On Saturday 26 January 2008 01:26:30 pm narfman96 wrote:

> I'm looking for a HD63B03YP Hitachi CPU in a 64 pin dip package. This
> is in a Yamaha DX7IIFD synthesizer and will not boot. I see that pin 15
> is not producing a reliable 500khz clock output. The waveform is noisy
> or never gets produced at all. Is there a more common sub for this CPU?
>
> Also has anyone seen a 64 pin dip socket for these? It is a high
> density style which has the pins a lot closer together than a standard
> dip.

I had some of those chips long ago, not that really helps now,
but there are sockets. They are at a 0.07 inch pitch rather
than the common .1 inch pitch.

Check the rest circuit, which might control some mode select pins.
These chips had a tendency to be flaky if reset was not clean.
Also worth checking the oscillator sections for capacitors that
have gone bad over the years. Both of those will lead to
symptoms like you are seeing.

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