Problems with Sweet Honey - help, please!

Posted by ChristopherM on Dec 29, 2014; 4:07pm
URL: http://guitar-fx-layouts.238.s1.nabble.com/Problems-with-Sweet-Honey-help-please-tp15998.html

Hmm … I can’t get a sound out of this, so I’m hoping that someone can give me inspiration about the solution.

Audio probe traces the signal only as far as pin 2 of the OP275 (and it is not full strength even then). There is nothing at pin 1 or anywhere beyond.

DC voltages at OP 275 with pots full up, no input, output unloaded and 9.4 V supply are –
1 – 4.24
2 – 4.34
3 – 4.32
4 – 0.00
5 – 4.25
6 – 4.38
7 – 4.38
8 – 8.54

I checked all component values except OP 275 prior to build (and in situ as far as possible). I’ve checked for shorts between traces and I’ve even checked continuity of traces. I’ve reflowed all solder joints. I’ve checked layout carefully and even cross-checked against the circuit schematic.

Although the DC voltages on the op amp don’t seem too strange, I’m wondering whether I’ve fried the op amp – it’s not socketed, unfortunately. Anybody got any thoughts about this or what else might be the problem?

The only deviation that I am aware of is that I have no indicator LED connected, but I can’t see that would make any difference to the function of the circuit.

Any help gratefully received!