# Low tide no modulation.....



## nickquack (Mar 5, 2022)

Wished Id never had to post here, but here we are.

Bypass, mix, and level knobs work well. Gate knob is kinda weird, seems to respond to the trimpots? But the main issue is I'm getting zero modulation motion on the pedal on any knob setting, even after trying to bias the BBD.


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## JamieJ (Mar 5, 2022)

Where did you source your BBD?
These huge circuits are very difficult to remotely troubleshoot. The first thing I would do is to check all resistor and cap values. Try some other 3207s if you have them.


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## bowanderror (Mar 5, 2022)

It sounds like the preamp & output portions of the circuit are working OK, so that leaves either the Gate, BBD, or modulation sections.

The first thing you'll need to do is to make absolutely sure you have the Gate & Bias trimpots set properly. Unfortunately, they both have quite narrow usable ranges (especially on the Gate trim), so make very, very small adjustments with a screwdriver. I  posted this on another thread, but here is info I've collected on setting the trimpots:

*BBD/BIAS trim pot* - _Set for loudest, cleanest sound_

Set your Slew control to 0%, Mix, Gate, & Depth to 100% and Rate to ~50%
Set both DIP switches to their OFF positions (to the left on your pic) - You can choose which DIP switch to use after setting up the Gate trimpot, but you should only be using either the Boost OR the Pad switch, not both at the same time.
Turn up the Level control to where it's loud enough to clearly hear the signal
Start with the trimmer at noon (50%) and gently adjust right & left to find the "sweet spot" where the signal is the loudest & has least amount of distortion. There is a range on the trimmer where you will hear the chorus/delay effect. At either end of the range, there is quite a bit of fizz. Pretty obvious when set correctly, just set the trimmer for the least noise & fizz.
*GATE trim pot *- _User preference_ - Controls the frequency of the low pass filter portion of the gate, and how much it's envelope is triggered by your input signal (interacts heavily with external Gate control)

The Boost & Pad DIP switches will change the sensitivity of the Gate to your guitar signal, so decide if you want to use either before setting the Gate trimpot. Otherwise, keep them both OFF - I keep the Boost switch ON at all times, because it has a more drastic effect on the Gate, and the preamp has a nice lofi sound.
Set Mix to 100% wet, Gate & Depth to 0%.
Set the Gate trimpot to 0% to start.
Slowly turn Gate trim clockwise, you should hear the filter "open up" as you turn the trimpot up.
After each Gate trimpot adjustment, try the external Gate control at settings of 0%/50%/100%. You want to set the Gate trim so the external Gate knob goes from completely off at 0% to completely open at 100%, with a good amount of different settings in between.
*GATE trim setup from Fairfield Shallow Water Manual:*

*LPG ADJUST (i.e., GATE TRIM) *- The recovery filter’s lowest frequency can be adjusted, to fine tune the way it will react to incoming signals. Lowering this frequency emphasizes the action of the low pass filter, effectively raising the threshold of sensitivity. Adjustment should be made with the following settings: MIX full wet, LPG minimum, DEPTH minimum. While listening to a signal going through the pedal, you’ll hear the effect of the recovery filter at its resting state. Carefully turn the trimpot labelled LPG adjust (i.e., GATE TRIM), clockwise to raise the filter’s frequency, counter-clockwise to lower. Be very careful, adjustments should be minimal as the trimpot is very sensitive. After each adjustment, LPG should be turned up momentarily to listen at the envelope’s response to the incoming signal.
If you still don't have any modulation after setting both trimpots, I would use a multimeter to record the voltages at each of the IC pins, and take a closer photo of the text on your 3207 & LM13700 chips.


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