Does this sound like a faulty trimpot?

[msb69]

I successfully replaced the SPDT switch in my script logo Phase 90 with a Carling DPDT switch for true bypass.  While the unit was opened up, I experimented with the internal trimmer to see what it did throughout its range.  Before turning it, I carefully marked where it was set -- so I could return it to that setting.

I played around and found that the unit was not doing any phasing at all unless the trimmer was set at where it originally was by the factory.  As such, I set the trimmer to my mark and closed up the pedal.  But when I turned the pedal on, I had no phase effect.  Through troubleshooting I discovered that the trimmer is acting a little crazy.  For example, the phase effect will stop if I touch the top of the trimmer with my micro-screwdriver, or if I press down lightly on the trimmer with my finger.  Thus, it seems clear that when I close up the unit, the foam is pressing up against the trimmer and causing it to go whacko.

Any ideas what could be wrong?

[PerroGrande]

Check the soldering around the trimpot.  Could be a cold joint that is making/breaking connection when flexed.  Failing that, it certainly could be a bad (or dirty) trimmer.

[Papa_lazerous]

you may have damaged the trimmer.....

[petemoore]

Any ideas what could be wrong?
  Could be a dead spot in the trimmer, first find out if the pot is good/bad/inbetween.
  Try using the DMM on it [if you can get a clip or two on a conductor actual potlug somewhere...the leg or where it connects], turn the trimpot slowly and you should see steady rise in R value, this checks the trimpot for 'holes': when the resistance drops to 0, caused by the wiper not conducting, it's probably wafer damage.
  "repair' might be good enough as putting the unwanted wafer 'hole' where it doesn't matter, most of the potrange is wasted in 'nophase' zone [only a small portion of travel produces phase sweep], moving the wiper to another spot can restore pot and phaser function..depends, in most circuits a dead spot in a pot is a real drag, but if you can get away with just trimming value enough to move the wiper to just 'beside' the dead spot, and have sweep enough to adjust out of phasing sweep on both sides without hitting the hole, tacking a carefully bent/tinned resistor across a couple tinned top of board lugs [or wire connected to lug] might just do the trick.   
  My opinion is wafer/wiper non-conducivity development may be catalyzed by the wiper and wafer reacting to each other over time, or perhaps the shapes attract dust, which attracts moisture etc., whatever it is sometimes all you have to do is so slightly adjust or even touch make wiper connect again, massaging with tuner cleaner...maybe, trimpots are easily caused to be 'mechanically challenged'.
  Having ever so slightly adjusted just off where a factory setting has stood for 'ages, restored wiper to wafer conduction has ='d 'repair'...but it's got to be in a circuit where having the hole in wafer 'over there' doesn't matter.
  I think I've only tried cleaning a trimpot once, I know that even light  'sidetorque' on the wiper screw can cause misalignment, I got a screwdriver stuck and have damaged trimpots other ways, I now use a too small flat-tip driver in the crosstip trimpots to adjust them.
  Say the pot is 250k, maybe trying a 1meg or so on it, somehow paralleled [testclip-wires again], in different ways would find the phase sweep available with the wiper hitting no holes.
  Series resistor would be a bit harder to install, replacing pot would be better for sure in that case.
  Might not work, depends...nice if it does, prevents the need to yank the board, yank the trimpot...re-install, re-assemble and hope all that went well, ..on the 'fast' heat [pre-tin everything, cool, solder in place] prevents bottom of board solder flow.

[ayayay!]

I can tell you those trimpots have a very narrow range of useability on that pedal.  I'm sure it's a matter of cost, using not necessarily the right pot for the application, but the cheapest one.

But still, yes if the screwdriver touching it gives you your effect back, I'd suspect the pot is faulty. 

[Paul Perry (Frostwave)]

Is that trimmer one of those 'open' style ones? If so, they are notorious. they aren't really intended to be tweaked more than a couple of times.
Replacing it with a more robust enclosed one would be a good thing, or even a multiturn.

[gez]

Replacing it with a more robust enclosed one would be a good thing, or even a multiturn.

+1 on the multiturn.  Although a pain to adjust, they're less likely to be knocked out of kilter once they're set (and even if that happens, the outcome isn't disastrous).