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Hey guys, recently had a request from someone to add a rate LED to a Polytrog I build for them. I assume it will follow the "rate" pot if I put it in parallel with the LDR LEDs? If I do this, should I put it after all of the vactrol LEDs and then lower R42 to ~250R? This is a complex circuit compared to what I normally mod, so want to make sure I cover my butt before I start poking around in it!

If I wanted it to pulse with the "mod rate" pot, where would be the best place to tap into that voltage? Thanks!

For the Rate pot you would put the LED in series with VC1-3_L, nt in parallel. Lowering R42 might compensate or prove unnecessary. For the Mod_Rate I'd try a 10k CLR and LED connected to pin7 of IC9_B first. Do it on a breadboard where you can easily disconnect the LED and see if it impacts performance.

These are just educated guesses.

This person is actually requesting another one built as a backup, and wants both the rate and mod rate slowed. They tested it against their own Polyphase and claim it's 2-3x faster as built, I didn't have one to test against but they sent recordings and it is indeed much faster even at minimum. The LFO section of this is pretty complex to my novice eyeballs, I'm going to see how the second one I built sounds stock but if I need to decrease the rates, is decreasing the pot values the way to go or would they need to be larger (which is not available probably, as they're both 1M lol)?

Yep! Relay is definitely working, the bypass board itself appears to be working as the LED turns on and there is a n audible blip in the signal upon turning on, similar to other VFe pedals I've built. I was initially thinking somehow I had messed up the bypass boards since I built them together, but I also built a Tractor Beam at the same time and that's working fine... very strange.

One breakthrough, though the mystery continues...

I didn't think I had any other single op-amps on hand but then I realized that I had a CA3130EZ. I popped it in and that solved the voltage readings on pins 1 and 5 of the IC! Pin 6 was still off (more on that later) but I figured I'd plug in and give it a shot.

The pedal basically works now. I built a Naughty Fish a few years ago so I'm familiar with what to expect from all the knobs and switches. I noticed a bit of extraneous interference-type noise which was probably just due to the open enclosure. However, there's a lot of scratchy/static noise when I turn the level knob. Maybe this is related to the fact that I'm seeing DC voltage (~4v depending on level knob setting) on pin 6 (output).

So two questions remain:
1. What's the likely source of the DC voltage on pin 6, and is there any chance this is related to the CA3130EZ substitution?
2. How in the world did I end up getting two OPA134s from Mouser that didn't work correctly? I've ordered parts from them for years without encountering this kind of problem. I can't imagine that these are fakes (see pictures).

Thanks again, everyone!

Ok I missed this... that solved my voltage issue but not the overall problem I'm having.

I'm working through a pile of boards that I finally got around to, I'm having some weird results with both the Mobius Strip and Mini Mu. Both are just passing clean signal, bypassed or not, and no controls appear to do anything on either. The switching board works and LED lights up etc. On the Mobius Strip, all voltages match up to those posted in the build doc, on the Mini Mu (I've built this pedal before, so extra frustrating here lol), everything is right EXCEPT pins 1 and 5 of the OPA134 should both be ~ -8.5 V and are +8.2 V and 0 V respectively *EDIT - this is from a bad OPA134, switching it out fixed the voltages but not this issue*. Pictures of both builds attached here. I've built probably 10-15 VFe pedals and have never had this issue before. Any input is appreciated!

Derek

Thanks, all! I inspected the board and couldn't find any solder bridges. However, I did see that I missed one of the socket pins for the TLE2074, so I soldered that (and reflowed anything that looked like it could use it). I'm now getting sound when the pedal is engaged, though the envelope effect is barely noticeable and the up/down switch doesn't seem to make a difference. Here are my new voltages with ICs installed. In summary the TLE2074 seems fine, the LM358 seems fine except for pin 2, and the OPA134 has a few anomalies (pins 1 and 5, in particular). Any ideas?

IC1 OPA134
1   8 (should be -8.4)
2   0 (should be 0)
3   0 (should be 0)
4   -8 (should be -8.4)
5   0 (should be -8.4)
6   0 (should be 0)
7   8.3 (should be 8.
8   8 (ignore)

IC2 LM358
1   7.1 (should be 7.57)
2   0.03 (should be 2.24)
3   4.1 (should be 4.35)
4   -7.9 (should be -8.44)
5   0.02 (should be 0.027)
6   0.03 (should be 0.03)
7   0.5 (should be 0.36)
8   8.3 (should be 8.

IC3 TLE2074
1   0 (should be 0)
2   0 (should be 0)
3   0 (should be 0)
4   8.3 (should be 8.77)
5   0 (should be 0)
6   0 (should be 0)
7   0 (should be 0)
8   0 (should be 0)
9   0 (should be 0)
10  0 (should be 0)
11  -7.9 (should be -8.4)
12  0 (should be 0)
13  0 (should be 0)
14  0 (should be 0)

Were you ever able to find your issue? I've built this pedal a few times before with no issues but I am getting the same voltage problems you are on the OPA134, all other voltages check out. Pedal just passes clean signal even when it's on, no controls affect anything. Interestingly from the schematic... those pins (1 and 5) aren't attached to anything that I can see, though the VFe schematics are often a bit of a nightmare to deconvolute lol.

Thanks Brian! I'll test em out and see how it goes, I'll report back

Hey guys, recently had a request from someone to add a rate LED to a Polytrog I build for them. I assume it will follow the "rate" pot if I put it in parallel with the LDR LEDs? If I do this, should I put it after all of the vactrol LEDs and then lower R42 to ~250R? This is a complex circuit compared to what I normally mod, so want to make sure I cover my butt before I start poking around in it!

If I wanted it to pulse with the "mod rate" pot, where would be the best place to tap into that voltage? Thanks!

Where is your level pot set in all this? Let's double check the values of R2 and R3, too.

The level pot was about halfway up, R2 measured 100k and R3 was 22k, in line with what they should be.

Yep. Here's a video https://youtube.com/shorts/inqz-aI8We4?si=x9yJRU85KNZlmw8G

Finished up my Skoolie build and can definitely get some good sounds out of it but I'm getting distortion on the repeats as well as the dry signal even in bypass mode. I did the testing (everything was fine here) and calibration (some issues here) as suggested in the build doc. When setting the bias of IC8 (the first MN3005) I could never really get the repeats clean. They were distorted through the entire range of the bias trimmer until I lost audio at the extremes of the trimpot. No issues with anything after that in the testing, I'm not sure if this is a gain issue elsewhere possibly? I'm getting the overload LED on basically every note when playing through it as well. Any help is appreciated!

FYI, I bought a bunch on Mouser while they were backordered and just got them, so they may be in stock on the site now too. Might not have to wait for November.

Oops, yes, sorry. Currently building a Retrograde as well, that uses the TM022, managed to combine them for this question lol. The 42TL002 is what I'm looking for and is very much impossible to find as far as I can tell. It's backordered on Mouser with expected availability in November

Not sure if this is the right area of the forum to post this - anyone have any idea where to source 42TL002 transformers? I'm building a PedalPCB Octanaut and all of the usual (and some of the unusual) suspects are either backordered or don't have this particular transformer at all. Also open to suggestions for substitutes. Thanks!

Bumping this, I can't seem to find these anywhere

Anyone (@madbean) have suggestions as to where to buy the 2 pin connectors used on this build? I bought it and it sounds awesome, I would like to start using them on other builds as well where possible since it's just much neater and makes removing the board much easier if necessary. Thanks!