Tonepad Rat Filter control has no effect

[Deano]

Hi,

I have completed my first build - a Rat clone from tonepad.com.  The pedal works ok but the filter doesn't appear to do anything.  The pedal also seems quite 'trebly' to me.
Could you help me find the problem, it's driving me insane!  I have posted the measurements below.  I have checked for cold solder joints and re-heated all joints several times.  I have also changed the 1k5 resistor, and the 3n3 cap.  I swapped the pot for the one on the drive control to see if the pot was faulty but it was still the same.

1.What does it do, not do, and sound like?

The pedal works ok in both bypass and with the circuit engaged.  The filter control appears to have no noticable effect on the sound.

2.Name of the circuit

La Rata, PCB ordered from tonepad.com

3.Source of the circuit (URL of schematic or project) =

http://tonepad.com/getFile.asp?id=89

4.Any modifications to the circuit? Y or N

No

5.Any parts substitutions? If yes, list them.

Yes: the 30pF capacitor is replaced by a 33pF.

6.Positive ground to negative ground conversion? Y or N

N

7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery
terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => 8.33v
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack
to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to
signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does
not have a plug in it. With the negative lead on signal ground, measure the following:

Voltage at the circuit board end of the red battery lead = 8.31v

Voltage at the circuit board end of the black battery lead = 0v

IC1 -> LM308:
P1: 7.56v
P2: 4.12v
P3: 1.97v
P4: 0v
P5: 0v
P6: 4.12v
P7: 8.28v
P8: 4.19v

Q2 -> 2N5458:
C(D) = 8.27
B(S) = 1.66
E(G) = 0

D1 -> 1N914:
K = 0
A = -0.00

D2 -> 1N914:
K = -0.00
A = 0

D3 -> 1N4002
A = 0.00
K = 8.26

Here is a photo of the board.  Ignore the fact that the 1n4002 and 1n914 are the wrong way round, and the horrible red wire.  I swapped the diodes and re-wired after I took the photo.

[bipedal]

I don't see any obvious glitches from the pic you provided. (By the way, the picture seems to show the 1n4002 and 1n914 diodes already in correct orientation, per tonepad's layout...)

One note that may or may not be related to the problem you're experiencing...  There's no need for three wires to be run from the board to the Filter pot.  Instead, short lugs 2 & 3 at the pot with a short bit of wire (I use spare leads snipped from resistors), and you can remove either the lug 2-to-board or lug 3-to-board wire.  Will save a bit of wire and result in a "cleaner" build.

My best guess -- a solder bridge somewhere.  Could you post a close-up pic of the trace side of the board?

[slideman82]

I agree with that, filter pot only needs 2 wires, you have to bridge  lugs 2 & 3 to make pot works clockwise (from bass to treble), and you use only lugs 1 & 2. Also, some friend told me it's very trebly, so, the major mistake in this stompbox is that 100p cap, it has to be at least 220p, try this, probably will sound better. That's my tip!

[reverbie]

Wire #1 from Filter looks like it has a little hair sticking out and shorting against wire #3 of the level pot....look closely at your component side where the wires meet the circuit board.

[Deano]

Wire #1 from Filter looks like it has a little hair sticking out and shorting against wire #3 of the level pot....look closely at your component side where the wires meet the circuit board.

You can ignore the wiring in this photo as I re-did it all.  I used wire that was too thick and it was pretty messy.  I will try to take some more photos and post them.  In the meantime I will try and short lugs 2 & 3 with a cut off resistor lead and see if that makes any difference.  I'll also try and post some photos of the trace side of the board.

[frokost]

Lug 2 and 3 are already connected on the board, so bridging on the pot won't make any difference. My guess is that there is a short between lug 1 and 2 or 3 in some way, either on the pot or on the board. A picture would be useful.

[slideman82]

Did you try replacing the pot?