4ms phaser problem... not phasing...

[marrstians]

i've been trying to build the 4ms phaser and i'm having a little touble... it doesn't phase at all... i've been trying to use an audio probe on the circuit but i'm not sure how the blend pot affects the process... i get signal from all of the outputs of my ic's untill i come to the last output of the phase section... pin 1 of ic 2... i have good signal going into the inputs of that section but almost no output... i've traded out ic's to make sure it wasn't a ic problem but it still did the same thing... all my voltages are right and all the soldering looks good and caps are in there respective polarity positions... i'm not sure what the next step to take is...







http://commonsound.com/phaseur.html

[mattv]

So you have input, but little output from an opamp? Quadruple check the component values and connections involved in that stage.

[marrstians]

the componets are right... i get signal all the way from input to output with the blend pot turned down... just a stright dry signal... when i turn the blend pot up to get a wet signal it turns the volume down with very little output and no phasing... it's almost like the blend pot grounds out the signal but it's not grounded...

[Paul Perry (Frostwave)]

Looks like that suspect amp stage just isn't amplifying, for some reason. That would make the pot behave as you say. An IC op amp stage will fail to amplify if the bias is bad, or the resistors are wrong. Not much else will stop it, if the power rails are right!

[toneman]

did U use a pcb?
if U perfboarded the Phaser, re-re-re-check the wiring.
use ohmmeter 2 check +9v, gnd, and bias paths.
make sure LFO is FLOing.
then make sure it's actually driving the LEDs.
last, make sure photores's R changing Res with the LFO/LEDs.
a scope would make troubleshooting a lot easier.
tone

[marrstians]

yeah... i used a pcb... all of the other trouble shooting i've done and it's checked out... all the lights blink and react to the speed controls and stuff... if the ic is mis biased wouldn't all the stages be crappy? the left other side of the ic is working fine just not the last phasing stage... hmmm...

[mikeb]

Even if the soldering looks good, it's worth taking the time to reflow the joints around that area. Then, check for continuity between all parts of the circuit in that area also, and I'd suggest measuring resistance to ensure it matches what values you think you put in and matches what it says on the schematic. I've found sometimes it's better to do things the 'dumb' way as then it eliminates a lot of possible sources of error.

Mike