Low Tide Non-functional after re-boxing

Hey all.

So last month I had boxed up two Low Tide builds to test and make sure they were functional, which they were and both sounded great. I had tried running them parallel for a bit in a stereo signal which sounded really amazing.

I then took them back out of their respective boxes so that I could do some artwork for the enclosures, and then boxed them both back up. One of them worked just fine and is currently on its way to my buddy, but the other one refuses to come back to life.

Board pic:
So firstly I've gone through and checked continuity at all the major connections. Power is correct and passing signal, the ground is consistent throughout, footswitch to board connections are good, as are the i/o jacks. When turned off it passes signal, and the LED does not light up. I think I may have it in backwards ALTHOUGH I made that mistake before and the pedal worked normal otherwise.

When I turn any of the knobs I get a bit of static, as well as when I turn the bias trimmer. I'm wondering if maybe I somehow fried the BBD, but I have a bunch of other I could swap out to test.

If anyone has any suggestions of where else I could check out to get this one going again I'd greatly appreciate it.
 

JamieJ

Well-known member
Firstly, parallel low tides in stereo sounds incredible. I would love to hear that.

IMO, the most likely thing to have occurred is a cracked solder joint to the FS or the pots when they were removed. Try and reflow the pots and FS to see if that helps.

It doesn’t make sense to me that the build worked and now doesn’t. So I would be doubtful that the circuit is the problem. An audio probe would be super helpful to trace through the circuit to see if that’s the case or not.
 

bowanderror

Member
Try trimming the leads on your jacks & LED, they may be shorting out on the back of the enclosure when you box it. You may also want to insulate the unused leads on your jacks with heat shrink or electrical tape. In tight-fitting builds, I will sometime cover the rear enclosure cover with electrical tape to prevent anything shorting out on it.
 

music6000

Well-known member
Hey all.

So last month I had boxed up two Low Tide builds to test and make sure they were functional, which they were and both sounded great. I had tried running them parallel for a bit in a stereo signal which sounded really amazing.

I then took them back out of their respective boxes so that I could do some artwork for the enclosures, and then boxed them both back up. One of them worked just fine and is currently on its way to my buddy, but the other one refuses to come back to life.

Board pic:
So firstly I've gone through and checked continuity at all the major connections. Power is correct and passing signal, the ground is consistent throughout, footswitch to board connections are good, as are the i/o jacks. When turned off it passes signal, and the LED does not light up. I think I may have it in backwards ALTHOUGH I made that mistake before and the pedal worked normal otherwise.

When I turn any of the knobs I get a bit of static, as well as when I turn the bias trimmer. I'm wondering if maybe I somehow fried the BBD, but I have a bunch of other I could swap out to test.

If anyone has any suggestions of where else I could check out to get this one going again I'd greatly appreciate it.
1. I have to ask, Do you have insulators between the Potentiometers & PCB, not bloody Insulation tape!
2. Test Ribbon for Continuity between Footswitch solder pads & PCB Solder pads, they are known to snap internally & as they are all held together they look fine!!!
 
Firstly, parallel low tides in stereo sounds incredible. I would love to hear that.

IMO, the most likely thing to have occurred is a cracked solder joint to the FS or the pots when they were removed. Try and reflow the pots and FS to see if that helps.

It doesn’t make sense to me that the build worked and now doesn’t. So I would be doubtful that the circuit is the problem. An audio probe would be super helpful to trace through the circuit to see if that’s the case or not.
Stereo:

Tried reflowing all the main connection points and nada. Also confirmed that the BBD isn't the issue, popped it into my Julia build and it works fine. I also also flipped the LED around and STILL nothing :(
 
1. I have to ask, Do you have insulators between the Potentiometers & PCB, not bloody Insulation tape!
2. Test Ribbon for Continuity between Footswitch solder pads & PCB Solder pads, they are known to snap internally & as they are all held together they look fine!!!
1. All the pots have dust caps except the dual gang one, but my other build worked just fine so I don't think thats it.
2. Tested continuity between the footswitch pads and the connection points on the main PCB and everything seems connected where its supposed to be and not connected also where it's supposed to be. No change in functions from the description in my first comment.
 

JamieJ

Well-known member
I would get the audio probe out next to see if you can track down any issues with the circuit.
 

music6000

Well-known member
1. All the pots have dust caps except the dual gang one, but my other build worked just fine so I don't think thats it.
2. Tested continuity between the footswitch pads and the connection points on the main PCB and everything seems connected where its supposed to be and not connected also where it's supposed to be. No change in functions from the description in my first comment.
I would check just the same, The failure rate with the dual gang touching without proper insulation is common
When you undone it from the enclosure may have twisted it against the PCB:
Do you have the Power jack connected to the right pins???

Uninsulated Pot.jpg
 
I would check just the same, The failure rate with the dual gang touching without proper insulation is common
When you undone it from the enclosure may have twisted it against the PCB:
Do you have the Power jack connected to the right pins???

View attachment 15779
Yep, centre negative barrel positive. I think my next step tomorrow will be to strip all the main board connections and put it on the test platform for further prodding.
 
Ok so slight update. I pulled it fully from the box and put it on m test platform, still nothing. So I busted out the multimeter and started checking voltages on the ICs.

I used these threads to compare:




Now all of my measurements were around the same as what was listed in these threads if maybe a tad higher, except the LM13700. Pins 5, 7, 10, and 12 all give me the same reading of about 1.6 except it flips around and extra plus or minus 0.05.

1. 1.05
2. 5.32
3. 4.72
4. 4.78
5. 1.6 (fluctuates +/- 0.05)
6. 0
7. 1.6 (fluctuates +/- 0.05)
8. 4.65
9. 4.2
10. 1.6 (fluctuates +/- 0.05)
11. 9.05
12. 1.6 (fluctuates +/- 0.05)
13. 4.74
14. 4.74
15. 5.3
16. 1.04

ALSO, comparing the voltages of both my J201s compared to here: https://forum.pedalpcb.com/threads/low-tide-almost-working-help.8179/post-73860

I'm getting values of zero on all pins of the j201 I subbed for the 2sk208-y. I don't know if that means that it's dead or if something around it is dead.

So my next question would be is my LM13700 dead? Based on those other readings it should be maybe closer to 5v on all those pins, not the ~1.6 I'm getting now.
 

bowanderror

Member
I'm getting values of zero on all pins of the j201 I subbed for the 2sk208-y. I don't know if that means that it's dead or if something around it is dead.
Are you sure the J201 is legit and has the right pinout? Based on the SMD pinout, the through hole pinout should be:

Low Tide JFET.png

J201s have DSG pinout vs. the SDG of 2SKxxx JFETs, but you would still expect to get voltage on the pins even if the transistor is inserted incorrectly. I'd check the voltage of any resistors that have traces connected to the JFET to see where the voltage is dropping out.
 
Are you sure the J201 is legit and has the right pinout? Based on the SMD pinout, the through hole pinout should be:

View attachment 16023

J201s have DSG pinout vs. the SDG of 2SKxxx JFETs, but you would still expect to get voltage on the pins even if the transistor is inserted incorrectly. I'd check the voltage of any resistors that have traces connected to the JFET to see where the voltage is dropping out.
Huh yeah that could be it. I'm sure the j201s are legit as I've built two perfectly functioning Benson preamps from the pack I bought. That wouldn't explain the fact that it was working fine for awhile and then wasn't suddenly would it? I guess I'll pull that part and put a socket in so I can swap the pins and see where that gets me first.
 
Put the j201 in the right arrangement and no change in behaviour. Gonna go through checking values around that part tomorrow as well as around my LM13700. If anyone has other suggestions I'd love to hear them!
 

bowanderror

Member
If there is no voltage on any pins of your JFET, then that's the more worrying problem. You may want to reflow the solder on the surrounding components after you check values as that can fix a cold joint or poor connection.
 
I fixed it.


Turns out when I was swapping the LED to a different colour I used too much heat and fried the trace between leg 3 of the 2n3904 and the anode of the LED. That connection is the VCC so by severing that I cut power to basically the entire input and output section of the circuit. All I had to do was jumper those two points and it fired right up!

It's working perfectly now, gonna post about it in build reports in just a few minutes.
 

NickC

Member
sorry you gave me a doubt, in my lowtide I installed a j201 instead of the 2sk208-y as you can see in the picture, I have the first pcb layout and the pedal works. Should i swap pins to get a benefit?
Are you sure the J201 is legit and has the right pinout? Based on the SMD pinout, the through hole pinout should be:

View attachment 16023

J201s have DSG pinout vs. the SDG of 2SKxxx JFETs, but you would still expect to get voltage on the pins even if the transistor is inserted incorrectly. I'd check the voltage of any resistors that have traces connected to the JFET to see where the voltage is dropping out.
 

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If it's working fine I'd say you're probably fine leaving it the way you have it. I'd only recommend changing it if you're confident in your ability to get it out without hurting it. I will say I think the pedal sounds ~5-10% better with it in the right orientation but that's probably just in my head.
 

NickC

Member
I reversed the pins, actually the improvement is imperceptible, I recommend to those who have not done so to leave the pedal as it is without risking damage. (y)
 

bowanderror

Member
sorry you gave me a doubt, in my lowtide I installed a j201 instead of the 2sk208-y as you can see in the picture, I have the first pcb layout and the pedal works. Should i swap pins to get a benefit?

In most cases, the Source & Drain pins of a JFET are interchangeable (i.e. it's a symmetric device). There are cases where that's not ideal, but I personally haven't run in to any of them. Better safe than sorry!
 
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