At wits end with Ross Phaser...

[modsquad]

I have tried everything, resoldering swapping ICs out, etc.  All the voltages are fine but the LFO is not "phasing" the signal.  All I get is a modest overdrive sound and no phasing.  The voltages in the LFO IC are jumping around like they should but there is no effect on the sound.

Stan

[Mark Hammer]

Trouble is that there are a LOT of IC pins that have to be making appropriate contact in order for the entire wet/phase-shift path to make its way through to the point where wet and dry mix.  If you have used sockets for those two LM13600 chips, then there are 32 pins altogether that need to be in proper contact.  If you have used sockets for your chips, either consider unsoldering the sockets and soldering the chips directly to the board, or try reseating the chips in the sockets.  Though it doesn't happen all THAT often, it happens often enough that a pin gets bent under the chip during socket insertion and fails to make contact with the socket for that reason.  Unfortunately, what is generally a convenience with Francisco's board layouts (their compactness) can be a bit of a hindrance to being able to see such construction errors.

I'm not guaranteeing than any of the above is the source of the problem or the solution, but they are most certainly build problems that happen often enough to a great many of us, and should at least be checked off the list of possible causes before moving to more time-consuming or invasive solutions.

[modsquad]

Wouldn't the voltage for those pins be off if that was the case?  The voltages are the same as the ones for another one I built.

[Mark Hammer]

Some yes, some no.

That's the nasty aspect of this particular source of nonfunctionality.  You get pin voltages that read what they should and others that have no particular "necessary" voltage that ought to be there, so you ignore them and think the board "reads good".  Keep in mind, that the brunt of those pins are all connected internally so they could still show one of those arbitrary voltages without actually being in contact with anything else on the board.  Also remember that a micron may be incredibly small to us, but to an electron its like jumping the Grand Canyon on in-line skates.  It can easily happen that a pin makes sufficient contact when we apply the pressure of our meter probes for measurement purposes, and then springs back the few thousandths of an inch out of contact after we pull our probe tip away.  Again, this may not have happened in your case, but trust me, it happens.

[puretube]

always measure @ the actual IC-pins!
not at the respective (PCB) copper-pads...

[StephenGiles]

So true, many's the time I've had a board not working and all that was wrong was one pin of an IC was not soldered, which is easy to do in bad light.