look at the pinout arrangement of the ERM24064DNS-1:

SY99_BLK_P03.jpg
At first it appears to be the same, someone would say. But a more careful look reveals that pin 20 is not a not-connected (NC) option as in the original blue display, it is a negative voltage supply to be used by this LCD to control its contrast. On the test bench that pin supplied -14.30 V that I used with a demo board for LCDs made by Sure Electronics to control graphic LCDs (the demo board is not available anymore).

EastRising decided that instead of relying on external circuitry to supply the negative voltage for their displays they would add a negative voltage generator on the LCD board. In order to keep the pin compatibility as it was and offer a drop-in replacement, they used one of the two NC pins to output that negative voltage, pin 20. They thought that since it was a NC pin in all original designs there would be no problem if anyone wanted to simply drop-in their newer ERM24064DNS-1 displays and use the negative voltage supplied to pin 4 of the display by the device they were upgrading/repairing instead of using the built-in negative voltage generator on pin 20.

That assumption may have been valid, but not for Yamaha. If we take a look at the service manual of the SY99 we see something disturbing at the tip of the red arrow in the following picture:

SY99_BLK_P04.jpg
They decided to tie together pins 19 and 20 on the main board that carries connector CN111, the connector of the ribbon LCD cable. What is the big deal with that? Pin 19 is tied to either +5 V or 0 V in order to choose the font size of the LCD. If we drop-in the newer display without any care, we short its -14.30 V to either 5 V or 0V. That means trouble because we will take out some of the LCD circuits. And who knows how the synthesizer will handle those voltages. The negative voltage generator on the LCD is not a circuit that supplies high current to potentially damage the SY99 but we have a problem and it is better to solve it before it becomes a bigger one.

Being who I am, in other words a non-believer, I decided to check on this. A continuity test on CN111 between pins 19 and 20 showed no continuity in my SY99. In other words, go figure what Yamaha was thinking or doing. The service manual shows a connection between pins 19 and 20, the synthesizer actually has none. But it could be that some newer or older versions of the DM1 board have pins 19 and 20 tied together. Yamaha made changes to the various versions of the SY99 over the years, including the main CPU, some memory chips and who knows what else.

On the test bench I noticed that in order to achieve black color that looked mostly black on the LCD screen I had to consider another parameter beyond the negative voltage of pin 4. The ERM24064DNS-1 manual states that 5 V can be applied directly to pads “A” and “K” causing up to 140 mA of current to pass through the backlight LED of the display. It made the LCD too bright. My measurements showed that the view was better if only 40 mA passed through the LED causing a 3.36 V drop across pads “A” and “K”.

I tested the LED with the 100 mA version of a 3.3 V voltage regulator (it looks like a small transistor), but it did not give me the 40 mA I had hoped for. It needed over 6 V in its input to give me that current. I measured the 5 V supply of the SY99 and found it to be only 4.93 V. Thus I connected a 41.2 ohm mil-spec resistor in series with the backlight LED. The resistor does not have to be mil-spec, I happened to have it around for years and it worked perfectly for my “black background color” requirements. Since the resistor will be consuming no more than 65 mW of power, the 250 mW version I used was more than enough.

Before I go over the next few pictures showing how I took care of the issues mentioned so far I must also mention that when I put the SY99 back together I noticed (after about 95 screws, the rear cover was still off) that the new black & white display did not look as good as it did during my bench tests. I measured the LCD contrast voltage on pin 4 of connector CN111. It would not go below -8.715 V when I turned the contrast potentiometer on the rear of the SY99. The ERM24064DNS-1 needed a value between -7.0 V and -7.3 V in order to have a decent white-letters on black-background view. I thought that if I had to go back in and remove everything in order to fix the problem I better not met any living person for the next few hours of the day.

Instead of doing something bad (with a hammer) to the keyboard or to anything else in the house I checked the service manual that was left in another room. I had put the SY99 back together using only my memory. The manual had been left out of sight on purpose. To the youngsters of the forum that may be laughing about this I must say that when you get older the brain is the first thing to go. I was testing my brain as I was re-assembling the SY99; I proved to myself that I still have one that works. I had put this monster of a synth back together without help, for the second time in my life. Anyhow, without going through all the details, the LCD contrast circuit of the SY99 looks like this:

SY99_BLK_P05.jpg
On the left side we see the theoretical version of the circuit. It is a variable voltage divider with preset limits, for those that know what I am talking about. In the middle we see the actual circuit as measured on my SY99. When the potentiometer was all the way down it provided -8.715 V to the LCD. In order to drop that voltage more I had to change the voltage division ratios, or in simple terms, I had to lower the value of resistor R196.

This was one of several options I had; I could have also replaced the potentiometer, or R195 on the DM1 board, or R196 on the DM1 board. None was a valid option because it required serious “surgery” to the SY99. At that point the synth was assembled back together and there was no way I would take it apart again. I calculated that if R196 dropped to about 2200 ohms the circuit would provide to the LCD the voltages I expected to have. The modified circuit on the right side of the picture shows that a 5100 ohm resistor was soldered in parallel to R196. Since the measured value of the added resistor was 5020 ohms, the total of the two in parallel was 2195 ohms. That dropped the contrast voltage on pin 4 of connector CN111 down to -7.05 V, more than enough to have the right B/W colors on the display.

The following picture shows the rear side of the B/W LCD before any modifications were made to it. It is a fresh LCD made in 2018 as the date label shows. It is also 1 mm thinner than the blue LCD I had used in the original modification.

SY99_BLK_P06.jpg
The LCD requires some preparation before it goes into the SY99. Below we see it with the 41.2 ohm resistor (labeled 41R2 on the right insert) soldered on the “A” pad. On the left side we see the right angle connector I used. Pin 20 is missing, on purpose. You simply pull it out before you insert and solder the connector on the LCD. You don’t have to use a right angle connector, one with straight-up pins should also work. By not using pin 20 that carries -14.30 V we eliminate the issues I mentioned earlier, if by some chance your synth has pins 19 and 20 tied together. Pins 21 and 22 are not used at all, since we supply power to the backlight LED through pads “A” and “K”. Acetone was used to clean residual flux from soldering. Attention to detail, the story of my life and unhappiness.

SY99_BLK_P07.jpg
The next picture shows the LCD seated inside the SY99. The ribbon cable is attached. On the left side the blue square shows the 3-pin connector that once powered the high voltage inverter. It was soldered to the LCD to power the backlight LED. The yellow wire carries 5 V, the two white wires are tied together to the ground, on the power supply board. The yellow wire is soldered to the current limiting resistor, so it is in series with pad “A”. Something I forgot to do in my SY99 was to solder both white wires on the “K” pad. That would have put them in parallel, thus reducing the resistance of the long wires to the power supply. I would have perhaps gained a few mV. Too late to fix it now, but it is not a big problem.

SY99_BLK_P08.jpg
The re-assembly of the SY99 took longer than expected because several screws had lost their grip and needed replacement. Additionally I checked the backup coin batteries. They were still holding enough power with their voltage measured at over 3 V. I had replaced them at least 5 years ago I think. Both were made in Japan by Sony and Maxell. That should have been a clue. Try Chinese and see what happens.

When everything was back in place and tested with a brief power on, I did some “surface surgery” to alter the voltage divider that supplied the negative voltage to the LCD. The following picture shows the area inside the yellow square where alteration was needed. The ribbon cable to connector CN101 was removed on purpose, so that a better picture could be taken. Connector CN111 of the DM1 board can be seen on the right side and the main CPU (version 1.50) on the bottom left.

SY99_BLK_P09.jpg
The final picture of the internal modification shows tiny resistor R195 on the right yellow square. It should be left alone. Tiny resistor R196 on the left yellow square has a big brother soldered in parallel to it. That is the 5100 ohm resistor I mentioned earlier. I have those tiny resistors somewhere in my workshop but I could not find them. I simply used a 250 mW resistor with a nominal value of 5100 ohm because that was the smallest one I had, in terms of power handling.

SY99_BLK_P10.jpg
Below we see how the SY99 looks with the new LCD in place. The contrast must be adjusted depending on the seating position of the user if a darker black color is desired. The closer to the synth you seat, the more “true” white-on-black color contrast you see.

SY99_BLK_P11.jpg
SY99_BLK_P12.jpg
That is all there is to say about the latest LCD modification. You may try it if you wish on your SY99, SY77 or TG77. Feel free to report back here with your experiences. Ask questions if you have any. I’ll try to answer them as time permits.

Best regards,
DrF
Last edited by EX5_etc on Sat Jan 19, 2019 12:21 am, edited 3 times in total.
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Re: The dark side of the SY99 (black LCD mod)

Unread post by EB5AGV » Fri Jan 18, 2019 3:46 pm

Wow, it looks great! (Y)

I will probably go this way with my second SY77, which needs some serious work (switches, pots, DM1 board, display, ...)

Thanks for sharing! :clap:

Jose
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Re: The dark side of the SY99 (black LCD mod)

Unread post by parametric » Fri Jan 18, 2019 6:17 pm

Outstanding Work Sir!

para
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Re: The dark side of the SY99 (black LCD mod)

Unread post by Derek » Fri Jan 18, 2019 8:48 pm

Hi, DrF

That actually looks much better than Cool Blue (which looked much better than the stock display), that I may have to get a few displays for my TG77 and SY99. I need to replace the PCB switches on both at some point as they are getting pretty sticky on both, so whilst taking them apart I may do the displays as well.
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Re: The dark side of the SY99 (black LCD mod)

Unread post by EB5AGV » Fri Jan 18, 2019 9:41 pm

Derek wrote:
Fri Jan 18, 2019 8:48 pm
Hi, DrF

That actually looks much better than Cool Blue (which looked much better than the stock display), that I may have to get a few displays for my TG77 and SY99. I need to replace the PCB switches on both at some point as they are getting pretty sticky on both, so whilst taking them apart I may do the displays as well.
One hint on this, as I did it a year ago: use ONLY good quality switches. I got some OMRON ones from Farnell. It is false economy to use cheap chinese clones. Trust me, I have used that kind of switches for decades.

Jose
Jose Gavila

Yamaha DX7, TX81Z, DX11, 5x SY77, TG77, SPX990, SY85, A3000, AN1x, EX5, EX5R, EX7, MOTIF RACK XS, DGX660, Genos (and 1992' FJ1200 :mrgreen: )

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Re: The dark side of the SY99 (black LCD mod)

Unread post by EX5_etc » Sat Jan 19, 2019 12:01 am

parametric wrote:
Fri Jan 18, 2019 6:17 pm
Outstanding Work Sir!

para
Thanks for the kind words parametric. Since the post will be around for others to try I decided to do better than I did the first time. Back then I posted just a picture of what to do with the blue display and one showing how it looked.

This mod is a bit more adventurous than the first one. So the more information I include here the better it is. As always, anyone trying this, please keep in mind that if you damage your synth it is your problem not mine.

DrF
Motif XF6, DeepMind 12D, MicroArranger, MicroKorg S, SY99, SY85, QS300, PSR1000, WX5, EX5R, A5000, TG500, TG55, RM50, QY700, QY100, QX5FD, MDF3, MJC8, EMX2, YDP2006, REV500, EMP700, EQ500U, MCS2, AW16G, Axiom Pro 49, AKAI Pro Advance 49, Arturia KeyLab mkII 61, and a few other things by Behringer, Evolution, Philips, Tascam, Technical Pro, Yamaha, etc, etc,... I wish I had time to use all this stuff; I am not even pro. :-)
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Re: The dark side of the SY99 (black LCD mod)

Unread post by EX5_etc » Sat Jan 19, 2019 12:10 am

Derek wrote:
Fri Jan 18, 2019 8:48 pm
Hi, DrF

That actually looks much better than Cool Blue (which looked much better than the stock display), that I may have to get a few displays for my TG77 and SY99. I need to replace the PCB switches on both at some point as they are getting pretty sticky on both, so whilst taking them apart I may do the displays as well.
Hi Derek.

It does look better but I emphasize for one more time, not from every angle. As soon as you move a foot away from the synth while you play with it, that black color washes out and turns into bluish. The pictures I posted might not show this clearly: the left side of the LCD is more dark than the right side. It must be something with the LED below.

As far as I recall one big issue LCD TV manufacturers had and perhaps still have, was accurate reproduction of black color. It is not as easy as it may seem. This LCD is nowhere near TV quality but still, the issue is there.

By the way, when you get a chance, attach to this thread a link to your guide so that anyone trying the mod will have access to your information as well to avoid damaging their synthesizers.

DrF
Motif XF6, DeepMind 12D, MicroArranger, MicroKorg S, SY99, SY85, QS300, PSR1000, WX5, EX5R, A5000, TG500, TG55, RM50, QY700, QY100, QX5FD, MDF3, MJC8, EMX2, YDP2006, REV500, EMP700, EQ500U, MCS2, AW16G, Axiom Pro 49, AKAI Pro Advance 49, Arturia KeyLab mkII 61, and a few other things by Behringer, Evolution, Philips, Tascam, Technical Pro, Yamaha, etc, etc,... I wish I had time to use all this stuff; I am not even pro. :-)
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Re: The dark side of the SY99 (black LCD mod)

Unread post by EXer » Sat Jan 19, 2019 1:26 am

That white letters on black background LCD display matches the black and green “surroundings” (as you say) very well.
Last edited by EXer on Sat Jan 19, 2019 3:26 pm, edited 1 time in total.
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Re: The dark side of the SY99 (black LCD mod)

Unread post by Derek » Sat Jan 19, 2019 9:05 am

EX5_etc wrote:
Sat Jan 19, 2019 12:10 am

By the way, when you get a chance, attach to this thread a link to your guide so that anyone trying the mod will have access to your information as well to avoid damaging their synthesizers.

DrF
Here you go: My Guides Page has guides for
  • SY77 (based on DrF's original SY99 work shown on EX5Tech)
  • SY99
  • TG77
Whilst details around the display and what you need to do there will change, the basic details for disassembly and reassembly remain the same.
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Re: The dark side of the SY99 (black LCD mod)

Unread post by ledan » Sat Jan 19, 2019 2:25 pm

A very nice guide. Thx indeed :)

A question: when you write that R195 should be left alone, would that contradict the (variable) resistor added to R195 in the guide linked by Derek (or are they not related in that sense given that you do other modifications as well)?

I installed the black/white display in my TG77 a couple of months ago and i (following Dereks guide) put a variable resistor on R476 to adjust the output (a 2k - 10k variant) and it works quite well (but the lightning is a little bit uneven imho). Would R476 (TG77) == R195 (in the SY99/77)?
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Re: The dark side of the SY99 (black LCD mod)

Unread post by Derek » Sat Jan 19, 2019 3:13 pm

Don't forget the upgrades describe different display technologies over the years and they have different needs. If you are doing the mod proposed here, then DrF's guidance should be extant. The purpose of providing my guides here are to show you how on earth to get to the display in an SY99! :D
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Re: The dark side of the SY99 (black LCD mod)

Unread post by EX5_etc » Sat Jan 19, 2019 10:46 pm

I think Derek put it in the right perspective: the links to the guides are there so that other members wanting to try this can get to the display.

I have taken completely apart the PSR1000 and the SY85. Almost entirely apart the EX5R (front panel is a real bitch), the A5000, some of my controllers and various other Yamaha modules I have. The SY99 tops them all in terms of complexity. It is not a task for everyone to take that beast apart and then put it back together. It still amazes me how on earth they were able to design it with many levels of hardware stacked in the way they did, how they formed the various metal frames, how they calculated the number of screw holes to drill, etc. So, one more time, anyone trying this with the SY99 must be careful and completely free of alcohol :D when attempting the mod. If you damage your synth it's your problem.

Having said that we can now talk about the TG77. A couple of snapshots of the contrast circuit:

TG77_LCD.jpg

If we combine those two snapshots together we end up with this:

TG77_CIR.jpg
TG77_CIR.jpg (30.12 KiB) Viewed 650 times
The main voltage divider consists of R475, VR301 and R476. It's not working alone because another voltage divider consisting of R102 and R103 is tied to it. In my opinion there is no reason for R102 and R103 to be present. Unless Yamaha knew that VR301 could fail and instead of having a floating wiper coming out of VR301 with no "control" voltage they wanted to have a backup "minimum acceptable" voltage for the LCD contrast, provided by R102 and R103. That way the display would be usable (partially readable) but without any control of its contrast.

Since the values of R475 and R476 are lower, that side is the dominant one and we can assume (even though it is not a very valid assumption) that it is the side that PRIMARILY controls the LCD contrast.

So, what is there to do? Check the voltage on both sides of VR301 with respect to the ground. If the two values fall within the limits I describe above then your circuit is fine. You will have to consider altering your backlight LED brightness. If, on the other hand, those two values are not within the limits I measured, you must alter R475 or R476 accordingly.

Let us know how it works out for you.

DrF
Motif XF6, DeepMind 12D, MicroArranger, MicroKorg S, SY99, SY85, QS300, PSR1000, WX5, EX5R, A5000, TG500, TG55, RM50, QY700, QY100, QX5FD, MDF3, MJC8, EMX2, YDP2006, REV500, EMP700, EQ500U, MCS2, AW16G, Axiom Pro 49, AKAI Pro Advance 49, Arturia KeyLab mkII 61, and a few other things by Behringer, Evolution, Philips, Tascam, Technical Pro, Yamaha, etc, etc,... I wish I had time to use all this stuff; I am not even pro. :-)
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Re: The dark side of the SY99 (black LCD mod)

Unread post by EB5AGV » Sat Jan 19, 2019 11:07 pm

On the same line, to help people get into the work of arriving to the display, I add a link to my WEB page regarding an SY77 repair work (which I guess should be pretty close to the SY99). There you will find a ton of pictures:

http://jvgavila.com/Yamaha_SY77_repair.htm

Jose

PS: I will add soon to my page my work on two other SY77 :wink:
Jose Gavila

Yamaha DX7, TX81Z, DX11, 5x SY77, TG77, SPX990, SY85, A3000, AN1x, EX5, EX5R, EX7, MOTIF RACK XS, DGX660, Genos (and 1992' FJ1200 :mrgreen: )

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