[sdiy] Crumar DS2 Problem

Julian Schmidt elfenjunge at gmx.net
Mon Aug 25 18:49:08 CEST 2003

Thanks for the long answer!

I tried cleaning the contacts, but with no succes.

today i received the new IC's for the Keyboard Control PCB and now the 
crumar works 100% ^^

you won't see me outside the next days ;)

Am 21.08.2004 um 22:26 schrieb WeAreAs1 at aol.com:

> In a message dated 8/21/04 11:33:30 AM, elfenjunge at gmx.net writes:
> << so i'm gettingt
> some new IC's for the adsr board as well, since its only a few bucks
> more on my order list an all ic's in the synth have sockets ;) >>
> All the IC's are in sockets???  OK, that's useful information.  Hey, 
> before
> you rush out and buy a bunch of parts, why don't you try removing the 
> existing
> parts from each socket and carefully cleaning their pins, as well as 
> cleaning
> the sockets themselves?  A very common failure for instruments of that 
> vintage
> (late 70's to mid 80's) is parts not making good contact in sockets, 
> usually
> due to oxide buildup on the IC pins.  Ask anyone who has repaired a 
> lot of
> Oberheim OBx and OBxa and/or Prophet V synths.  When I deal with this, 
> I will
> first make sure that I'm properly grounded with an antistatic wrist 
> strap, then I
> take out the chips and gently scrape both sides of the pins with an 
> Xacto
> knife.  You will immediately see the difference -- the metal of the 
> pins, which
> before was dull and gray, will now be nice and shiny.  I also apply 
> just a tiny
> amount of Cramolin onto the socket itself, then I work the IC in and 
> out of
> the socket a few times to let the IC's pins kind of scrape/clean the
> wiper/receptacles of the sockets (this is all done with the synth's 
> power turned OFF, of
> course).  This should also be done with the pins and sockets of any 
> and all
> multipin connector cables that are found in the instrument.  Really, 
> try this
> before you throw a bunch of new parts in there.  It's far more likely 
> that you
> have a bad contact somewhere than you having an actual bad chip, and 
> if you
> wait to do it until after you start replacing chips, then you have to 
> deal with
> the question of whether the new chips are actually good (yes, that can 
> be a
> real concern).
> As a synth repair tech with over 25 years of professional experience, 
> I would
> estimate that greater than 75% of all electronic repair problems are
> electromechanical in nature, and not a result of bad electronic 
> components.  I'm
> talking about things like oxide on IC pins, cracked or "cold" solder 
> joints, broken
> wires, bent pins, dirty switches and pots, etc..   This is especially 
> true
> these days in the era of surface-mount, oven-soldered components.  
> Remember that
> next time your new digital fizzbang virtual modeling synth goes 
> belly-up --
> It's probably not a bad 144-pin DSP chip, it's the crappy factory 
> soldering job
> they did on that chip, or another one somewhere on the main board.  
> Believe
> me, there's something very satisfying about reviving a dead Nord Lead 
> or Yamaha
> FS1R with just a soldering iron and some liquid solder flux (and a 
> steady
> hand...).
> People are always so eager to replace good components when they try to 
> repair
> their own synths.  Folks, IC's and transistors are not like brake pads 
> or car
> tires.  In a properly designed system, they don't wear out from normal 
> use,
> and they don't (usually) simply fail after 20 years of faithful 
> service.  I am
> actually more leery of new parts, because unlike the old parts that 
> have been
> happily humming away for years, they don't have a *history of 
> reliability*.
> Think about that for a minute.  Unless logic and all evidence points 
> you
> directly to a bad chip, always suspect something else first -- 
> something less sexy,
> something mechanical in nature.
> This is not to say that IC's and semi's never go bad.  They do, but 
> far less
> often than most people think (and passive components go bad even LESS 
> often).
> Often, the less experienced tech will try replacing an IC and be 
> fooled into
> thinking that the IC was bad simply because the act of taking the old 
> IC out
> of the socket and putting in the new one created enough scraping 
> action to
> clean the oxide off the socket and fix the real problem.  What he 
> doesn't realize
> is that the next time the synth gets moved, or played, or goes through 
> some
> kind of temperature change, that new IC may move again in the socket, 
> just ever
> so slightly, but enough to make the problem come back.  Murphy 
> cheerfully
> reminds us that this is most likely to happen onstage at your next 
> very important
> gig, probably right in the middle of your big showstopping synth solo, 
> once
> again redefining the word "showstopping".
> Michael Bacich

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