SOLVED Help with Low Tide schematic

C

comradehoser

Well-known member
My problem: everything about the pedal works very well and as expected (or unexpected) EXCEPT the gate pot changes nothing at all in the sound CCW or CW. Gate trimmer ditto, full CW or CCW, no change.


Checked continuity of everything from the transistor before the gate pot to the transistor after, and all is connected.

What I need help in understanding is whether I need to proceed further down the schematic to investigate what could be non-functioning in the gate control. Does the downstream bit with the LM258P and all that also affect the gate control? I am guessing so, since there is no trim anywhere else, and I'm guessing "Trim 2" refers to the Gate trim. I'm not super sure what I'm looking at, actually, in terms of understanding this big-ass complex circuit and what/how the subunits are delineated and work, particularly (and obviously) the gate control.

I am also assuming LPG refers to the Gate ("Low Pass Gate?" qu'est-ce que c'est?) so... it's important? LPG control from the LM258P and R29 connects where? To the LM13700N LPG control?
 
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Alright, well, the gate trimmer DOES do something. No signal passes until the last 25% of rotation, then goes from muffled to more trebly.

Followed calibration protocols. There is still no perceptible change to me at all between fully CCW and fully CW on the gate pot in any trimmer position. What I get at 0% is what I get at 100%.

Demos of the original pedal iirc seem to affect the signal quite a bit from very muffled to basically clear. Definitely do not have that. But I definitely have effected signal and "glitch". What is it supposed to sound like? Is it just that the lpg is too subtle for me or I'm suffering from "that's just the pedal" again?

Reflowed all points I could, tested that the pot was 100k and operational. No change.

Likely culprits?
 
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I'm just going to do the super dumb version of troubleshooting and build another board. Doing it for a friend anyway. If there's no difference, I'll know I've fallen victim to "does it just sounds like this-itis.." Yet again. If not, I will bust out the resistor code sticker and go to town.
 
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Have you checked the Fairfield Shallow Water threads on Reddit/TGP/etc ?
May be an answer to your circuit-ailments in the commercial unit's threads.
Seems there are a number of ways to mess up the pedal with the internal-trimmer settings.

Fairfield's FAQ page.

More pertinent to your problem and a possible solution to your project that could potentially permit negating a 2nd PCB purchase:
selfctrl

SOLVED Thread 'Low Tide - LPG not working.'

Hi everyone.

First post on your forum, so please be gentle. :)
I've been building for around 6-7 years, don't have a ton of actual electrical knowledge.
But I'm usually competent enough to figure things out in the end.

I've just completed my Low Tide build, all controls are behaving as expected, but alas the Low Pass Gate doesn't seem to be doing anything. I guess I'd describe it as permanently open, everything is very clear and turning the pot or adjusting the gate trim doesn't seem to be doing anything.

I've been testing voltages but honestly not 100% sure what to be looking for to...
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Perhaps there are other potential pointers to be purloined from other PPCB threads ...
 
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Feral Feline--as usual, coming through with helpfulness and enthusiasm. Grand merci.

Unfortunately, yeah, first thing I did was to hunt down the (many, many--like what's up?) shallow water threads, and went through several iterations of trim pot adjustment according to the steps in the thread and the fairfield guide. Seems like his deal was an incorrect resistor, and I am definitely not ruling that out.

But, instead of decoding 70-odd resistors, since I actually have the second board and plan on building it next, I might as well just "build-and-compare," since I just don't know tangibly what to listen for to even determine if I do have a problem. It's not very obvious to me. Einh, I dunno.

Also, my pedal otherwise is working great, lots of warbly goodness. just the main gate pot seems to do absolutely nothing to the signal regardless of trim pot position. The fact that the signal only comes through in the last 25% of the trimmer rotation, though, doesn't seem right.
 
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You're too kind, comrade — I'll agree with "enthusiasm", but my "helpfulness" is questionable. 😸

That's great you've got another board to be able to compare; I agree with Erik — decoding the resistors won't take as long as you may think, and even if it does you may come away with having memorised a few values.

I like to use Digikey's online colour-calc — for me it's faster than when I use a chart such as PPCB's sticker ( which I still use if I'm just looking up one or two resistor values).
For checking an entire PCB, the online calc gives me better accuracy because it's more methodical, entering in each colour-band for each resistor — it seems slower, but ... checking large numbers of resistors with just a chart I loose my place and make too many mistakes and then have to recheck so it's actually slower overall for me.
 
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BigBlackZero
BoysBrownOne
RaceRedTwo
OurOrangeThree
YoungYellowFour
GirlsGreenFive
ButBlueSix
VioletVioletSeven
GenerallyGoldEight
WinsWhiteNine

I still do a lot of counting zeros on my fingers for the multiplier band, and I keep the chart on the wall at the workbench, but if I’m reading troubleshooting threads and lookin for errors I can mostly get by with the Mnemonic.

I don’t build pedals often enough to keep that fresh in my brain, but luckily I read a lot of troubleshooting threads! Since Robert is kind enough to print the values on his boards, I can usually just pull up the main product image to check against. Admittedly, checking your whole Low Tide board for you would have been a bit of a chore, but I might have done it if the picture had been oriented horizontal and focused and lit a tiny bit better.

I remember thinking that mnemonic was a crazy thing to try and remember, but it turns out if you can commit zero through three to memory, that will often get you through more than half the resistors.
 
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Yeah! Thanks both of you. I definitely have the tendency of doing a lot of work because I'm lazy.

And I also read a lot of troubleshooting threads, hahaha, although lately more build reports... That's the dangerous subforum for me.

I was just thinking to myself last night, yeah I'll just read the resistors...
 
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Sooo, went over everything, and at R48, [edit: (after the gate pot, on the VCC path going into pin2 of Q3)] there was a wee little 1/8 watt format resistor that I had to break out my hand microscope to read the bands for. It read 2.4K, but it was supposed to be 620k. Multimeter reading: sure enough, 2.39k ohms.

Went to go find the bag, and wouldn't you know it, Tayda did me dirty in the pink sachet, and packed me 2.4k resistors in a bag labeled 620k.

Or, maybe I restuffed those little buddies in there by accident, but I prefer the latter scenario.

Soldered up a 560k and a 63k, measured to 619k, figured whatevs, swapped it in, and ta-daaa... sounds like I expected it would. We have lovely gating, folks, from totally muffly warbles, to warbles that poke in and out of the mix depending on pick attack, to consistently bright warbles. It just took what I thought was a pretty decent pedal to a really interesting--maybe even a great--pedal.

Thanks @Erik S and @Feral Feline for pushing me off in the right direction and providing the encouragement and wherewithal to do what I knew I'd have to do. I would have repeated the mistake without checking all the resistor values first and concluded that the pedal was bogus.

\Cheers/
 
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Lazy!?!

SAL LAZY MOON MAN good name for lazy sprocket!.webp
"If I wasn't so lazy I'd punch you in the stomach."

I'm lazy, but not as lazy as Sal, I'd never punch anyone in the stomach.

I'd aim for their face.
(JOE KING)
I'm a pacifist, albeit a passive-aggressive one.




CONGRATS! Right on! Not so lazy after all. You, I mean, not me. I'm almost as lazy as Sal.


I actually typed the following diatribe earlier but forgot to hit "post":
"I don't have everything memorised, but after a while some things stick out;
for example, if I see a yellow and purple band together I know it's going to be 47 something or 4.7 , .047 depending on the multiplier — my achilles heel.
Brown black black 1, 10. 100...
Red Red... 2.2 , 22 , 220 ...

It probably helped that my Amp-Sifu got several boxes (each about a foot-and-a-half square) FULL of random resistors from his friend's radio shop that was shutting down;
I helped organise/sort most of those, using a piece of masking-tape on the edge of the sorting table that showed the colour bands — there's still a couple boxes left to sort and every time I visit Hong Kong I try to chip away at some more sorting and he says "Don't worry about that, it's not important". Everything from tiny resistors that could be classified as SMD if you clipped the leads, right up to 2w and even 5w resistors in all manner of values including some oddball decades.
Sorting and using are different endeavours though, and it's easy to just look at two resistors to see if the colour-bands match without knowing what the colours mean.
Piles and piles...


While I prefer to work with paper, I leave schematics and build-docs on my computer, upon the laptop's lid is Robert's colour-code helper-sticker. So I can quickly flip down the lid and check a single value if I'm not embroiled in Digikey's online colour-calc."


CONGRATS once again!
 
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Yeah, since doing PTP, I'm getting pretty good at recognizing resistors, but I still don't trust myself enough to do a troubleshoot without an external reference.

I'm working lazy like I can't stand dealing with parking, so I just bike everywhere.
 
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