intermitent on off

[WorkBench]

I am resurecting an old tube screamer and seem to have it all set.  the only problem is that the on off is intermitent.  I hit the switch and it works 3 out of 5 times.  It will come on then it wont come on!  Does anybody have any ideas as to waht could be causing this? Thanks!
Chris

[AL]

Sounds like a bad switch.  Small Bear has replacements for TS-9's but he won't be open for a few weeks.

http://www.smallbearelec.com/

AL

[WorkBench]

I have changed out the switch and the problem still persists.  It must be something else, any furhter thoughts?  Thanks!
Chris

[David]

Okay, my guess is one of the wires connected to the switch is intermittent at some point along its length.  Movement and vibration induced by stepping on the switch is enough to "make" or "break" this intermittent point.  I had this with a Fuzz Face clone I built a couple of years ago.  I made the mistake of using solid wire to make my outboard connections to the circuit board.  At least one became intermittent.  Got that pedal to work exactly once and wound up recycling it because I got so frustrated.

[AL]

Is the switch making a "click" noise when it's engaged? There is a spring connecting the part of the pedal you step on to the actual switch. I have seen numerous "broken" TS-9's that the spring had come loose or had fallen off.

Also, are you stepping on the pedal in the same place every time? Sometimes, if the switch is not in the "exact" spot, you have to hit the pedal on the bottom - if you get near the top (closer to the knobs) it won't engage.

And check out David's comments - loose wires/cold solder joints are always a potential problem.

AL

[WorkBench]

I am using a carling MXR type switch outside the box right now.  I lost the spring to the original switch.  I will try to rewire the switch tonight with new wire.  Thanks alot!
Chris

[AL]

There is a little bit of extra circuitry that goes along with the original switch. Just replacing the original switch with a mechanical (carling) switch won't work. You've got to remove the excess circuitry. I've never done this myself but there are those here that have. Ask around and I'm sure someone can tell you exactly what to remove (or not remove).

AL

[WorkBench]

Well, I have rewired the thing, checked all solder joints, and it is still intermitent as far as switching it on and off!  I can not find the problem!  Could it be a transistor or the IC?  Anybody know how and where the switch circuit is in these things?  Thanks!
Chris