Help find an old ICs datasheet or equivalent.

[Brisance]

Any help appreciated. from function it seems it is something like a decade counter from tghe 70's

[~arph]

Might help if we had the whole schematic

[Brisance]

It's from an eminent 310's drum synth, I extracted the page from a pdf I found online( the picture in the OP is the one I made from the paper version ) Here: http://www.filedropper.com/schem

Basically I want to understand it's drum sequencing and hack it so I can access it externally so I can build a manual trigger and a midi input for it.

[anotherjim]

It could be an 8bit mask programmed ROM or EPROM - even a fusible link type. It's an early type chip whatever, given the 15v supply (and is it -15v?). The 8 left facing wires to a resistor network could form a DAC. A lot of early drum machines used 8bit wave-tables like that.

[Brisance]

Thanks! The main question however is, how does it handle it's outputs, does it just pull them down? is it an open collector(which I would prefer, easiest to hack probably)

[Digital Larry]

The inputs from the left hand side say "rhythm selector" and so I vote for this thing being a ROM pattern generator which goes off and triggers the various drum sound sub circuits in accordance with some guy in a lab coat's concept of "groove".  Boom chicka chicka.

I think it probably has totem pole outputs.  But it's just a guess.  I don't see pull up resistors in some of the drums sound subsections, and there are series diodes in some of those trigger lines, which would tend to indicate "only conduct when input is pulled down".

[Brisance]

Update, I opened it up and took a nice picture, the good news being, that it's in a socket, so hacking will be simpler and leaves me the possibility to switch between the original chip and whatever I connect it to( series of switches to trigger sounds manually mostly and hopefully a MCU powered MIDI input. )

Here it is in its glory, surrounded by tropical fish and carbon comp.

[~arph]

Cool, like the borg..  I don't see any carbon comp though..

[Brisance]

arent those oldschool looking resistors carbon comp? maybe not then

[Ice-9]

arent those oldschool looking resistors carbon comp? maybe not then

Carbon film resistors