Dr. Phybes no signal out of IC1 (solved)

[Anonymous]

Hi all, I hope everyone is doing well.

I wanted to get some confirmation before I start swapping out parts. I’ve built a Dr. Phybes (with the 45 and rate LED mods) but I’m getting no signal out. I’ve done a trace and the first problem is I’m getting no signal coming out of pin 6 of IC1. I have 9.4v at pin 7 (Vcc) and getting signal coming into pin 3 (IN+). When I check pin 2 (IN-) I also hear nothing (I’m guessing because nothing is coming out of pin 6 to feed back to pin 2).

What I’m wondering is, is there anything else I should check before I replace IC1 (a TL071 I bought here at guitarpcb)? And, if I replace it and I’m still not getting any signal, what’s the next thing I should check?

Thanks!

[Anonymous]

I also tested Q5 (2N4125). I thought maybe this had something to do with it. I didn’t hear anything but I’m getting these voltages:

C=2.4v

B=3.6v

E=4.2v

[Billy]

Mike remove IC1 from its socket and reflow the solder joints  what voltages do you get on pins 2,3,6

[Anonymous]

Thanks Billy! I reflowed all the joints on IC1s socket. Still no audio coming from pin 6.

My voltages are:

2 – 4.16v

3 – 4.02v

6 – 4.16v

7 – 9.45v

VB is 4.2

[Anonymous]

If you have done the steps Billy suggested and you still have no signal at pin 6, May I suggest you swap the TL071 from IC1 and IC3.  If the one from IC3 works in the IC1 position, you have a bad TL071.  Your voltages and signal present at pin3 suggest that this may be the issue.  Verify continuity at pin 6 between the socket and the board trace.  Your reflow should have ensured that.

[Anonymous]

Yes sir! Looks like that was it. I replaced the TL071 with TL061 from IC3 and I have proper signal flow. Thanks for the suggestion. I’ll update when I get the new part in.

Thanks y’all!

[Author]

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