SY99 ROM version and AT question

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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SY99 ROM version and AT question

Unread post by SYfi6 » Tue Nov 28, 2017 3:06 pm

New to this forum. Seems very knowledgeable about this old synth. Looking forward to share my experience with SY series.
My SY99 is:

Main ROM: Version 1.40
SEQ ROM: Version 1.20

Should I upgrade it? If so than how?

Also, test mode revealed that I can't get higher value for Aftertouch than 62 on all keys. It should get up to 99.
What that symptom tells you? Is it an easy fix? hard fix?
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Re: SY99 ROM version and AT question

Unread post by parametric » Tue Nov 28, 2017 5:03 pm

Welcome to the Forums SYFi6,

I don't have a 99, but IIRC - Those Roms look to be late versions . . .

The AT thing I think is a known issue and has been discussed in here before -

I'm sure an owner will be along shortly to discuss that with you . . .


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Re: SY99 ROM version and AT question

Unread post by Miks » Tue Nov 28, 2017 5:33 pm

Hi SYfi6,

welcome to the Yamaha Musicians Forum (Y)

You may want to read this (entire) thread:


Latest Main ROM version is 1.57 (depends on your CPU!)
Latest SEQ ROM version is 1.30

As for the AT: here you can find an AT repair pdf - including the adjustment of the AT board (two trimmers). Maybe it helps... :wink:

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Re: SY99 ROM version and AT question

Unread post by DrSynth » Sun Dec 03, 2017 12:57 am

The only (functional) reason to upgrade is if you wish to add additional Sample Memory boards. Main ROM Version 1.57 fixes various bugs in saving and loading large numbers of samples. The Seq ROM version 1.30 fixes a very obscure bug you're not likely to encounter in the Sequencer.

As Miks mentioned, you must upgrade the CPU along with the Main ROM for version 1.57. This can be done as the CPU's are available and can be burned, but based on personal experience there are a few caveats - the quality of the CPU's available is very inconsistent.

I can successfully burn 4 out of 5 CPU's I get from China, but of the 4 good burns only 1-2 of them will typically make complete contact when placed in the CPU socket. It can vary depending on the condition of the socket of your SY99 -- for example I have one SY99 where every CPU I've made works fine, and other SY99's where only 1 or 2 of the CPUs make proper contact and will work.

So you could invest as little as $26 to close to $100 in CPU's to get one to work in any particular SY99. So if you don't need it for the handling of samples, don't bother.

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