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Prophet 600 troubleshooting....Digital Side.

2008-04-19 by Brendan Haley

Is there anyone out there that has experience troubleshooting problems with the Prophet 600, specifically the digital side of things?
I have a broken Prophet 600 that powers up. I get no sound out of it, and "gibberish" on the numerical readout. With the standard eprom in it it doesn't even really respond in any discernable way to pressing any of the keypad numbers.
I have the diagnostic eprom from Wine Country, which also does not act as expected although with the Diagnositc chip in the keypad does produce reproducable results, or in other words, the "gibberish" changes in a systematic way when I press the membrane keypads.
So I am assuming that whatever is wrong with this is mostly on the digital side (I think....). Of course, I am not so good with digital stuff (though I do have a logic probe, and a scope, etc.)
Any thoughts, or anyone out there willing to give me some hints, or maybe tell me some more directed things to try?
Also, is there any way to kind of "bypass" the digital side, to just get a sense that the "analog" side is working properly (I see the waveforms I think I should see on the appropriate pins on the Oscillator chips so I THINK they are good....
-brendan

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