Another "Cool Blue" upgrade...

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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wohali
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Another "Cool Blue" upgrade...

Unread post by wohali » Fri Aug 03, 2018 5:52 am

Hi everyone, long time lurker, first time poster.

I upgraded the display in my SY99 tonight to a "cool blue" Newhaven display. The process is tedious but not difficult. Thanks to those who have contributed great guides to this on the forum already!

I happened to have had an extra display on hand from when I upgraded my Kurzweil K2500 - it uses the exact same replacement display! And since I had fun doing that upgrade, I applied a few of the tricks from that upgrade to this one...

First, there's no need for the veloboard circuit described in the documentation. With just 2 resistors and a piece of wire, you can rework the backlight circuit on the XI138 (MIDI + contrast knob + click volume) board to do the job just fine, and reuse the original connector in the process, and remove the old backlight power supply that causes noise in the rest of the system.

Going to try to embed images, apologies if they don't work correctly. <->

Below is the surgery necessary for board XI138. Remove T31, C33, Q31, R31, and R32. Install a jumper as shown between T31 and R31. Two simple resistors in Q31 and another across T31/C33 provides the voltage division necessary to step the +5V down from the power supply to the backlight's needed +3.5V. I believe I used a ~10K resistor in Q31, and a ~25k resistor in T31/C33.

Image View image externally

For DM1, I replaced R195 with a value of 1k82. I had to experiment a bit to get the right value here. The back panel knob range for contrast is reduced with these values, but allows a little bit of adjustment.

Finally, while I was inside the machine, I added a grounded power lead:

Image View image externally

The audio output now sounds a lot cleaner than it used to, but I don't know if it's because of the removal of the inverter for the backlight power supply, or adding the grounding that did it.
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Re: Another "Cool Blue" upgrade...

Unread post by Saul » Fri Aug 03, 2018 9:07 am

Hi wohali Welcome to yamahamusicians.com :)

Great first post! Thanks for sharing the info and the images. All these things make life a LOT easier for those searching online for details on the SY99 display replacement.

I believe it is the inverter that causes the noise on the SY77 and SY99?
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Re: Another "Cool Blue" upgrade...

Unread post by Derek » Fri Aug 03, 2018 7:41 pm

Hello, welcome and congratulations.

The inverter whine should not end up on the outputs, but you do hear it in the studio, and it is annoying, so well worth getting rid of.
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Re: Another "Cool Blue" upgrade...

Unread post by Saul » Fri Aug 03, 2018 8:39 pm

That's constant whine from the inverter was the first thing I noticed when I had my SY77. It was the first time I had come across such a thing on a keyboard. I didn't keep it long enough to fix it and I don't think the person who had it after me fixed it either. It's annoying but one of those things you get used to.
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