SOLVED Low Tide (Full Size) Oscillator problem

[Jachiro]

Hi. I recently put my Low Tide modulator and I'm having some pretty nasty trouble with it. I'm unable to get a proper wet signal. I have set the bias point of the V3207 BBD to a healthy 2.5V (1/2 of the 5V going to the VDD terminal). At this bias point I should get something on the output but I don't get a wet signal.

My settings for trying to bias the bbd is 100% depth, 100% volume, 100% Mix, 50% rate, 0% Gate, 0% Slew. Here are my observations on troubleshooting so far.

No wet signal at all. But when I turn the gate trimmer past halfway, I get a nasty loud oscillation at the output. If I move the gate trimmer back closer to zero, it goes away.

I am definitely getting a good signal past Q1, Q2, and I am getting an input at the BBD on pin3. At the output, I am getting an extremely distorted output on pins 7 and 8.

Right now, I have disconnected the MCP602 IC to help isolate any trouble with the randomizer part of the circuit on though the CD4046 PLL chip. I still get the distorted output at the BBD and the oscillator.

I could really use some advice on how to go forward with troubleshooting. I put this circuit together carefully and I have had numerous successful builds in the past, including a mini low tide (which I sold last year). I've already spent quite a few hours in solving this problem on my own, but I could really use some advice. Thank you so much in advance for any expertise.

 

[inflatablerobot]

Double check the Q1, it kinda looks like your 2SK208 transistor is in backwards.

 

[Jachiro]

Hi. It does appear that it’s backwards. During my troubleshooting, I accidentally pulled my surface mounted Q1 and destroyed the pads. I ended up substituting another sk series transistor; I twisted the gate and source legs to go into the proper pads making it appear backwards. Q1 is actually working fine and amplifies and passes signal as it should.

As an update, I ended up causing damage to the board by desoldering and desoldering too many components; in particular, the IC’s. I decided to purchase a new pcb and starting over. I will build it slower and more carefully this time. Hopefully, I’ll not run into the same issues next time.

I’ll keep this thread open since this is a challenging build and I will no doubt have questions when it comes time to dial in the trimmers.

 

[Jachiro]

Ok, new update. I ordered a new pcb and started over. I was 100% sure all my values were correct per the documentation. I also made sure to use sockets instead of soldering IC's directly to the board in case I needed to replace one or more with no risk to damaging the PCB. I got very different results this time and everything worked out for me. Here are my notes on dialing in the trimpots:

1. Do the GATE adjustment first - Set the mix to 100%, Depth and Slew to zero and Volume all the way up. Start with the trimpot all the way turned to the left and slowly turn it up. Plug in a guitar and start playing. You'll hear a point where the gate "kicks in" and you'll start to hear the sort of "underwater" effect of the filter. From this point forward, make very small adjustments and turn the GATE knob all the way up and down after each adjustment. You should hear a good wide range. All the way clear (it can overdrive) when the gate is all the way up, to fully underwater and with a "woh" kind of quality to the sound with the gate all the way down. Once you feel like you have a nice range - it's done. Move on

2. BBD Bias adjustment: You'll need the GATE control to be set at a point where you can clearly hear the modulated signal. You can set the depth all the way up and the rate to wherever you like. I recommend at least halfway just so you can hear the sweeps more often. Volume and Mix up. Here you can just play and adjust the trimpot up and down until you hear a good modulated signal with no distortion. Just like other posts have said about this adjustment, it's pretty intuitive and easy to know when you have it set right. I like to use an oscilloscope at the output pin of the BBD and look for the largest wave with no clipping.

Additional notes: This wasn't my first rodeo building time-based effects pedals. The documentation for the Low Tide Modulator is pretty good, but it really needs to include a short paragraph or two about how to bias the trimpots. I've built pedals using Aion PCB's, Madbean, and LectricFX PCB's and documentation is excellent with a lot of information about bias adjustments. I think the forums are fantastic for getting great minds together and working through troubleshooting on pedals and amps, but in this build, I used the forum itself to find the bias procedure for this project based on troubleshooting posts. I think it was more difficult than it should have been.

With all that said, I really hope my post is helpful to the next person who decides to build this pedal. It's absolutely doable, but you have to tread very carefully to avoid donking it up.

 

[Erik S]

With all that said, I really hope my post is helpful to the next person who decides to build this pedal. It's absolutely doable, but you have to tread very carefully to avoid donking it up.

Congrats on getting it working!

Nice write up too - I bookmarked this post for when I get around to building mine.

 

[Jachiro]

Congrats on getting it working!

Nice write up too - I bookmarked this post for when I get around to building mine.

Feel free to reach out if you have any trouble.

 

[Mr. Met]

With all that said, I really hope my post is helpful to the next person who decides to build this pedal. It's absolutely doable, but you have to tread very carefully to avoid donking it up.

That's me, just finished my Low Tide, thanks for summarizing the trim and tuning steps!

 

[BlackLab]

Thanks so much for the write up….you just saved my build …thanks

 

[giovanni]

Ok, new update. I ordered a new pcb and started over. I was 100% sure all my values were correct per the documentation. I also made sure to use sockets instead of soldering IC's directly to the board in case I needed to replace one or more with no risk to damaging the PCB. I got very different results this time and everything worked out for me. Here are my notes on dialing in the trimpots:

1. Do the GATE adjustment first - Set the mix to 100%, Depth and Slew to zero and Volume all the way up. Start with the trimpot all the way turned to the left and slowly turn it up. Plug in a guitar and start playing. You'll hear a point where the gate "kicks in" and you'll start to hear the sort of "underwater" effect of the filter. From this point forward, make very small adjustments and turn the GATE knob all the way up and down after each adjustment. You should hear a good wide range. All the way clear (it can overdrive) when the gate is all the way up, to fully underwater and with a "woh" kind of quality to the sound with the gate all the way down. Once you feel like you have a nice range - it's done. Move on

2. BBD Bias adjustment: You'll need the GATE control to be set at a point where you can clearly hear the modulated signal. You can set the depth all the way up and the rate to wherever you like. I recommend at least halfway just so you can hear the sweeps more often. Volume and Mix up. Here you can just play and adjust the trimpot up and down until you hear a good modulated signal with no distortion. Just like other posts have said about this adjustment, it's pretty intuitive and easy to know when you have it set right. I like to use an oscilloscope at the output pin of the BBD and look for the largest wave with no clipping.

Additional notes: This wasn't my first rodeo building time-based effects pedals. The documentation for the Low Tide Modulator is pretty good, but it really needs to include a short paragraph or two about how to bias the trimpots. I've built pedals using Aion PCB's, Madbean, and LectricFX PCB's and documentation is excellent with a lot of information about bias adjustments. I think the forums are fantastic for getting great minds together and working through troubleshooting on pedals and amps, but in this build, I used the forum itself to find the bias procedure for this project based on troubleshooting posts. I think it was more difficult than it should have been.

With all that said, I really hope my post is helpful to the next person who decides to build this pedal. It's absolutely doable, but you have to tread very carefully to avoid donking it up.

I just used this procedure on my brand new build and it worked flawlessly! Much better than setting it by ear.

 

[Jachiro]

I just used this procedure on my brand new build and it worked flawlessly! Much better than setting it by ear.

I’ve read comments here about my write up for the past year and a half or so. I’m happy it’s helping folks out. Lol it seems like it’s becoming the unofficial procedure.

I actually haven’t used my low tide in a good while. I’m trying to record a lofi track and I’m going to be putting the mix through this pedal. I’m looking forward to hearing how it’s going to mangle the sound

 

[Depattern]

I will make my own thread for this too probably but I wanted to ask for some help here since you seem to have a good handle on the expected behavior of this pedal. I've been a fan of the Shallow Water for a long time but never tried it. So i think i know what the expected sound should be,but Im having some major issues here with mine:

1. I hear pretty much 0 modulation unless I manually modulate the amplitude of the incoming signal (outside of the pedal). So here im sending in triangle waves from the sh-101 clone, and the only time i hear modulation, is when i tweak the volume on the synth going into the pedal. when i do that, its pretty extreme, but I cant get that effect otherwise.

when i dial the BBD BIAS pot, it goes from very noisy buzzy fuzz to nothing, then an extremely short range where i almost hear a pitch warble when turning it at a certain point, but nothing obvious. i can see where the behavior might be sort of intended where the pitch modulation reacts ONLY to your playing dynamics, and i guess there isnt a wide dynamic range coming from the synth notes, nbut you'd think i would hear a difference in depth and rate from the lfo either way

2. the MIX effected sound is only within the VERY last like 5% of the MIX knob range. I only hear effected signal at the extreme clockwise end of that knob. I dont know if this correlates with the gate tuning or what, but i've experimented with that pretty extensively I feel like

3. The DEPTH, RATE, SLEW dont seem to have any effect. I am hoping that these modulation issue can be solved if i keep working away at tweaking the BBD trimpot, but it just doesnt feel like thats going to work

4. The gate itself is not as easy to figure out whats going on. I hear when it kicks in if i set it a certain way on the trim, but its not exactly "low pass filtered"/watery to completely open, although i do hear the lo pass effect and when the BOOST switch is set, it does behave like a low pass vcf envelope, or a real lpg sort of, but its a little tricky to determine what the actual range should be. ot too worried about this one, but im just not sure whether or not this is tied to the problem im experiencing with the lfo modulation

 

[Jachiro]

I will make my own thread for this too probably but I wanted to ask for some help here since you seem to have a good handle on the expected behavior of this pedal. I've been a fan of the Shallow Water for a long time but never tried it. So i think i know what the expected sound should be,but Im having some major issues here with mine:

1. I hear pretty much 0 modulation unless I manually modulate the amplitude of the incoming signal (outside of the pedal). So here im sending in triangle waves from the sh-101 clone, and the only time i hear modulation, is when i tweak the volume on the synth going into the pedal. when i do that, its pretty extreme, but I cant get that effect otherwise.

when i dial BBD BIAS the pot, it goes from very noisy buzzy fuzz to nothing, then an extremely short range where i almost hear a pitch warble when turning it at a certain point, but nothing obvious. i can see where the behavior might be sort of intended where the pitch modulation reacts ONLY to your playing dynamics, and i guess there isnt a wide dynamic range coming from the synth notes, nbut you'd think i would hear a difference in depth and rate from the lfo either way

2. the MIX effected sound is only within the VERY last like 5% of the MIX knob range. I only hear effected signal at the extreme clockwise end of that knob. I dont know if this correlates with the gate tuning or what, but i've experimented with that pretty extensively I feel like

3. The DEPTH, RATE, SLEW dont seem to have any effect. I am hoping that these modulation issue can be solved if i keep working away at tweaking the BBD trimpot, but it just doesnt feel like thats going to work

4. The gate itself is not as easy to figure out whats going on. I hear when it kicks in if i set it a certain way on the trim, but its not exactly "low pass filtered"/watery to completely open, although i do hear the lo pass effect and when the BOOST switch is set, it does behave like a low pass vcf envelope, or a real lpg sort of, but its a little tricky to determine what the actual range should be. ot too worried about this one, but im just not sure whether or not this is tied to the problem im experiencing with the lfo modulation

Hey, I’ll try to help you out. I have successfully built this circuit twice, one was the full size low tide and the other was the low tide mini. There’s a few build notes to observe

1. Your chips should ALL be socketed. If any of your chips are bad and/or fake chips from eBay, and you need to replace one, it is extremely difficult and high risk to try to replace them because the pcb is double-sided. De-soldering is extremely difficult and a headache to do.

2. To begin your troubleshooting, start with making sure that EVERY single electrolytic capacitor is oriented correctly. If any were installed backwards, it will cause problems or make your circuit completely not work.

3. Next thing to check is that all your supply voltages on every chip are correct. You will have to look at your schematic and check all your supply pins and make sure they have the correct voltages. There’s 5V and 9V in the circuit.

4. Once all the caps and supply voltages are verified good, then you can start troubleshooting your signals. No modulation could be several things, there’s the randomizer chip circuit, and the LFO

Hopefully this gives you a good place to start

 

[Depattern]

thanks for your help. ive done all that except im not sure i checked every supply voltage. im continuing my troubleshooting recaps over here (LINK),

but i'll put the summary here as well:

i am getting 1-3 on ic5 pin 7 and ic2 pin 5. but the A1m dual gang SLEW pot bottom outer legs are only sweeping from 0 to 324v. while the top outer legs sweep from 0 to 1m.

i dont know if this is a fault with the dual gang a1m pot from pedalpcb OR something to do with r39. i dont want to pull out r39 if i dont have to, so i wanted to ask for advice here first, to make sure im even looking in the right place. should i try pulling out the A1m, ordering a replacement and testing that? should i rip out/clip r39 and replace that? i checked the stripe pattern and its the proper markings for a 470k resistor for R39. is there somewhere else i should be testing?

If i go through this circuit with my audio probe, what am i looking for?

there shouldnt be any cold joints or anything like that. ive been very careful about that any hadnt had any such issues in my last 6 or so builds.

TO RECAP:

• DEPTH, RATE, SLEW have no effect on modulation
• MIX wet signal only present at extreme CW end of knob
• LPG responds correctly to input amplitude changes
• No continuous pitch drift/LFO behavior

What I've confirmed working:

• RANDOMIZER (IC2) pin 5: ramping 1–3.33V continuously, speed changes with RATE
• IC5 (MCP602) pin 7: oscillating between 1–3V on its own
• IC6 (CD4046BE) pin 16: 5.05V (correct, on 5V rail)
• IC6 pin 4 (VCO out): 2.46V
• IC7 (V3207D) pin 3 (clock in): 1.703V
• IC7 pin 4 (Vgg bias): 4.72V

Where the signal dies:

• IC4 (LM258P) pin 3: stuck at 2.36V regardless of RATE, DEPTH, or SLEW position
• IC4 pin 7: stuck at 1.782V, does not vary

The modulation signal is confirmed alive at IC5 pin 7 but is not reaching IC4 pin 3. Between those two points per the schematic I have SLEW 2 (second gang of the A1M dual-gang) and R39 (470K).


What I've checked in that section:

• Reflowed all solder joints on the SLEW pot - no change
• R39 color bands read correctly as 470K (yellow-violet-black-orange-brown)
• In-circuit resistance between SLEW 2 output leg and IC4 pin 3 reads ~490Ω unpowered - suspiciously low but may be circuit loading
• In-circuit resistance across SLEW 2 outer pins reads 26K–324K sweeping CCW to CW - also suspicious but again may be loading from surrounding circuit
• No visible solder bridges anywhere in that area under magnification
  
  I also swapped out the ic 2, ic4, and ic7 just to be sure, before i got these final results. all ic's are socketed.

I'm hesitant to start lifting component legs without being more certain of the fault location. my audio probe wont be helpful for modulation signals, i imagine. Has anyone seen this exact symptom: signal alive at IC5 pin 7 but dead at IC4 pin 3, and can point me to what to check next?

 

[Jachiro]

Hey, I’ll see if I can make a more substantive reply to you when I get back from my work trip.

For now, I had a thought about the randomizer chip. I believe its voltage source is from a 5V linear regulator. I’d check the orientation on that and also verify it has a solid 5V at its output. It should be easy to check. Good luck w your troubleshooting and I’ll check your post again in a couple of days!