[SOLVED – bad trace] Moodring: gain recovery stage isn't recovering gain

[benlanc]

I'm having some issues with my Moodring; I'm only getting dry, unaffected signal out. So, I started with the audio probe and followed the affected signal out of the Belton, through the tone control and to pin 5 of IC4. All good so far.

When I checked for signal on the way out of Pin 7, I got nothing at all.

Voltages on the "A" side of IC4 are fine, however on the "B" side I get 1.5V at Pin 6, and 8.5V at Pin 7 with a supply voltage of 9.1V at Pin 8.

Component values and electrolytic capacitor orientation for the feedback loop around the inverting input look right to me. The only thing I noticed that seems suspicious is that the trimmer seems to have no effect on the output.

Any pointers??

[benlanc]

I did some continuity checks with the DMM and for some reason I didn't have continuity with Pin 7 of IC4 and C24 or pin 2 & 3 of the trimmer.

Reflowing the joint didn't help so it looks like there's a problem with a trace on the board. I ended up having to desolder the Belton (not a fun job, ruined the +5v pad in the process and had to run a wire to Pin 1 of the PT2399) and putting a jumper in to bridge IC4 Pin 7 to C24.

Suffice to say, now this thing sings. What a beaut!

Brian, have you had any problems with any other Moodring boards or was I unlucky? All the soldering around there looks pretty decent so I'm not sure how I would have damaged it.

[jtaormina]

I just finished one a couple weeks ago and it fired up first try. I think you got unlucky.