Tube Screamer Help

[Leevibe]

Right on bro! Feels good, no?

[tunatuk]

Feels better, that's for sure. Just need to figure out the tone pot. It should have an audible change with the sound, right?

[chromesphere]

Good one tuna!  Well the Tone pot will have a very obvious effect when its working so theres probably, you guessed it, a short or component value error Make sure there are no shorts between the wires of the tone pot as well

[Leevibe]

Feels better, that's for sure. Just need to figure out the tone pot. It should have an audible change with the sound, right?

Yeah, it should work but you're past the worst of it. I would start by tracing your tone pot wires. Make sure they're the right way around. If the pot shaft is facing down/away from you, the lug order is 3,2,1. Make sure none of your wires extend through the lugs and contact the pot body too. It should be a w20k pot it think. I haven't built a TS for a while.

[chromesphere]

Tone will work even if it is wired the wrong way around (backwards, 123 -> 321) but still take note what Lee says because you will need to learn how to wire them up (if you want your pot dial turns to be the right way around).  The wrong pot value could be a problem though.  Either that or its a short / component value error / etc etc

[tunatuk]

The tone pot is wired up correctly, and I cut the wires, and resoldered them on.  I was unable to find any short in it.  I double checked tonepad's website, and it is a B20k pot, which is what I have wired up.

[chromesphere]

ok, there are other components in the tone control section of the circuit that make the tone pot work the way that it should.  So you must have a wrong value, solder bridge, etc somewhere else. 

[ynot333]

Is the resistor for the led on the neg term  looks like your shorting it that way  from puc looks like its touching metal box 

[tunatuk]

I'm trying to trace backwards from the tone pot...

http://www.tonepad.com/getFile.asp?id=81

I see several traces coming from the tone pot, and since I don't know exactly which ones are in the path, I checked them all.  The entire board is correct with values.  I use a ring light with a 5x magnifier on it to examine boards and solders, and I don't see any bridges.  I'm still using my rig tester to troubleshoot, so I don't know where it could be shorting out.

I know the odds are low, but I'm going to try a new pot, just to ensure that it isn't faulty.

[jkokura]

I should do a tutorial on using an audio probe to find faults...

But in the meantime, the best thing to do is to take a copy of the schematic, and then trace through the circuit with a highlighter or pen or something. Start at the input, and then follow the path. Everytime a part diverges with the main circuit, follow it and it will usually lead to either Power or Ground. You should get no sound at either spot.

Return back to the main circuit where you left off each time, and keep tracing forward with the audio probe. Sooner or later you will hear or find where something goes wrong. The trick is learning to recognize something that isn't right.

In this case, you feel that your tone pot isn't working correctly, so in that case you could in theory jump straight to that section of the schematic, which might really help you narrow in on the issue.

Jacob

[Gledison]

I should do a tutorial on using an audio probe to find faults...

But in the meantime, the best thing to do is to take a copy of the schematic, and then trace through the circuit with a highlighter or pen or something. Start at the input, and then follow the path. Everytime a part diverges with the main circuit, follow it and it will usually lead to either Power or Ground. You should get no sound at either spot.

Return back to the main circuit where you left off each time, and keep tracing forward with the audio probe. Sooner or later you will hear or find where something goes wrong. The trick is learning to recognize something that isn't right.

In this case, you feel that your tone pot isn't working correctly, so in that case you could in theory jump straight to that section of the schematic, which might really help you narrow in on the issue.

Jacob

Jacob, a tutorial would be pretty much appreciated!

[Stomptown]

The Tonepad doc does say B20K for the tone pot but the correct pot is actually a W20K pot. The taper of this pot will make the tone function better if nothing is actually wrong. IIRC I build a tonepad tubescreamer and the tone pot was not very useful with a B20K. In fact, I've had this problem with all tube screamers that I've build using a B20K. My suggestion is to order a W20K next time you place and order and switch it out. You can get the solder lug style at small bear or Mammoth and tayda carries a straight PCB pin style that could be used in a pinch. If you have a B10K you could give that a try as well. I know that BYOC uses a B10K for their tube screamer clone and it definitely works better than a B20K...

[Leevibe]

Last time I ordered pots from SB they had w20k in 16mm pcb pin

[Stomptown]

Last time I ordered pots from SB they had w20k in 16mm pcb pin

yeah right angle pcb pin should be available at SB but the tonepad pcb doesn't use pcb mount pots. The tayda pcb mount are not right angle so those would work better and obviously the solder lug would be best...

[chromesphere]

Tunatuk mentioned the tone pot doing practically nothing at all.  My Tonepad tubescreamer tone pot is bunched up one end, but it definitely makes a big difference from 0 to 9.