[sdiy] Question regarding IC replacement in Akai AX80 (was: Akai AX80 weird PWM behaviour . . . )

[james meagher]

Question about finding compatible replacements for some older ICs . . .

I verified last night that there's actually nothing wrong with the
circuitry on the Voice Board causing DCO2 on Voice 4 to not make a
sound. I verified this by flipping the two cable harnesses that run
from the CPU Board the Voice Board (one of the cable harnesses is for
voices 1-4 and the other 5-8). Sure enough DCO2 on Voice 4 worked just
fine when the CPU thought it was Voice 8 . . . And DCO2 on Voice 8
wouldn't make a sound. So I traced the problem back to Pin 13 on IC22
on the CPU board. This pin should be providing 2.1V to the Voice 4
DCO2, but is only mustering 0.1V. I checked all the other pins on this
IC and noted a few other incongruities with the other four ICs that do
the same job.

I'm going to replace this IC22 which is listed in the AX80 parts list
as UPD8253C-2. I've searched D8253C-2 and come up with some hits from
companies I've never ordered from and eBay of course. What I don't
know is if there is a more readily available alternative I should look
at instead? By what method should I go about determining this for
myself so I don't need to post here every time I'm looking to replace
an old IC? I'm also thinking about replacing my two RAM chips,
D446C-1.

Cheers,
James