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

[w.james.meagher at gmail.com]

> A "square wave" is never going to be perfectly square, particularly when you're dealing with "real world" components.

I figured that was the case but had been so impressed by the true squareness of the waves I was reading from the voice sections that these imperfections from the CPU board stood out.

>> Is there anything else that could be loading the pin down?

Ahhh... Sadly I don't know enough about what I'm doing to actually answer that question! What I have noticed is that pins 3 through 8, which should all show voltages between 2.1 and 2.7 are all up nearer to 5v. Issue is not present on the other 4 ICs, and those currents are all coming from one source which meters out as it should: 2.1 to 2.7V.

> Flattish.  Remember, it's got to go through a diode first, so there's some voltage drop there.  What's the voltage across the power pins of the memory chips?

I'll check that as soon as possible. Tomorrow is anniversary #7, so it's a tad unlikely I'll get to spend too much time in basement...

> Have you tried replacing the coin cell with something like two AA batteries in series?  That's what I do when I'm replacing them, and they last 

No actually, I've never done this. Last forever huh? I like the sounds and simplicity of that!

> Well, you may as well get them but I don't like to replace parts that I don't have to.  The more you do, the more you risk damaging the board...

Yeah, I don't intend on installing them unless the new battery fails to solve the issue. My desoldering skills are still a work in progress so I'm not too anxious to tackle anything with lots of pins if I don't have to.

Many thanks for taking the time to advise me.

James


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