Signal Strength Question?

Started by modsquad, September 04, 2007, 12:48:32 PM

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modsquad

I posted a couple of days ago about my Ross Phaser project.   I finally got output after maginfying glass and checking all contacts and traces.  The only problem now seems to be that the output is barely audible unless I crank the amp way up.   Then you can barely hear it.   I am looking for some advice on where to look for bad component, etc. in the cirucuit.   I am using the Tonepad layout and schematic.   I do notic that if I poke around the 100pf cap that I get more volume out of it..
"Chuck Norris sleeps with a night light, not because he is afraid of the dark but because the dark is afraid of him"

Mark Hammer

Assuming that you are making some sort of connection only at the point where you believe you are pressing, that would suggest a problem with the signal continuity at the input.  If I were you (how come this isn't an "IIWY" contraction yet? ??? ), I'd make a point of verifying that there is continuity from the to-effect lug of your switch to the junction of the 100pf/.01uf/and 1k components.  This could be a result of a cold solder joint or a crack in the PCB.

modsquad

Okay checked and as far as stupid me can tell, there is continuity.    Rechecked the solder joints and PCB.   They are fine.  But if there was a problem wouldn't there be no signal.   Would a bad capacitor i.e 100pf cause a signal strength issue going into the OP-AMP?
"Chuck Norris sleeps with a night light, not because he is afraid of the dark but because the dark is afraid of him"

petemoore

Okay checked and as far as stupid me can tell, there is continuity.
  the problem I had to have now is that I'd put circuits on box sides, they'd work with circuit they were crammed in with, but then when something goes wrong, I can't get access good enough to trace it, probe it, push it around, test voltages/resistances in enough places for the problem to surface it's ugly head.
     Rechecked the solder joints and PCB.   They are fine.
  define 'fine'.
    But if there was a problem wouldn't there be no signal.
  that would generally be a problem,
  A problem is an obstacle which makes it difficult to achieve a desired goal, objective or purpose. It refers to a situation, condition, or issue that is yet unresolved. In a broad sense, a problem exists when an individual becomes aware of a significant difference between what actually is and what is desired. Every problem asks for an answer or solution.
 
Would a bad capacitor i.e 100pf cause a signal strength issue going into the OP-AMP?
  I thumbuzz test but an audio probe would probably that the 100pf [non-polar] capacitor used for who knows what [probably not in the signal path] isn't the cause of the disfunction.
  It may sound simply complicated, but it's a matter of making everything represent the schematic on the board.
  You can divide and conquer.
  Read the Debugging thread, taking voltages and audio probing often quickly limits problem searching down to a circuit fragment.
Convention creates following, following creates convention.