SOLVED Low tide gate trim doesnt seem right

[Locrian99]

Alright so I just built a low tide. And theres something up with the gate.

I dont get any wet signal at any position in the the gate trim until its turned up to 3 o’clock (fully ccw being 8, fully cw being 4). Then i have a fizzy sound, fully cw it sounds open. I do have effect when fully cw. Its just limited sounding compared to previous ones ive built. Going to start checking resistor and cap values. If anything leaps out…
Link to scheme here: https://docs.pedalpcb.com/project/LowTide-Schematic-PedalPCB.pdf


My output from the trim ranges from apx 3.1v to 4.0 ish. My lm258 is reading 2.56 on pins 2 and 3, and 1.28 on pin 1. My usual answer to everrthing of just audio probe it, I don’t think will solve this one.

 

[ThatDude]

Are both the pad and boost switches in the on position in the photos you posted?

 

[Locrian99]

Are both the pad and boost switches in the on position in the photos you posted?

For some reason i thought to the left was off, and i can clearly see the on. So yes they are.

 

[BrainDrain]

For some reason i thought to the left was off, and i can clearly see the on. So yes they are.

I believe only one of them is supposed to be on at a time.

 

[Locrian99]

I believe only one of them is supposed to be on at a time.

Yea I thought i had them both off, but apparently i had them on…. Ill try them both off when i get home.

 

[BrainDrain]

Yea I thought i had them both off, but apparently i had them on…. I’ll try them both off when i get home.

Not sure if this could be the issue with how it’s acting but the gate on mine wasn’t working properly and it ended up being a broken trace under the solder mask. The pcb I got actually had two broken traces but once jumpered everything worked properly. It got me to start continuity checking all the traces on new pcbs just to eliminate it from the beginning now.

 

[Locrian99]

Not sure if this could be the issue with how it’s acting but the gate on mine wasn’t working properly and it ended up being a broken trace under the solder mask. The pcb I got actually had two broken traces but once jumpered everything worked properly. It got me to start continuity checking all the traces on new pcbs just to eliminate it from the beginning now.

Thats crazy ive built idk how many of the ppcb boards up and never had any issue. I suppose it happens just in case you remember where the trace was ?

 

[comradehoser]

I had an issue with the gate; turned out to be 100% error me: an incorrect resistor value at R48. So, as usual, visual inspection, double-checking all values to BOM, polarities, and quality of solder joints (especially the SMD) is step 1.

 

[Guilherme Collateral]

On a side note, that mn3207 looks suspicious to me

 

[Locrian99]

On a side note, that mn3207 looks suspicious to me

Those 3207’s ive built many caesars, cepheids etc without issue from that batch. Yes they are sourced from ebay. But every one has worked great.

Ear test comparison with a known legit 3207 pulled from an 80’s peavey amp i could hear no difference on a previous build (was curious).

 

[BrainDrain]

Thats crazy ive built idk how many of the ppcb boards up and never had any issue. I suppose it happens just in case you remember where the trace was ?

It doesn’t seem common. I’ve built a bunch of these and the only other one it happened on was the Dirt Dauber. Defective trace after the protection diode so nothing was being powered. So other than these two they’ve all worked perfect and sound great.

These were the two traces on my board that had no continuity.



Here’s the thread documenting it all:
My Low Tide Journey

 

[Locrian99]

Are both the pad and boost switches in the on position in the photos you posted?

Was really hoping this was it… nope
Same thing no matter where the switches are.

Although upon further looking i think i put the switch in backwards.

 

[ThatDude]

Was really hoping this was it… nope
Same thing no matter where the switches are.

Although upon further looking i think i put the switch in backwards.

Darn it! I was hoping to help you figure it out. Back to the drawing board.

 

[Locrian99]

Darn it! I was hoping to help you figure it out. Back to the drawing board.

Currently going through and verifying color codes and capacitor codes one by one, tried another lm13700 for s&g’s from thr schem it looks like really only it and the 258 have any thing to do witj the gate ic wise.

Ill probably reflow as well.

 

[Locrian99]

Ok so ive reflowed everything other than whats under the slew. Double checked all values past the gate pot to lfg control.

I’m not sure what im looking for voltage wise in the lm13700, however 9 and 10 look suspect for sure…

1.varies with trim 0.0-1.16
2. 5.0
3. 4.47
4. 4.41
5. Varies with gate trim pot. .06-5.69
6 0.0
7. Varies with trim .13-5.66
8. Varies with trim .72-4.66
9 varies with trim .04-4.57
10. Varies with trim 0.0-5.7
11.8.9
12. Varies witb trim 0.0-5.7
13. 4.7
14.4.7
15. 5.3
16.varies 0.0-1.16

Im assuming those voltages shouldnt be dropping all the way down to 0.

 

[BrainDrain]

Was really hoping this was it… nope
Same thing no matter where the switches are.

Although upon further looking i think i put the switch in backwards.

The switch is technically “backwards” but as you already know will be ok as long as you remember which way is which.

If nothing else works for you try testing for continuity between points with a multimeter in this area of the schematic. It’s what I did and ended up finding the broken trace in a few minutes.

 

[Locrian99]

The switch is technically “backwards” but as you already know will be ok as long as you remember which way is which.

If nothing else works for you try testing for continuity with a multimeter between points in this area of the schematic. It’s what I did and ended up finding the broken trace in a few minutes.

View attachment 88952

Yea ive checked all those values in thay part of the circuit. Im hoping someone could give me the voltages from a working one for reference if mine are right. I dont see the 258 or 13700 voltages in any other trouble shootkng threads on it

 

[Locrian99]

The switch is technically “backwards” but as you already know will be ok as long as you remember which way is which.

If nothing else works for you try testing for continuity with a multimeter between points in this area of the schematic. It’s what I did and ended up finding the broken trace in a few minutes.

View attachment 88952

Yea ive checked all those values in thay part of the circuit.

Audio probe shows modulated signal showing up until pin 5 (where the gate comes in) of the 13700. And then its dependent on the position of the trim so I feel like it has to be in that area up there. Just cant figure out what it is.

 

[BrainDrain]

Yea ive checked all those values in thay part of the circuit.

Audio probe shows modulated signal showing up until pin 5 (where the gate comes in) of the 13700. And then its dependent on the position of the trim so I feel like it has to be in that area up there. Just cant figure out what it is.

If nothing else works I’d try checking for continuity between points that are supposed to be connected in the circled area. Idk if it’s really the right way to diagnose it but it worked for me once already when I had no idea what the issue was. It’s frustrating as heck when you know you did everything right and it ends up being a manufacturing defect. Lolll.

 

[Locrian99]

Well i do believe this did come down to switch operator error in the end.