# Issue with Low Tide Mod build



## pcborpcp (Feb 13, 2022)

Hi there,

I got the Low Tide Modulator pcb along with some other projects. While I could finish the other effects just fine, I came across a problem with the Low Tide. I hope you can help me.

So the issue at hand is that the polarity protection diode (D3) gets fried whenever I power up the circuit.
After the first time, I removed all IC’s and transistors, because the board got really hot. But even without transistors and IC’s connected, the D3 gets fried immediately. I even tried to use a N4001 diode instead of the BAT48. The diode remains to get fried and it gets really hot. 

I switched out the DC socket, double and triple checked the polarity of the wiring and the DC plug (center negative) and it’s all correct. I even let a friend look over the build, just to make sure I didn’t miss anything. 

Do you have any idea, what the problem might be?
I would really appreciate your support on this.

Thanks


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## carlinb17 (Feb 13, 2022)

How are you powering it and can you post pictures?


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## pcborpcp (Feb 13, 2022)

carlinb17 said:


> How are you powering it and can you post pictures?


I'm powering it with a universal AC/DC power supply with 1500mA. It works fine with my other pedals. I can take some pictures, but I have to remove the pots first.


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## zgrav (Feb 13, 2022)

sounds like a possible short to ground but this is all theoretical.  post detailed pictures of both sides of the board and you may get better feedback.


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## pcborpcp (Feb 13, 2022)

zgrav said:


> sounds like a possible short to ground but this is all theoretical.  post detailed pictures of both sides of the board and you may get better feedback.


Alright, here are some pictures - I hope they're detailed enough.
You will notice the damaged soldering spots for C32, 39, 40, 41. But this happened after the issue occurred. I thought one of the caps might be faulty when the diode got fried, because I forgot to measure them before, so I desoldered them. But I was unable to get the solder to flow again and had to push a needle through the holes to get the caps back in. I know this might be an issue (I measured continuity and it still seems to work though), but it was not the cause of the problem.


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## zgrav (Feb 13, 2022)

are you having the same issue with the board in and out of the enclosure when you are testing it?


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## pcborpcp (Feb 13, 2022)

I didn't put it in an enclosure yet.


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## zgrav (Feb 13, 2022)

FYI  --  those jacks might be a problem for you when you put everything in the enclosure.

use your dmm and see what the resistance is between the positive power supply wire and ground (no power applied to board).


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## pcborpcp (Feb 13, 2022)

zgrav said:


> FYI  --  those jacks might be a problem for you when you put everything in the enclosure.
> 
> use your dmm and see what the resistance is between the positive power supply wire and ground (no power applied to board).


Thanks, yeah I know. I have to order those slim fit jacks. These are just for testing purpose.

So the DMM reads 08.50 mOhm. Does this help?


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## zgrav (Feb 13, 2022)

the next thing I would suggest is cleaning off your board with Isopropyl alcohol on the solder side.   and then post another detailed picture.  I understand that you had the problem before you pulled out the parts that look messy on the board, but those places look problematic now.  I think you are going to need to use the schematic to make sure the mounting holes for those parts are still connected to the parts shown in the schematic.  doing that may also isolate the other issue you are having.   other folks may have suggestions too on things to check.


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## zgrav (Feb 13, 2022)

I am sure you realize by now that the low tide is a tricky build where the kind of troubleshooting you were doing can spiral out of control and create more problems than it solves.


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## pcborpcp (Feb 13, 2022)

zgrav said:


> the next thing I would suggest is cleaning off your board with Isopropyl alcohol on the solder side.   and then post another detailed picture.  I understand that you had the problem before you pulled out the parts that look messy on the board, but those places look problematic now.  I think you are going to need to use the schematic to make sure the mounting holes for those parts are still connected to the parts shown in the schematic.  doing that may also isolate the other issue you are having.   other folks may have suggestions too on things to check.


Thanks for your help. Believe me, I'm very aware that I've complicated the problem with the pulled caps. I'm very upset that I messed up those spots. I will make bridges between the problematic places and the next connection when possible. Like I said before, I checked continuity between the connections and it seems to be fine. I've attached some more pictures and hope someone else might chime in with another idea.


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## zgrav (Feb 13, 2022)

You now have the  diode D3 removed.  RIght?  What happens when you are powering the circuit now?  Anything?  If nothing is smoking or heating up, see if you are having any voltage showing up at any of the transistor or IC contacts on the board.  The point is to make sure that all of the power is reaching the board through the power diode and not through some other route.


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## pcborpcp (Feb 13, 2022)

zgrav said:


> You now have the  diode D3 removed.  RIght?  What happens when you are powering the circuit now?  Anything?  If nothing is smoking or heating up, see if you are having any voltage showing up at any of the transistor or IC contacts on the board.  The point is to make sure that all of the power is reaching the board through the power diode and not through some other route.



Yes, D3 is removed. When I power up the circuit,  I get 9.22V at the D3 negative side, but nothing anywhere else. Nothing gets hot.
But here's a head scratcher: when i put an LED with a 4k7 resistor in D3, the LED lights up and doesn't get hot. But there's also no voltage on the transistor and IC contacts.


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## zgrav (Feb 13, 2022)

The LED lighting up when in D3 suggests that there is some kind of connection to ground.  Which would also explain why there is no voltage showing up in the transistors and ICs.


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## pcborpcp (Feb 13, 2022)

zgrav said:


> The LED lighting up when in D3 suggests that there is some kind of connection to ground.  Which would also explain why there is no voltage showing up in the transistors and ICs.


Do you have any idea where that connection might be?


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## bowanderror (Feb 13, 2022)

I built the LT as well, and it's a complex build to troubleshoot, but well worth the effort. Here is the schematic, which is a critical reference during troubleshooting. Without being able to power up the unit, you'll mostly be looking to find connectivity (the beep setting on your DMM) between components that shouldn't be connected.

A potential problem area is going to be around those capacitors you mentioned:



I can't quite tell from the grainy pics, but there may be solder bridging some traces that were previously under the solder mask (the insulating black stuff that peeled off). This could be grounding a part of the circuit & causing your short.

These pictures look better, but we still can't see much of anything due to the low light. If you have a bright lamp or a well-lit area that you can take photos in, that will increase the contrast & remove the grainy noise from the images. From there we may be able to see where the problem is.


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## zgrav (Feb 13, 2022)

Use your DMM to measure the resistance between the ground pad and the side of D3 that does not connect to the power.  What do you get?

If it is no resistance or low resistance. you will need to isolate the unwanted connection to ground  The most likely cause would be a solder bridge between two connections on the board, since you seem to have had the problem before you started pulling pieces off of the board.  It is also possible though that the damage to the board from removing parts may have created a short to the ground plane in the board that might be harder to diagnose and repair.  You can do a visual inspection to see if you have any stray solder bridges between pins that are close together.


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## bowanderror (Feb 13, 2022)

zgrav said:


> Use your DMM to measure the resistance between the ground pad and the side of D3 that does not connect to the power.  What do you get?
> 
> If it is no resistance or low resistance. you will need to isolate the unwanted connection to ground  The most likely cause would be a solder bridge between two connections on the board, since you seem to have had the problem before you started pulling pieces off of the board.  It is also possible though that the damage to the board from removing parts may have created a short to the ground plane in the board that might be harder to diagnose and repair.  You can do a visual inspection to see if you have any stray solder bridges between pins that are close together.


I'd do the same at both pads of C39, 40, & 41 as that will help us identify if they are the problem. For electrolytic caps, the the square pad is the (+) side and the round pad is the (-) pad side. You should get a beep (or close to 0 ohms) on the (-) pads as they are connected to ground. On the (+) pads, you should get a resistance of less than ~2.2k ohms on C39/40, and a much higher resistance on C41 (possibly no connection).


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## pcborpcp (Feb 13, 2022)

bowanderror said:


> I can't quite tell from the grainy pics, but there may be solder bridging some traces that were previously under the solder mask (the insulating black stuff that peeled off). This could be grounding a part of the circuit & causing your short.



Yeah sorry, I'm terrible at taking photos. I tried to get a better look at those spots. Just want to reinstate that the short already appeared before I've created that mess. But I know it doesn't help.


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## pcborpcp (Feb 13, 2022)

Hi there,

I got the Low Tide Modulator pcb along with some other projects. While I could finish the other effects just fine, I came across a problem with the Low Tide. I hope you can help me.

So the issue at hand is that the polarity protection diode (D3) gets fried whenever I power up the circuit.
After the first time, I removed all IC’s and transistors, because the board got really hot. But even without transistors and IC’s connected, the D3 gets fried immediately. I even tried to use a N4001 diode instead of the BAT48. The diode remains to get fried and it gets really hot. 

I switched out the DC socket, double and triple checked the polarity of the wiring and the DC plug (center negative) and it’s all correct. I even let a friend look over the build, just to make sure I didn’t miss anything. 

Do you have any idea, what the problem might be?
I would really appreciate your support on this.

Thanks


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## pcborpcp (Feb 13, 2022)

bowanderror said:


> I'd do the same at both pads of C39, 40, & 41 as that will help us identify if they are the problem. For electrolytic caps, the the square pad is the (+) side and the round pad is the (-) pad side. You should get a beep (or close to 0 ohms) on the (-) pads as they are connected to ground. On the (+) pads, you should get a resistance of less than ~2.2k ohms on C39/40, and a much higher resistance on C41 (possibly no connection).





zgrav said:


> Use your DMM to measure the resistance between the ground pad and the side of D3 that does not connect to the power.  What do you get?
> 
> If it is no resistance or low resistance. you will need to isolate the unwanted connection to ground  The most likely cause would be a solder bridge between two connections on the board, since you seem to have had the problem before you started pulling pieces off of the board.  It is also possible though that the damage to the board from removing parts may have created a short to the ground plane in the board that might be harder to diagnose and repair.  You can do a visual inspection to see if you have any stray solder bridges between pins that are close together.


 Thanks, I'll measure everything tomorrow and will report back. Thanks for your help, I really appreciate it.


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## bowanderror (Feb 13, 2022)

pcborpcp said:


> Thanks, I'll measure everything tomorrow and will report back. Thanks for your help, I really appreciate it.


No worries man, I know your pain! Those photos are a LOT better.

The red circles are potential short circuits, and the yellow ones are solder joints that may or may not be completely soldered (may need to touch them up).



I would also go back and clip any leads that are poking out, especially the stranded wires used for offboard stuff. They may not be the problem now, but can be an issue during boxing.

Here is a color-adjusted closeup of the cap section where the mask has come off:



Most of the square (+) pads look ok, and the solder creep on the (-) pads may not be an issue as long as it's just bleeding into the ground pour. Can't quite tell if there are any traces close to C40.

For anyone else helping with troubleshooting, here is the silkscreen layer with component names:


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## bowanderror (Feb 13, 2022)

Just as a heads up, you may want to turn your soldering iron temp up a bit, that will help the solder flow more easily & give you smoother, more "domed" pad joints. There are lots of leads on the component (top) side of the board where the solder hasn't flowed through, which often means the temp was too low to fully wet the solder. If the joints look lumpy or dull (not shiny), it usually means either your tip wasn't sufficiently cleaned & carried oxidized solder onto the joint or that your iron is set too low for the type of solder/size of the pad. You can also add additional flux to help prevent cold solder joints.

It looks like the type of damage done around the capacitor pads was probably a result of pressing the tip too hard onto the pads rather than heat damage. Always try and make sure your tip is well-tinned, and that you're in contact with both the pad & the component lead. Pressing harder or twisting your tip won't help with heat transfer, so be as gentle as you can and flux/clean your tip for difficult joints.


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## pcborpcp (Feb 13, 2022)

bowanderror said:


> Just as a heads up, you may want to turn your soldering iron temp up a bit, that will help the solder flow more easily & give you smoother, more "domed" pad joints. There are lots of leads on the component (top) side of the board where the solder hasn't flowed through, which often means the temp was too low to fully wet the solder. If the joints look lumpy or dull (not shiny), it usually means either your tip wasn't sufficiently cleaned & carried oxidized solder onto the joint or that your iron is set too low for the type of solder/size of the pad. You can also add additional flux to help prevent cold solder joints.
> 
> It looks like the type of damage done around the capacitor pads was probably a result of pressing the tip too hard onto the pads rather than heat damage. Always try and make sure your tip is well-tinned, and that you're in contact with both the pad & the component lead. Pressing harder or twisting your tip won't help with heat transfer, so be as gentle as you can and flux/clean your tip for difficult joints.


Thanks! Your previous post is super helpful and detailed.

My soldering iron temp is usually 572 °F/300 °C, is that too low?

The damage around the capacitor pads happened because I desoldered them and couldn't get the solder out of the holes. I had to push a needle through the hole on one side, while applying pressure with the soldering iron to the other side, that's how it happens. i tried to use a desoldering pump and wick with flux, but the solder wouldn't come out. I usually have no problem with getting holes clean with a pump, but here I tried it for  an hour without success.


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## bowanderror (Feb 13, 2022)

pcborpcp said:


> My soldering iron temp is usually 572 °F/300 °C, is that too low?


What type of solder are you using?


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## pcborpcp (Feb 13, 2022)

bowanderror said:


> What type of solder are you using?


lead based solder with 2,5% flux.


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## bowanderror (Feb 13, 2022)

pcborpcp said:


> lead based solder with 2,5% flux.


What is the Sn/Pb percentage?


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## pcborpcp (Feb 14, 2022)

Alright,

I re-soldered the pads that bowanderror highlighted (updated photos attached)

Then I measured the connections as zgrav suggested.

I put a fresh BAT48 in D3 and measured the resistance between the ground pad and all connections. I also measured all the other electrolytic caps and thought it might  be helpful to check continuity of all connections as well. I made a chart with the data - see attachment below.


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## pcborpcp (Feb 14, 2022)

bowanderror said:


> What is the Sn/Pb percentage?


It's 60% Sn and 39% Pb.


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## Stickman393 (Feb 15, 2022)

You have a dead short between VCC and ground, judging by those measurements.

Might be a good idea to take a magnifier to the back of the board, try to find any lingering solder bridges.  They can be *super* tiny.


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## pcborpcp (Feb 15, 2022)

Stickman393 said:


> You have a dead short between VCC and ground, judging by those measurements.
> 
> Might be a good idea to take a magnifier to the back of the board, try to find any lingering solder bridges.  They can be *super* tiny.


I can't find anything. This is driving me nuts!


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## Stickman393 (Feb 15, 2022)

Check there.  You're basically looking for any spots where VCC and ground pads are in close proximity. 

If you can follow the positive trace after the BAT48 on the board, it might lead you to the culprit.

Basically, when you plug in this thing your power supply drives the maximum amount of current that it is able to deliver through this short on the circuit board.  It's no wonder that it's getting hot...

Happy hunting.


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## pcborpcp (Feb 16, 2022)

Stickman393 said:


> Check there.  You're basically looking for any spots where VCC and ground pads are in close proximity.
> 
> If you can follow the positive trace after the BAT48 on the board, it might lead you to the culprit.
> 
> ...



Thanks for chiming in on this, Stickman393.

I checked the part you highlighted, but couldn’t see anything problematic.
I then went on and measured resistance between every component and the positive DC pad. It was a bit of work, but I think I was able to isolate the problematic section. You can see it in the attached picture. Everything in the red section reads O.L. on the DMM. Every other contact has resistance (except some IC pins).

I inspected the section but couldn’t make anything out visually. My next step would be to pull out the caps C2, C3 and then C4 to check if they’re ok. But I thought I'll post this update first, to see peoples opinion on this.


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## Stickman393 (Feb 16, 2022)

O.L. on your multimeter means Over Limit.  Basically, the resistance between 9v and those points in red is too high for your meter to measure.  If your meter has a limit of say, 10 megaohms on the high end, all that means is that the resistance between those two points is more than 10 megaohms.

Given the part you've highlighted, I'd say reading over limit between those sections and 9v is no big deal.  BUT, I think that the fact that you've decided to start poking around with your meter and the schematic is GREAT.  It shows initiative and a desire to learn and understand the inner workings here: it's basically the same way I started out trying to understand a circuit.  Not that I have access to any kind of wealth of knowledge...most of us are still learning here.

The measurements that you took that concerned me were for C22, C5, C41 and C32.  Those four should read *far* more than 0 ohms to ground on one side of the component, and 0 on the other side of the component.

The reason for this is that each of these have one lead that connects to ground, while the other connects to a pad that has potential to ground (that is, voltage) once the circuit is powered.

This difference in voltage is what allows these capacitors to build and store a "charge".  If resistance on *both* sides of the component to ground is 0, that means that the capacitor will never build a charge, sure, but it also means that the resistance between two points that are supposed to have a difference in potential is zero.

Which...ah...is a problem.  Ohms law tells us that Current equals Voltage divided by Resistance, or I=V/R.  If we substitute our knowns, that equation becomes I = 9/0.

Since division by zero is impossible, I (current) must be infinite.  In reality, every material has some kind of resistance, so current won't necessarily be infinite, but it'll be A LOT.

I think I recall you saying that you were using a 1500ma 9v power supply.  So...thats probably about what your upper limit would be.  If we apply Watt's law (power=voltage x current), we can see another point of interest.

9v X 1.5A = 13.5 watts

Well...that's significantly higher than what your BAT48 is rated for.  No wonder those things are burning up!

Though now that I take a second look at your readings, I'm curious if you measured those components on both sides, or if you swapped the polarity of your leads while measuring the same pad?  If you did the latter, I'd recommend going back and measuring between ground and both pads on those four components and reporting back.  Polarity will not matter for these measurements


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## bowanderror (Feb 16, 2022)

Sn60/Pb40 solder melts around 361-370°F, so your iron may be set too high for that particular solder. That said, the soldering iron set point for a particular solder is usually higher than the melting point anyway, and is highly dependent on the power rating (in Watts) of your soldering iron and the size of the tip you're using. If you're having trouble getting the solder to fully melt at 570°F, then it's probably either a tip cleaning issue, flux issue, or the tip is shot. A setting of ~400-450°F is more reasonable for the solder you're using. What type of flux are you using?

Stickman is right that your Vcc is shorted to ground somewhere on the board. I'd remove the sockets you have for the +5V regulator and see if that solves it, you can solder that part directly to the board anyways. I know it sucks, but removing components attached to Vcc is a pretty foolproof way to find the short. Like Stickman mentioned, I'd focus on parts that have Vcc & GND pads close together, especially those that may have shorts on the top side of the board (like electrolytic caps).


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## zgrav (Feb 16, 2022)

FYI  -- easiest way to remove the 3 pin socket without damaging the board would be to cut the socket into three pieces and then remove it one pin at a time.


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## Stickman393 (Feb 16, 2022)

^ I would disagree RE: soldering iron temps there.

Soldering iron temps have a lot more to do with heat transfer than they do with the ultimate temperature of the joint.  That's because the majority of the heat applied goes towards a latent process - the non-sensible heat required to turn a solid into a liquid.

Same deal as when you boil a pot of water: the temperature of the water rises to 212⁰F at sea level, but then it starts boiling.

The temperature of the water doesn't rise beyond 212⁰, but heat is still being applied to the water.  So where does the heat go?

Behold...the latent heat of vaporization.  The heat energy causes a rapid expansion in the volume of the water molecules, at which point individual molecules break loose of the bonds of liquid water and become water vapor.  The energy applied is reflected in _molecular activity, _but not in temperature.

This hidden heat of state change is difficult to overstate: for water, you need one BTU per pound of water to raise the temperature of that pound of water by one degree F.  But to evaporate that pound of water?  That'll take a total of 970 BTUs.  It takes more than five times the amount of heat energy required to bring a pound of water from it's freezing temperature to it's boiling temperature (180 BTUs) in order actually boil the whole pound.

The latent heat of fusion for 60/40 solder is about 395 times the amount required to heat it by one degree.  Transferring that much heat efficiently requires either a large tip or a high temperature delta.

Hell, it's impossible to set my own iron any lower than 662⁰f...cause I'm using an induction iron, and the temperatures are determined by selecting a tip rather than a setting on the screen.  350⁰C is as low as they go.

But...anywho...thanks for sticking with me on all that.  I work in thermodynamics (*cough*HVAC*cough*) so I like to spread my knowledge of the super awesome world of heat transfer.

I'm a big fan of the first law of thermodynamics.  You know, the law of the conservation of energy.  That's a good one.  I'm lazy as fuck.


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## pcborpcp (Feb 17, 2022)

Stickman393 said:


> O.L. on your multimeter means Over Limit. Basically, the resistance between 9v and those points in red is too high for your meter to measure. If your meter has a limit of say, 10 megaohms on the high end, all that means is that the resistance between those two points is more than 10 megaohms.
> 
> Given the part you've highlighted, I'd say reading over limit between those sections and 9v is no big deal. BUT, I think that the fact that you've decided to start poking around with your meter and the schematic is GREAT. It shows initiative and a desire to learn and understand the inner workings here: it's basically the same way I started out trying to understand a circuit. Not that I have access to any kind of wealth of knowledge...most of us are still learning here.


Oh man, this is such a bummer. I can’t believe I went over the whole circuit for nothing. But I admire your positive spin on this embarrassing situation 



Stickman393 said:


> Though now that I take a second look at your readings, I'm curious if you measured those components on both sides, or if you swapped the polarity of your leads while measuring the same pad? If you did the latter, I'd recommend going back and measuring between ground and both pads on those four components and reporting back. Polarity will not matter for these measurements


No, I didn't swap the leads. I put the black lead on the negative DC pad and measured both/all pins of the caps with the red lead.
I just did a measurement again (just to make sure) and it still reads 0,00 Ohm on both pins (+/-) on  C22, C5, C41, C32.

Now I did what bowanderror suggested:


bowanderror said:


> I'd remove the sockets you have for the +5V regulator and see if that solves it


 
And now I get the following readings:
C22: 21 Ohm (+) / 21,8 Ohm (-)
C5:   70 Ohm (+) / 70 Ohm (-)
C41: 54,5 Ohm (+) / 63, 3 Ohm (-)
C32: 64,8 Ohm (+) / 58, 8 Ohm (-)

So it seems Stickman393 was right all along with narrowing it down to IC1/LM78L05! But I guess the resistance of the electrolytic caps is still too low?


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## Stickman393 (Feb 17, 2022)

'Atta pepper.  No need for embarassment.  Its similar to what I tell my apprentices: if you're not breaking anything, you're not learning.

Are you referencing ground or +9v on those measurements?

Measuring resistance across caps is tricky.  In actuality, a capacitor contains an insulator, and thus it's resistance is infinite.  This is why we use them as "coupling" devices: if you examine most guitar pedal schematics, you can isolate each "building block" of the circuit by using the caps in the signal path as a start and end point.

Basically...these caps are meant to block DC from passing, so that each circuit block can operate independently and predictably when power is applied.

But...caps are not simply an insulator.  They are two plates that are separated by an insulator.

These plates operate something like how a magnet would.  If a positive charge is applied to one side, it will *attract* (or induce) a negative charge on the other.  This property allows alternating current to "pass through" a capacitor.  

Alternating current is electrons and holes constantly moving forwards and backwards in opposite directions, constantly changing the force (or voltage) at which they do so, and often changing the direction in which they move.

A capacitor will store a charge across it's plates, but as the electrical pressure is released on a plate the effect is like deflating a balloon.  This constant charge and discharge cycle on one plate induces a constant charge and discharge cycle on the other plate, which gives the appearance of AC passing across the insulator of the capacitor.  Its, like, basically magic.

DC, however, is different.  Electrons travel in one direction, holes in the other.  The electrical pressure, or voltage, does not change.  Therefore, as voltage is applied across a capacitor, electrons rush into one plate, and holes rush into the other.  They (mostly) do not travel from plate to plate, because there is an insulator between the two plates.  The voltage never changes, and a capacitor only discharges when there is a reduction in applied voltage.

But remember, electrons and holes can only leave the way they came into the cap.  They do not go in one lead and leave through the other.  For the most part.

Sooo...what was the point of all that?  Ahhhh, erm, well to explain that it is that exact property that tends to confuse ohm meters.  Ohm meters operate by applying a voltage...typically around 1-2Vdc, and using the measured current between the leads to determine resistance.

Ohms law.  V/I=R.  That's all it's doing: taking two knowns: the voltage the meter applies, and the current that it measures, to determine the unknown R Variable.

BUT...you're doing this with a very low voltage that is capable of generating...eh...not a lot of current.  Because of this, when you place an ohm meter across a capacitor the meter will see electrons moving...but that current will slow as the cap in builds a charge.  Because of this, you will see the resistance measurement increase slowly over time.

If you read all that...uhhh....well, Imma level with you: part of how I learn is by restating what I've learned.  That's why a lot of my posts tend to be fuckkkin essays.  So thank you for bearing with me.

And second, if that's all gibberish, that's OK.  Like I said, nobody should listen to me.  Or at least, people should be entirely skeptical of what I have to say and I appreciate when folks pointing out when I get shit wrong.  Even if my lizard brain gets all rage and murder for a couple mins.

See?  We're all sane here.


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## fig (Feb 17, 2022)

I rather enjoyed the read. 😁


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## pcborpcp (Feb 13, 2022)

Hi there,

I got the Low Tide Modulator pcb along with some other projects. While I could finish the other effects just fine, I came across a problem with the Low Tide. I hope you can help me.

So the issue at hand is that the polarity protection diode (D3) gets fried whenever I power up the circuit.
After the first time, I removed all IC’s and transistors, because the board got really hot. But even without transistors and IC’s connected, the D3 gets fried immediately. I even tried to use a N4001 diode instead of the BAT48. The diode remains to get fried and it gets really hot. 

I switched out the DC socket, double and triple checked the polarity of the wiring and the DC plug (center negative) and it’s all correct. I even let a friend look over the build, just to make sure I didn’t miss anything. 

Do you have any idea, what the problem might be?
I would really appreciate your support on this.

Thanks


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## bowanderror (Feb 18, 2022)

Stickman393 said:


> The latent heat of fusion for 60/40 solder is about 395 times the amount required to heat it by one degree.  Transferring that much heat efficiently requires either a large tip or a high temperature delta.
> 
> Hell, it's impossible to set my own iron any lower than 662⁰f...cause I'm using an induction iron, and the temperatures are determined by selecting a tip rather than a setting on the screen.  350⁰C is as low as they go.


My mind must have been in the clouds when I was writing that, because I 100% mixed up my °C and °F... 

My iron is in Celsius and is set to 350°C (662°F), and that's for 63/37 eutectic solder (with a lower MP of 183°C/361°F). Now that I re-read pcborpcp's comment, 572°F (300°C) is DEFINITELY too low, which makes sense given the lack of thermal damage to the board. 

*pcborpcp*: I'd give 350°C/662°F a go, but feel free to bump it up/down to find a temperature that works for your given tip/solder/workpiece combo. The higher temp should make soldering & desoldering a breeze compared to what you had it set for before!


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## pcborpcp (Feb 19, 2022)

Stickman393 said:


> If you read all that...uhhh....well, Imma level with you: part of how I learn is by restating what I've learned.  That's why a lot of my posts tend to be fuckkkin essays.  So thank you for bearing with me.
> 
> And second, if that's all gibberish, that's OK.  Like I said, nobody should listen to me.  Or at least, people should be entirely skeptical of what I have to say and I appreciate when folks pointing out when I get shit wrong.  Even if my lizard brain gets all rage and murder for a couple mins.
> 
> See?  We're all sane here.


No worries, your posts are insightful and I know I have a lot to learn. Can you recommend any book or online resource?


Stickman393 said:


> See? We're all sane here.


That's good to know. I feel like troubleshooting this project was messing with my head.


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## pcborpcp (Feb 19, 2022)

bowanderror said:


> My mind must have been in the clouds when I was writing that, because I 100% mixed up my °C and °F...
> 
> My iron is in Celsius and is set to 350°C (662°F), and that's for 63/37 eutectic solder (with a lower MP of 183°C/361°F). Now that I re-read pcborpcp's comment, 572°F (300°C) is DEFINITELY too low, which makes sense given the lack of thermal damage to the board.
> 
> *pcborpcp*: I'd give 350°C/662°F a go, but feel free to bump it up/down to find a temperature that works for your given tip/solder/workpiece combo. The higher temp should make soldering & desoldering a breeze compared to what you had it set for before!


Oh yeah, that works like a charm - especially for desoldering, thank you!


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## pcborpcp (Feb 19, 2022)

So I've been looking at this thing for the last days and I think I've hit a brick wall with it. I've removed all the transistor sockets and then plugged in power to see what it's getting and my DMM reads -2.6V on the positive DC pad. Measuring the power supply shows 9V.  So yeah, unless someone has another idea, I think I'm going to shelve this project for the time being. I just don't have the skills to solve this problem. But thanks to all members who tried to help me, I appreciate it and feel like I gathered some knowledge through you.


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## Stickman393 (Feb 19, 2022)

^-2.6v to ground, with the positive lead on 9v and the negative lead to ground?

Only way I could see that being the case is if you've got your ground going to the barrel of the power jack and the center going to +9v.  But even with that, there would still likely be a short somewhere that's overloading the PSU.

It may be worthwhile to shelve it for a bit and come back when you have a little more knowledge.  I've done that a couple times.

http://www.geofex.com/ -> good reading in there.  Especially their beginners electronics article.  I read that one a while back and it unlocked a lot for me.


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## pcborpcp (Feb 20, 2022)

Stickman393 said:


> ^-2.6v to ground, with the positive lead on 9v and the negative lead to ground?


Yeah, and polarity on the power supply is center negative.



Stickman393 said:


> It may be worthwhile to shelve it for a bit and come back when you have a little more knowledge. I've done that a couple times.


I agree. I need at least some time  before I can look at it again with fresh eyes.



Stickman393 said:


> http://www.geofex.com/ -> good reading in there. Especially their beginners electronics article. I read that one a while back and it unlocked a lot for me.


Thanks! I'll dive into it.


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