Low Tide: No Modulation

93ryans

New member
I posted about this same build the other day, but that was a different problem and also wasn't really a problem at all, just me not tuning the thing properly.

So I'd tested this circuit before I boxed it and I believe it was working fine then. I boxed it today and suddenly there's no modulation anymore. The Mix, Vol, and LPG knobs are all doing their jobs, but I get nothing from Rate or Damp. I get almost nothing from Depth, except that there's some slight movement in the wet sound when I turn it, which immediately stops when I stop turning it.

I figure it's most likely related to the fact that I had to un- and re-solder the power and I/O jacks, but I don't know what could have gone wrong. I've triple-checked that the the polarity is correct. I did nick a box cap while re-soldering. It doesn't look too bad, but could that have screwed something up? It's the second from the top left in the photo.

I've got an unboxed Low Tide Mini that's making noise right now (working fine), so I tried swapping the Randomizer IC's between them with no effect.

The last strange thing I just noticed is that when I plug in the power connector the LED turns on briefly as the plug is going into the jack. I hadn't noticed before because I hadn't added the LED til I was boxing it. Could this be a sign of power or polarity weirdness?

Thanks for reading.
 

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PedalPCB

Admin (Robert)
Staff member
The last strange thing I just noticed is that when I plug in the power connector the LED turns on briefly as the plug is going into the jack. I hadn't noticed before because I hadn't added the LED til I was boxing it. Could this be a sign of power or polarity weirdness?

This is normal. When power is applied the LED will flash briefly while C21 charges.
 

93ryans

New member
This is normal. When power is applied the LED will flash briefly while C21 charges.
Thank you, that's good to know. Could a heat-damaged Rate pot cause this issue? If so then that's my working theory. I think that one might have gotten some of my iron while I was desoldering the power wires, and the resistances it's giving me aren't what I'm expecting. Though that might be due to its place in the circuit, I'm not too sure. The resistance between the 1st and 3rd legs are only about 0.7 K.
 

PedalPCB

Admin (Robert)
Staff member
The impedance of the other circuitry on the 5V rail is probably affecting your resistance measurement but you can check that the pot is functioning properly with a couple voltage measurements.

Power up the circuit and measure the DC voltage on lug 3 of the Rate pot. You should have around 5V.

Next measure the voltage on lug 2 of the Rate pot at minimum (you should measure near 0V), then measure the same lug again with the Rate pot at maximum. (you should measure near 5V).

If the voltage on lug 2 changes when you turn the pot you can look elsewhere, it's most likely functioning properly.
 

93ryans

New member
The impedance of the other circuitry on the 5V rail is probably affecting your resistance measurement but you can check that the pot is functioning properly with a couple voltage measurements.

Power up the circuit and measure the DC voltage on lug 3 of the Rate pot. You should have around 5V.

Next measure the voltage on lug 2 of the Rate pot at minimum (you should measure near 0V), then measure the same lug again with the Rate pot at maximum. (you should measure near 5V).

If the voltage on lug 2 changes when you turn the pot you can look elsewhere, it's most likely functioning properly.
Seems to be working fine in that case. Thanks.

While I was checking that I noticed that the positive lug from the DC jack was bridging to the 5V lug of the pot, and thus the entire 5V pathway in the circuit. It's a kind of loose jack right now, but that might have been happening on and off since I boxed it. I trimmed the pot lug so it wouldn't happen anymore, but could that have damaged any of the ICs?
 
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