Help troubleshooting DIY Tonebender MKII

[Electric Warrior]

Maybe you're not getting a signal because it's gating. Have you tried swapping around the transistors?

[John Nada]

My 2 cents says R6 is not really connected at both ends.

I just measured it the suggested way, with the ground to the enclosure instead of the dc-jack input ground. From that, this showed on my multimeter on R6:

R6 (top): -8.99
R6 (bottom): -0.15

I measured the rest again using this method and edited my table of measurements on the first page!

[John Nada]

Maybe you're not getting a signal because it's gating. Have you tried swapping around the transistors?

Someone on the forum of Musikding (where I got the kit from) suggested that I try and switch Q1 and Q2. Just did that, but no difference unfortunately.

But today I started using a different amp for testing, which I started using for the audio probe. It's a bit easier because it has a headphone jack and it's a cheap thing, I didn't want to be messing around plugged into my tube amp ofcourse. Anyhow, with the headphone on and the pedal engaged I hear some very low signal when I turn everything all the way up, which reflects with what I heard during my audio probe: that there is still signal leaking to the output. A high frequency was ofcourse easier to pick out than a guitar signal.

[John Nada]

My 2 cents says R6 is not really connected at both ends.

Regarding that comment, I'm having a 'light bulb moment'. Correct me if I'm totally of here:

What I did notice though, is that Q1 gets powered by R4, which has more than -8v on both ends, Q3 gets powered by R10 which has more than -8v on both ends, but Q2 (where the issue seems to starts) has -8v on one end and just -0.15v on the other. Isn't that just the issue, the reason why the volume drops after C2? Either the resistor losing its incoming power (broken resistor?), or that one end isn't soldered properly and doesn't put out enough power, dropping the signal's volume going into Q2?

Not sure if that makes sense, but as far as my newcomer-brain can comprehend and putting the results of my multimeter and audio probe testing, this makes sense somehow. Hoping you or someone can tell me if this actually does.

[Electric Warrior]

My 2 cents says R6 is not really connected at both ends.

Regarding that comment, I'm having a 'light bulb moment'. Correct me if I'm totally of here:

What I did notice though, is that Q1 gets powered by R4, which has more than -8v on both ends, Q3 gets powered by R10 which has more than -8v on both ends, but Q2 (where the issue seems to starts) has -8v on one end and just -0.15v on the other. Isn't that just the issue, the reason why the volume drops after C2? Either the resistor losing its incoming power (broken resistor?), or that one end isn't soldered properly and doesn't put out enough power, dropping the signal's volume going into Q2?

Not sure if that makes sense, but as far as my newcomer-brain can comprehend and putting the results of my multimeter and audio probe testing, this makes sense somehow. Hoping you or someone can tell me if this actually does.

No, the voltage on Q2's collector is perfect. It's meant to be biased around 0.16 V. Here are voltages from a great sounding vintage unit for comparison:

Battery: 9.67V
Q1 C -9.02V B -0.03V E 0V
Q2 C -0.17V B -0.08V E 0V
Q3 C -8.44V B -0.17V E -0.11V

I'm not sure what it should sound like in that spot, though. I never used an audio probe.

[aelling]

Have you checked if you have the pots swapped? B1K is Attack, A100K is Volume.

[John Nada]

Have you checked if you have the pots swapped? B1K is Attack, A100K is Volume.

Just re-checked this, but the pots are correct how I have them now.

[aelling]

What about the power supply you're using? Are you using the correct polarity as this effect is Positive Ground?

[John Nada]

Someone at the Musikding-forum (from the webstore where I bought the kit) suggested I resolder C4 again. Even though both ends still give a loud signal during the audio probe (it was the last thing in the chain that still gave the loud signal), he said that with an audio probe you force the pins and that one of these solder points looked a bit cold. So I did as he said, resoldered C4 again and now it works and sounds great!

Thanks everyone so much for helping me out here, I learned a lot and it won't be my last post here, since I'm building some more.

[Electric Warrior]

Oh, interesting. Your solder joints looked so good, a bad joint would have been my last guess.
Enjoy your Tone Bender 

[PRR]

> Your solder joints looked so good

The blobs are nice and shiny.

Looking close (closer than I did before), there's no proof the solder "wet" the parts leads in some points.

Looks like tarnished leads. (Some have the lead-stub blobbed-over so we just can't know.)

Get the leads (and PCB) VERY clean. I normally pre-tin leads to be sure they are solderable and the solder is fresh like tomatoes from your garden.

If this came to me, wonky, I'd heat-and-beat most of the solder off, scrape the leads, re-tin in strong light with magnifier, then do taut tight wet joints.