[sdiy] Yamaha TX81Z FM chips

[Richard Atkinson]

On Thu, 28 Feb 2002, Maciej Bartkowiak wrote:

> Richard,
>
> I just opened mine to have a look for the synth engine chip as well as to
> see,
> if the horribly humming power transformer is replaceable and if there is
> some
> space to fit an analogue filter in (my plan).

Thanks very much! I'm extra-ordinarily grateful!

> There is one DIP24 YM2414B and I think that's it. There is a YM3012 small
> DIP16 denoted as IC12, located close to 2 x JRC6046 +  JRC6074 + JRC6253
> (looks like output buffers), and I suspect the 3012 is a DAC.

Yes, YM3012 is a stereo serial DAC using floating point representation (10
bit mantissa, 3 bit exponent).

> There is a 5564 from Toshiba (a SRAM for storing patches, I guess) and a
> socketed 27512. This may be a factory patch set, which suggests a
> possibility
> to reprogramme these - great news, if I only knew the encoding scheme.

Curious. FB-01 has two 8K SRAMs.
>
> Oh, yes, there is a HD63B02XP (possibly a controller?)

Whereas FB-01 uses an ordinary Z80. I wonder why Yamaha shuffled the
design around so much. I always thought these two modules were supposed to
be very similar.


Richard