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

[Gordon JC Pearce]

On 14/07/12 23:09, james meagher wrote:

> 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.

It's actually probably supposed to provide a squarewave to some circuit. 
  The fact that it shows as 2.1V is more of an artifact of the meter 
used to read it.  Check with an oscilloscope.

>
> 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

It's a pretty generic programmable timer chip, used in loads of things.

> 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.

Have you got a good reason for suspecting they are faulty?  Unless 
you're *certain*, leave them alone.  If they are faulty they will most 
likely get red hot within seconds, from past experience.

-- 
Gordonjcp MM0YEQ