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Old 19th December 2019
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Prophet 600 Meltdown

I've been trying to fix what was a very small issue on my beloved Prophet 600 for the past month. Simply 1 Oscillator was out of tune. Everything else worked flawlessly. I was methodically replacing parts and testing after each. All was well as I was slowly tracking down the exact problem. That was until last night when I got the bright idea to use my multimeter to try and check/compare IC chip voltages between a good voice and the one I was having a problem with. I checked the direct voice IC chips 4016 (quad analog) and 4053 (multiplexer) for 2 voices as well as 2 small op amp chips in the S/H section. I grounded the negative probe on the metal chassis and used the positive to check the legs of the ICs. Apparently I'm an idiot for doing this and/or I accidentally caught 2 legs at once and hopefully just shorted a chip only. All was well minus the 1 Oscillator prior to this and now when I power on immediately I hear a loud screeching/white noise followed by what sounds like an Orbital CD played backwards and not in a good way. Keys respond as does the membrane panel and display. No matter what I do there is just noise in the background and all sorts of digital vomit. I'm really hoping I simply just fried one of the chips I tested and that's it. I'm in the process of putting together an order to replace the 6 total chips I touched. I'm really hoping just to get a little peace of mind in the meantime that this is likely all I did and that whatever happened didn't spread down the line to other places.

*To summarize, when an IC logic chip shorts does the damage spread or remain isolated to the chip?