Intermittent Cut- Off when effect is engaged

[tonenob]

I had built a TS-808 clone a month ago. After a few debugs, I managed to get it working and sounding good. 1 month later, problems start to surface. When the pedal is engaged, it worked fine, but only for a certain period, then the whole effect is cut off. Strangely, if you leave it on, it will come back to you sooner or later. Its very random, sometimes it takes about 2 mins to cut off, somtimes 1 or so.

The tubescreamer clone was my first build and I rushed the job abit, so some soldering joints might be lousy. Having that in mind, I dismantled everything 2 days back, desoldered all wiring joints and redid them again. This time, I'm quite confident that the soldered joints are strong.

But the problem remains, even worse in fact. Now the pedal might take 1 minute to hear any effect and it cuts off a minute later. Its just a slight pop, and everything is gone, no effect whatsoever. The LED is shining bright and the effect is good in bypass mode.

I do not have any idea whats wrong with it. Its very frustrating though. Will I damage my pots, jacks and 3PDT switch if I desolder them and redo them again?

Any help would be great !

[tonenob]

erm..... anyone...?

[Mark Hammer]

What you describe sounds more like a continuity/discontinuity issue than an electronic issue such as the discharge rate of something or heat buildup, simply because the signal quality seems unaffected, merely whether you HAVE signal or not.  This would, in my experience, point to an issue in one of the many areas where there is a contact that relies purely on pressure.

Just out of curiosity, is the chip socketed?  If so, try the following.  Scrape the pins of the IC with a sharp blade so that they are nice and shiny, and lightly tin them to increase their perimeter.  Then reinsert the chip and see if the problem goes away.

Another area where continuity issues can crop up is pots.  I find sometimes the rivets that hold the lugs need just a little pinch to make them more secure and provide more consistent contact with the resistive strip.

Finally, some have complained about failing stompswitches in past.  The rates of switch failure noted are way in excess of what any manufacturer might tolerate if they wanted to stay in business with corporate clients, so I figure that it must be an error type induced by the builder, and especially the novice builder.  If you pry the tabs on the side of the switch to pop it open (don't lose the pieces!), you will see several little see-saw pieces inside that we will call "rocker contacts".  When the switch is assembled, a small amount of grease is dabbed inside the switch chassis to temporarily hold the otherwise free-resting rocker contact in place.  The grease is not essential to the functioning of the switch, merely to its speedy (hence low-cost) production.  Sometimes, when novices are building pedals and wiring up switches, they can tale too long to solder leads to the switch.  While the heat buildup may not appear to physically damage the switch, it ends up being enough to cause the grease to liquify, and flow along the rocker contacts, coating them with what is effectively an insulating material that prevents making contact.  Since this IS grease that remains viscous at room temperature, and not solder that hardens, you can expect its impairment of the switch contacts to be somewhat unpredictable and to come and go.  I think many of us have had stompswitches that provoked the question "Why the deuce won't it work now!!", and while I can't prove it, my sense is that it results from just such unintended internal goopiness.  The good news is that if you can successfully open and reassemble the switch, you can simply clean the rocker contact off with a paper towel and reseat it, "rehabilitating" the switch.

As an aside, my first computer mouse (a traditional ball-based unit), many years ago eventually became unpredictable in its functioning.  Opening it up I saw these "felt pads" to the side, not realizing these were NOT part of the mouse but were accumulated compressed dust that was the real source of the problem.  Opening up a stompswitch for the first time (because I thought, "this switch is a write-off") I noticed the "protective coating" on the rocker contact.  Took me a little while to realize that the protective layer was actually the very source of the malfunction and NOT something the stompswitch manufacturer had done to assure contact longevity  .

[R.G.]

It's possible that there is a reverse biased electro cap in there with only a low reverse voltage across it. It may have become damaged slowly by the persistent low reverse voltage.

That might fit the symptoms you're describing.

[aron]

Interesting. I had a project like that. I never figured it out. I wonder if I had the same electrolytic problem.