Noob questions...I need your help, please

[6stringer]

Perhaps you can help me with at least one of these issues......  Thank you in advance

Question 1: I've just built an "Easy Face", using the Cara Facil layout and a Ge transistor from Small Bear.   I set the trim pot for 4.5v and it sounds good.  The tone control does not seem to have much effect at all,  I've checked the whole circuit for shorts and verified the component values.   Is there something I can do to get more variance in the tone circuit?

Question 2:  I've also just built a JD Sleep's Rodent (Rat) pedal.  Using his PCB and
Component values I got from General Guitar Gadgets.   It sounds good too, but....

1.   The LED still glows slightly with the circuit switched off, I know I can change a resistor to fix this, but which one and to what value?

2.   The "Filter" pot has almost no effect.  What's up with that?

3.   The "Drive" pot has very little effect at all except it turns the pedal off  when
turned all the way up (clockwise).    Is that correct?

Question 3:   Is there a good tutorial on how to best use the 3PDT switch pin outs in a layout that
                     calls for a  DPDT switch?

Is this the correct forum to post these questions?
Thanks for your help!

[aron]

Question 1: I've just built an "Easy Face", using the Cara Facil layout and a Ge transistor from Small Bear.   I set the trim pot for 4.5v and it sounds good.  The tone control does not seem to have much effect at all, 

Can you link the schematic? We need to see what tone control you are talking about.




>1.   The LED still glows slightly with the circuit switched off, I know I can change a resistor to fix this, but which one and to what value?

There should be a resistor in series with the LED. This is the one that you alter (make bigger in value).

>2.   The "Filter" pot has almost no effect.  What's up with that?

Maybe you have it wired incorrectly? See below

>3.   The "Drive" pot has very little effect at all except it turns the pedal off  when
turned all the way up (clockwise).    Is that correct?

See here:

The drive pot, tone pot, filter pot all have something in common - they use pots! There must be something you are doing that is wrong when you wire these up. That's my initial guess.

>Question 3:   Is there a good tutorial on how to best use the 3PDT switch pin outs in a layout that
                     calls for a  DPDT switch?

A 3PDT is exactly the same as a DPDT except it has one more set of lugs. Just ignore the extra set.

http://www.diystompboxes.com/beginner/123DT.jpg

[Mark Hammer]

Depending on how much high end finds its way to the filter section, and what cap value you are using for the filter control, it is quite possible that the filter control is doing a very nice job of removing treble that doesn't exist.  For instance if the 100pf feedback cap (C3) and the 30pf compensation cap (C4) were on the highish side of their respective tolerance limits, and the 3n3 filter cap (C8) was a little on the low side, that could easily result in a tone/filter control which is set higher than the effective bandwidth created by the caps in the clipping/gain stage.

Try a 4n7 (4700pf, .0047uf) cap instead and tell us if it makes a difference.

I second Aron's recommendation to follow up on your pots as a source of potential trouble.  At the very least, check your wiring, and give the rivets that hold the solder lugs to the pot a little pinch with your needle nose pliers - just because the wire is soldered to the right place doesn't mean the solder lug is making good contact with the resistive element inside!

[6stringer]

Thank you for responses.   The switch info is most helpful.   Here are the links to the schematics:
http://www.tonepad.com/getFileInfo.asp?id=36               for the Easyface
www.generalguitargadgets.com/diagrams/rodentsc.gif     for the Rodent (Rat)

On the Rodent circuit:  I determined that R13 (22k) is the resistor that limits the LED voltage,  I tried 47k and 1 ohm resistors, the LCD still glows slightly.  I tried a 100 ohm resistor, it fixes the problem, but also turns the LED down too much when the circuit is active,  I will try some values between 1 and 100 and see what works best.  Am I doing this right?

I rechecked the wiring on the pots (twice) and it seems correct,  also check the pots with a meter to be sure that they were operating  correctly,
all worked fine 0-100K (approx).   BTW, the volume pots on both circuits seem to be operating correctly. 
I will try the 4n7 cap and let you know what happens.

Thanks again for your help.

[PenPen]

I think what they mean, at least from your description of the Gain pot on the Rat, is that you have it wired backwards. It happens to everyone. The way to verify you have it right is to measure the resistance between the middle lug and the left lug going to back to the chip. Look at the pot with the shaft facing up, the round part pointing away. The left lug should be wired to feedback loop input, and the middle lug is connected to the right lug. Measure the resistance from the middle lug to the left lug with the pot turned all the way up clockwise. It should be at max resistance at that setting. Counter clockwise lowers the resistance.

[6stringer]

OK, On the Rat circuit, I changed the .0033uf cap to .0047 and now have a much more usable range of tone control with the "Filter" pot.
Following PenPen's suggestion, I switched out the leads to the "Drive: (gain) pot and now that works correctly too,  still not much control over
the amount of distortion, but the quality (fatness) of the distortion is effected with that pot.    It would be great to be able to adjust the amount
of distortion that the pedal puts out.   The volume control works correctly.
I tested a whole range of resistors with the LED and found that 8.2k works perfectly.
Thanks for all of your help, it is most appreciated and has really improved this project.   
Thanks for your time and willingness to trouble shoot these issues.

[PenPen]

No problem man. I shouldn't be posted after getting home from the bars, but it sounds like something is screwed up with the values in the feeback loop there. I have an original Rat, and believe me, the gain pot does a LOT of changes to the distortion. I'll have a look tomorrow when I'm sober.