[sdiy] Prophet 5 rev2 conundrum

Gordonjcp gordonjcp at gjcp.net
Thu May 4 01:13:44 CEST 2023

On Wed, May 03, 2023 at 05:27:11PM -0400, NT wrote:
> from his last message it looks like something is preventing any movement on
> the tune data bus so it never actually activates the 4051s. From the
> firmware side the behavior would be the same as if the board isn't
> installed (or tune init fails). Knowing that the tune bus works under
> normal circumstances makes it stranger that it's dead when tune should
> initiate.

That is a bit odd - literally not a flicker, even the briefest of flickers, on the mux address pins?

I wonder, then, if all is well with the comparator? I'm always a bit suspicious of resistors up around the megohm range, having found them wandering off skywards with age.

How do the DC conditions around the 311 look, compared between boards?


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