Circulator (rev.2) No Modulation

[djmiyta]

I'm getting basically a very slightly filtered signal when engaged. Turning any of the pots does nothing. Flicking the toggles does nothing> I'm getting voltage to all the IC's ( although I'm not sure what they should be) on all + supply pins I get 9v . I don't know how to check if the LFO part is working can anyone tell me how I can check if LFO section is working properly aside from using my ears?

 

[Chuck D. Bones]

I would not change out the LM13700 just yet. Do you have breadboard capabilities? If so, you could breadboard the LFO and test your other LM13700s. The throb LED is still not flashing, correct?

FYI, I bought some LM13700s on Amazon and they work fine. Like it or not, workmanship is still the prime suspect.

 

[djmiyta]

I would not change out the LM13700 just yet. Do you have breadboard capabilities? If so, you could breadboard the LFO and test your other LM13700s. The throb LED is still not flashing, correct?

FYI, I bought some LM13700s on Amazon and they work fine. Like it or not, workmanship is still the prime suspect.

Correct the throb LED is not flashing and when I replaced C13 & 14 it seems to be less phasing (when manually rotating the pot) then with the electrolytics.
And though I’ve gone over the values a few times I still feel there’s a wrong value in there somewhere so gonna check again. And although I completely agree about my workmanship I have made some extremely sloppy builds that worked absolutely fantastic that probably by all rights shouldn’t have. I’m not positive but my guess is some circuits or it’s the layout are much more forgiving than others and why I’ve been lucky. I’ve been building for years but solely for myself. When l bought a non working Dr. Q for $6 years ago and I remember thinking damn what a mess, long thin wires, the circuit board looked home made, I soldered a broken wire back on the only place it could go and BAM it worked and I was hooked. I’m not knocking anything about workmanship but I’ve found it to be a problem only on larger builds and back when all my pots were wired rather than on board. I have NO problem with and AM asking if you and other members WOULD point out mistakes things they see wrong or wouldn’t do. It can only make my future builds better I take criticism as lessons not personally so please everyone fire away I’d love to get this working I’ve 1 more to troubleshoot and all 80 of my pedals will be (to and for me) 100% working
Then I can build more.
Although I’ve got like another 40 builds waiting for homes that don’t warrant being boxed to my ears but not bad enough to scrap
Wow once again I ramble on sorry about that

 

[djmiyta]

And sorry I do not have a breadboard. Can I do it without one? Or jimmy rig something together? I’ll upload some more pics with the mods done maybe it will help?

 

[Chuck D. Bones]

I looked at IC3's voltages and one in particular stands out. Pin 12 should be lower voltage than pin 14 and it's not.
In the photos, it looks like IC3's socket is resting on R2. Is that true? Are you sure that the socket pins all have good connections to the board? IC3-12 looks a little wonky in the photo. Are you sure the pin is fully engaged in the socket and not curled under?

 

[Chuck D. Bones]

And sorry I do not have a breadboard. Can I do it without one? Or jimmy rig something together?

Let's not go there.

 

[djmiyta]

Let's not go there.

Sounds good to me. I’ll have to check later tonight about the other stuff

 

[djmiyta]

There is one mod I didn’t do and that’s the diode one. Think that one would help. I also have to double check my mods (just in case you never know)

 

[djmiyta]

Also would audio probing help at this point. Probably not since it’s just a locked up LFO correct?

 

[djmiyta]

Cleaned board. Replaced jacked up caps. Took new voltages. IC3 voltages have changed but the phase is still not working correctly only still manually . And IC3 pin 12 is now .33 volts over pin 14 where it was only .2 volts before. All the pots and switches seem to do what they’re supposed to as far as I know just no auto sweeping