P19 Sustain Pot Problem

[squirrels]

I built up a P19 and the sustain pot is acting funny. It cuts out at both extremes of the sweep. I probed the circuit and got signal all the way through and the voltages are:

Q1&3
C- 4.2v
B- 0.6v
E- 0v

Q2
C- 5.5v
B- 0.65v
E- 0.1v

Q4 (Off the top of my head, didn't write it down)
C- 4.6v
B- 1.3v
E- 0.6v

Pics:





Layout: http://tagboardeffects.blogspot.com/2012/05/skreddy-p19.html?m=1


NOTES: transistors are BC550C and are soldered into the sockets. One or two 10k are 9.1k and I subbed one or two 200r as well. The solder looks like it had cold joints, but it's not very good solder. Also there was an extra cut I accidentally made on the top leg of the 18k. I corrected it with the leg.

Any thoughts what the problem could be?

[squirrels]

I'm gonna bump this one before I rebuild it.

[Ciaran Haslett]

Did you try simply changing the pot?  

My The Depths build was acting up during testing.  The LFO wouldn't kick in.  Probed/tested, swapped Q's for about an hour.  Nothing...so for no reason whatsoever I decided to reflow every joint (even though they all checked out under continuity test) and reflowed the Rate pot.  LFO kicked in.  But died about 1 minute later!

Turned out the heat of soldering was expanding the contacts in the pot and making a good connection...but as it cooled this contact was lost.  Swapped the pot for a new one and no problems since.

[squirrels]

Thanks for the reply Ciaran. I tried that out with no change. This happened once before on a different Muff build and I never got it sorted out.

[Travis]

I see multiple potential solder bridges

[Ciaran Haslett]

Sustain 2 1 row too low?

[squirrels]

I'm at work right now so I can't check anything.

Travis, any areas in particular?

Ciaran, maybe. I haven't looked at it since I made the first post. It may just be the insulation of the wire.

[squirrels]

Definitely the wire from sustain 2. Sounded very weak. No distortion at all, just a clean boost. Swapped the BC550Cs for BC239Cs with the same result. It may not be what I'm looking for anyway.

[Marbles]

That's weitd. I have built it twice and thought it sounded great! Can't remember what I used though.. One was sold and the other a birthday gift.
But knowing myself playing safe, I def should have use the BC5550C's

[squirrels]

I built an Iron Bell awhile back and really liked that so I think there may be other issues with it. Can't believe it was a misplaced wire. I can't remember the last time I did that.