[sdiy] Re:Need Some Advice

[harry]

Amen Brother...

Amp Diplomate sockets... the twin leaf ones. I use them for EVERY IC..
and have NEVER had a socket failure either personally or professionally
(and professionally my clients are BIG THREE automakers and their plants
are very nasty dirty places... almost as bad as most nightclubs...)

Remember... divide and conquer (maybe thats not what Grant said but its what he
meant...).   Large circuits are made of small functional blocks.

The hardest blocks to troubleshoot are often VCO and VCF (esp the state variable)
because of all the circuits they rely on a feedback loop to operate at all.  Most
other circuits have a "goesinta" and a "goesouta"... just follow the signal.

WITH YOUR SCOPE.... (but that is another rant !!!)

H^) harry

PS... ask for assistance on list (or off). We'll help. We'll need to see a
schematic and
know what test gear you have / use.  It will take time but you will eventually
succeed.

Grant Richter wrote:

> Every single item on David's list is spot on!
>
> It is specially important to use sockets everywhere you can. Use the Amp
> twin leaf sockets. Single leaf sockets are not very reliable. A 16 pin twin
> leaf socket should be about a dime. Sockets without chips in them are a
> whole bunch of test points that are easy to get at.
>
> Do not put the chips in the first time under power!
>
> Use an ohm meter to make certain that all the ground connections are
> actually connected to ground.
>
> Power up the board and use a meter to make certain the all power pins of
> each chip socket are showing the correct voltages.
>
> Make sure you turn the power off whenever inserting or removing a chip from
> a socket.
>
> Start with one simple section, put only the chip in for that section and get
> it working first. Then add one more chip and test again, if adding the chip
> makes the previous section quit working, then troubleshoot the new section
> until they both work. Then add another chip and test again. Continue using
> this method until the whole assembly works.
>
> It is extremely difficult (if not impossible) to troubleshoot a board with
> all the components in place! There are so many possible interactions that
> you must reduce the number of possible error sources to something
> manageable.
>
> For instance, with a VCO, get the current source working first using a
> multimeter to monitor the current. The add the chips for the oscillator core
> and get it oscillating. Then add each waveshaper chip individually and
> troubleshoot them in order from simplest to most complex.
>
> > Most problems are the result of (not in any particular order):
> > 1.  Wiring errors (always double check before you first switch on).
> > 2.  PCB errors (broken tracks, bridged tracks, errors in the track layout
> > (less likely) ).
> > 3.  Components having the wrong orientation, i.e. diodes, transistors, ICs
> > and polarised capacitors inserted the wrong way round.
> > 4.  Dry joints (solder joints that look OK but don't actually make an
> > electrical connection).
> > 5.  Solder bridges (where you've inadvertently joined two things with a blob
> > of solder that shouldn't be joined).
> >
> > To help avoid such problems you should:
> > 1.  Check the PCB for cracks and errors.
> > 2.  Check the PCB for solder bridges.
> > 3.  Always double check all wiring before you first switch on.
> > 4.  Always double check component orientations before you first switch on.
> > 5.  Ensure solder joints are bright and shiny (a dull joint is sometimes a
> > dry one).
> > 6.  Use sockets for ICs and the more expensive transistors.  This will
> > greatly aid fault diagnoses and avoid the possibility of overheating
> > components when soldering.
> > 7.  Handle ESDs (electro-static sensitive devices) correctly.