Stripboard Buffer pedal - low signal problem

[dbargaehr]

Hey everyone,

Been a while since I worked on any stompboxes, but a friend asked me to build him a buffer. After a bit of research, I chose this simple veroboard layout below:



I believe it's a Klon buffer variant?

Plugged it in and got probably 20% signal, very weak. As soon as I bypassed it, back to full signal - tried swapping cables, amps, etc. to make sure it was definitely the pedal.

I checked and retouched the solder joints, made sure power was fine (+9.2V, tested it on my multimeter), and made sure no strips were unintentionally bridged. Also made sure I hadn't wired the jacks backwards or any other general dumb mistakes.

There's only two changes I made - I used an non-polarized capacitor for C2, which is a DC filtering cap and doesn't need to be polarized, correct? And I also used 2.2M resistors on R1/R2 to raise the input impedance.

Is the non-polarized cap the issue, or is it possible I have a bad TL071? I don't believe I burned it out, I was pretty quick with the soldering. Before I order another TL071, does anyone have an idea of how I screwed it up? 

[R.G.]

I believe it's a Klon buffer variant?

??
Klon buffer variant? It's about as plain vanilla an opamp buffer as can exist.

Plugged it in and got probably 20% signal, very weak... Before I order another TL071, does anyone have an idea of how I screwed it up? 

I believe that your mistake was not looking at the datasheet for the TL071. Pins 1 and 5 on the 071 are offset null pins. You have pin 5 tied to ground, I think. First, isolate pins 5 and 1 from anything else. That may not be THE problem, but it's certainly one you may run into.

[dbargaehr]

??
Klon buffer variant? It's about as plain vanilla an opamp buffer as can exist.

You're right - I looked it up, and I was mistaken - it's a Doobtone, except the Doobtone uses an LM741. Same pinout as a TL071.

I believe that your mistake was not looking at the datasheet for the TL071. Pins 1 and 5 on the 071 are offset null pins. You have pin 5 tied to ground, I think. First, isolate pins 5 and 1 from anything else. That may not be THE problem, but it's certainly one you may run into.

Fixed it! Definitely a bad opamp - swapped it out and it worked fine - even with pin 5 tied to ground. Wonder why that is...thanks man!