Tone control inop

[NuckChorris]

I just built another ecstasy OD and the tone control does nothing. I've built one before with no issue using ver1 layout. I used ver2 this time and everything works but the tone knob. Tried a new pot but still nothing. Where it calls for a 1u cap I used a tantalum. Would this matter? Can find any tracks touching or anything. Any ideas??

[NuckChorris]

The pedal isn't bypassing correctly either. The volume still works when it's off. Oddly I can hear the tone working then too. Must be something I've done offboard

[NuckChorris]

I fixed the bypassing issue. But for the life of me can't figure out why the tone control does nothing.

[rocket88]

Tantalum caps are usually polarized, if I remember correctly. So if the layout calls for a no polarized 1uF cap and you use a polarized one if it's not placed correctly it won't work and can explode.

[NuckChorris]

I put the cathode/negative to the top of the layout with the cathode going to the row that links to the IC. It hasn't exploded or anything like that. Everything works except the tone control. It has worked randomly once or twice but nothing now. Tested the pot. Seems ok. Put two others on just in case. Still nothing. No clue what it is. Frustrating.

[Beaker]

If it did work, but does not work now, it suggests a short or dry joint somewhere.

[NuckChorris]

Could it be anything offboard? Or is it pretty much a problem on the board?

[motterpaul]

I don't know about you, but I often make mistakes with pot wiring, getting the ground right, etc. Double check the pots wiring. I still have to mark the 1 & 3 lugs, because if I turn a pot around I still get confused.

Also, when you have a tone stack, it is not unusual for the three pots (Bass, Mids, Treble) to be very interactive to the point where if the mids are off you won't hear the treble working (for example) - try different settings on the tone pots to see if you have more control than you think.

Also - the bass is reverse log, which means that if you did not use that exact part, and you used a regular log, the taper is completely backwards, and you would not hear it working unless it was full off (CCW) - you would be better off with a linear pot than an unreversed log. Then you could reverse the leads to make sure it boosts when turned clockwise.

[rocket88]

i agree with what beaker said to do. but i checked the layout, and that 1uF cap is shown as a non-polar. i've had issues with tantalums before, and typically avoid them like the plague, but i would remove the 1uF tantalum you have in there now and replace it with a poly or electrolyic and see what happens. that 1uF is connected to tone 3 so that could be the issue.

[NuckChorris]

Ok I'll try that. I think all I have here in 1uf is tantalum though. :(

[Ciaran Haslett]

Try putting 2 470n or higher non polarised caps in parallel (effectively adds capacitance together).  That'll get you close to 1uf and will at least confirm if this is your problem area

[NuckChorris]

Put two caps in place of the tantalum. Still nothing. Really scratching my head now

[Ciaran Haslett]

Then that was never your problem!  At this stage...I'm thinking audio probe (best debugging tool going) or hi res pics of the front, back and wiring.

[rocket88]

2nd. Something is really a miss then. It could be a bad IC, missed solder joint, another defective part, the best thing to so is take and use an audioprobe to see where you're losing signal/signal be messed up from what if should.