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Pork Barrel Help

Started by resansom, September 03, 2019, 07:35:07 PM

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resansom

Hello, I just finished my first Pork Barrel build and am getting no sound, at output.  Using an audio probe, I am getting clean signal on pin 3 of the Blend control and chorus signal on pin 1 of the Blend control, but I get nothing after either 20k resistor (R45 and R46). I have replaced the 4558 op amp (IC1), to no avail.  Voltages appear to be OK, and the vast majority of the circuit is working, just fine - it's just the last part of the circuit, after the Blend control that is not working.  Has anyone encountered this problem?  Does anyone have any ideas on how I might continue troubleshooting?  I'm just about out of ideas... Thanks, very much.  :)

somnif

Can you take a picture of the board? A fresh set of eyes may notice a problem you have missed.

madbean

It's normal to get signal with an audio probe on pins 3 and 1 and NOT on R45 and R46. With an audio probe, you do not get audio when going into the inverted input of an op-amp (here pin6 of IC1).

So, your problem most likely lies between pins 6 and 7 of that op-amp. If you have no signal at pin7 then something is definitely amiss. Need to look at soldering very carefully, check for anything that looks wrong on the PCB itself (use the trace guide in the doc), check values for R10 and R11.

resansom

I'll take a picture later today and upload it - thanks, somnif.

Also, thanks madbean - there is no signal at pin 6 or pin 7.  I'll re-check the soldering there and on the feedback components between pins 6 & 7, too.

Much appreciated!

resansom

Wasn't able to do any more troubleshooting, but I do see some suspect soldering/possibly cold joints - I just got a new soldering iron, so I'm going to re-wet some of those joints.  I'll let you know if/when I'm able to figure out what is wrong.  Thanks, again, for your help.