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Periodic MB-SID freakout


th0mas

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Hi all!  Long time no talk.. I haven't forgotten about everything and everyone here though.  I've moved to doing most my development on AVRs due to the GCC port availability.

I *finally* after multiple years have finished my midibox SID.  It took 2 SID chips, 3 recasings, 2 resolderings, but I finally have a unit that for the most part functions.. the SID was my first DIY synth and through making it and remaking it, it provided me the basis to go on an make a number of microcontroller-based AVR projects from scratch as well as build a x0xb0x :).

Anyways, my SID does this weirdo thing.  Peridically, maybe after 10 minutes use, it will sound "grounded out", and the contrast on the LCD will freak out so it appears that both lines are completely solid on the LCD.  If I leave the unit on it will go away after awhile - it used to take a long time like a half hour but recently the glitches are shorter, like 20 seconds.  If I turn it off and on it doesn't immediately fix it.  Could this be a faulty/tempermental SID chip?  I'm looking for someone to say "yup, I had that problem, faulty SID".. if no one does I know how to troubleshoot most everything else but I'd rather not have to start seperating my modules again to hunt for the problematic module.

Thanks!

Tom

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I would check to see how hot your regulators are getting before blaming your SIDs, particularly if it is after it's been on for a while. I generally tape my temperature probe from my multimeter to the tab of the regulator with some electrical tape. My experience has been that if it gets around 60C it could shutdown. This is by design to protect the regulator and can be avoided by adding a heatsink to the regulator.

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I will give that a shot, it might be my regulator on my SID module.. however whats weird is that it'll freak out, then come back and work for hours, then freak out, then come back and work for hours.. I have a heat sink somewhere around here I can try to attach too I think

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I third the regulator. No way it's the SID. :) I don't think ICs temporarily go into high current drain mode... it is thus more likely the supply is failing, which means the regulator is most likely the problem. Maybe you're supplying the 7805 with a high voltage like 12V and expecting it to shed 7V at 500mA = 3.5 watts of heat.

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thanks everyone!

Looks like you're in the right area.. while the regulator is fine on the SID module, i found out that my power supply intermittently supplies 8.5v instead of 5v!!  I'm using a commodore diskdrive AC adapter which supplies both 12v and 5v.. looks like it's fried.  I can't blame it, it's been through a lot all these years :D

edit: andd when they tell you "no user serviceable parts inside" they mean it. The whole thing is encased in resin, well off to craigslist and ebay :D

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