# 🎵One of these things is not like the other! 🎶



## Pauleo1214 (Apr 12, 2022)

Don't you love when your combo build works the first time, 75% of the time?

I am currently on a hot mess streak. My last four pcbs (of which I built successfully before) produce dry signal but no modulation.
I decided to focus on another weird build, four HAARPs in parallel. A QUAARP if you will. Except one of them doesn't produce any modulation. The PCB in question is the one on the upper left (component side up), upper right (pot side up).

So far i checked all my resistors, reflowed all my solder joints, checked that the ICs are getting proper voltage (they are), swapped the regulator and tl072's, and swapped one of the EEPROMs. No dice. Could anyone who is an eagle eye with resistor color bands see if I possibly subbed a wrong value? My next guess besides that is a broken trace.


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## Pauleo1214 (Apr 13, 2022)

@PedalPCB , is there a picture of the Rev. 02.01.20 board with component numbers? I ordered another board but would like to test points for continuity to see if this can be fixed with a splice.


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## JamieJ (Apr 14, 2022)

After all you have already checked with circuit I would look at the FV-1 next in detail. Can you send us a close picture up of the FV-1?

Have you tried audio probing yet? That should isolate the problem more closely.


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## music6000 (Apr 14, 2022)

You need a better quality picture of the dud Board!


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## Feral Feline (Apr 14, 2022)

The component-side pic won't zoom in for me, but all the other pics do. 

Need a better close-up version of the component-side.


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## Pauleo1214 (Apr 14, 2022)




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## Pauleo1214 (Apr 14, 2022)

Apologies about the poor pics,  I always struggle with getting crisp photos, especially within the size limits.


@JamieJ , I haven't tried probing yet. I wanted to know if there was a pic of the board with the component numbers instead of the values, it would make it easier to follow the schematic.


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## Oh_Discordia! (Apr 14, 2022)

check the transistor - one lead isnt in the socket


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## Pauleo1214 (Apr 14, 2022)

Lowtide said:


> check the transistor - one lead isnt in the


I accidentally pulled that out as i took the photo just now.


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## Robert (Apr 14, 2022)




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## Pauleo1214 (Apr 14, 2022)

Robert said:


> View attachment 25325


Thank you!


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## fig (Apr 14, 2022)

Can you verify R9 R10 R15?

Looks like R18,R5 & R14 as well.

Probably just my screen colors...looks like double red bands 🤷‍♂️


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## music6000 (Apr 14, 2022)

Can you verify that C4 is 1nF, it looks quite large in the photo & chipped????


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## Pauleo1214 (Apr 14, 2022)

fig said:


> View attachment 25327
> Can you verify R9 R10 R15?
> 
> Looks like R18,R5 & R14 as well.
> ...


All 10K resistors.


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## Pauleo1214 (Apr 14, 2022)

music6000 said:


> Can you verify that C4 is 1nF, it looks quite large in the photo & chipped????


Yes, it is 1nf and has a "103" denotation.

I burned it because the 100k resistor gave an odd value reading relative to the other boards and i removed/ replaced it.


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## fig (Apr 14, 2022)

Once I realized both ends looked red I figured something was up


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## fig (Apr 14, 2022)

Pauleo1214 said:


> Yes, it is 1nf and has a "103" denotation.
> 
> I burned it because the 100k resistor gave an odd value reading relative to the other boards and i removed/ replaced it.


103 is 10nF right?


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## music6000 (Apr 14, 2022)

102 =1nF


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## Pauleo1214 (Apr 14, 2022)

music6000 said:


> 102 =1nF


My bad, typo. I hit 3 instead of 2.


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## fig (Apr 14, 2022)

Maybe the crystal?


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## Pauleo1214 (Apr 12, 2022)

Don't you love when your combo build works the first time, 75% of the time?

I am currently on a hot mess streak. My last four pcbs (of which I built successfully before) produce dry signal but no modulation.
I decided to focus on another weird build, four HAARPs in parallel. A QUAARP if you will. Except one of them doesn't produce any modulation. The PCB in question is the one on the upper left (component side up), upper right (pot side up).

So far i checked all my resistors, reflowed all my solder joints, checked that the ICs are getting proper voltage (they are), swapped the regulator and tl072's, and swapped one of the EEPROMs. No dice. Could anyone who is an eagle eye with resistor color bands see if I possibly subbed a wrong value? My next guess besides that is a broken trace.


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## Pauleo1214 (Apr 14, 2022)

fig said:


> Maybe the crystal?


How do you tell that the crystal's bad? Just my luck that I have to order more if it has to be replaced.


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## fig (Apr 14, 2022)

A scope, or if your DMM has a frequency function. There may be other ways?


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## peccary (Apr 14, 2022)

Pauleo1214 said:


> How do you tell that the crystal's bad? Just my luck that I have to order more if it has to be replaced.


If you find that it's the crystal and need one drop me a line, I believe I have a few from when I did a HAARP.


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## zgrav (Apr 14, 2022)

you could swap in temporarily a crystal from one of the others to see if it brings the pedal to life.  if so, consider adding in the clock module to get another odd variation for your monster build.


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## Pauleo1214 (Apr 14, 2022)

I found I had a spare bag of the crystals and swapped one. Definitely not the crystal. Given all the values are correct, there's a severed trace somewhere. Looks like I'll be hunting it down tonight with a probe. 


zgrav said:


> you could swap in temporarily a crystal from one of the others to see if it brings the pedal to life.  if so, consider adding in the clock module to get another odd variation for your monster build.


Hmmmmm.....


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## fig (Apr 14, 2022)

Pauleo1214 said:


> I found I had a spare bag of the crystals and swapped one. Definitely not the crystal. Given all the values are correct, there's a severed trace somewhere. Looks like I'll be hunting it down tonight with a probe.
> 
> Hmmmmm.....


Bummer...sorry Paul. I'm as much help as Fig in the troubleshoo....well you get the idea.


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## music6000 (Apr 14, 2022)

Pauleo1214 said:


> I found I had a spare bag of the crystals and swapped one. Definitely not the crystal. Given all the values are correct, there's a severed trace somewhere. Looks like I'll be hunting it down tonight with a probe.
> 
> Hmmmmm.....


Do you recall removing any components from this Build?
I would look at the traces around the area you may have done ie  just like the crystal you just replaced ????


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## Pauleo1214 (Apr 14, 2022)

music6000 said:


> Do you recall removing any components from this Build?
> I would look at the traces around the area you may have done ie  just like the crystal you just replaced ????


Only other component i removed was R22. The pads and traces for both that and the crystal appear fine. I am going to have a go with a probe shortly


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## JamieJ (Apr 14, 2022)




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## music6000 (Apr 14, 2022)

Pauleo1214 said:


> Only other component i removed was R22. The pads and traces for both that and the crystal appear fine. I am going to have a go with a probe shortly


Do you have Continuity between R22 & Pin 17 on FV-1, R22 opposite pad goes to Ground.


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## Pauleo1214 (Apr 14, 2022)

music6000 said:


> Do you have Continuity between R22 & Pin 17 on FV-1, R22 opposite pad goes to Ground.


There is continuity between R22 and Pin 17.

Commencing probing.


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## Pauleo1214 (Apr 15, 2022)

Sad news, everyone. 

I am about ready to conclude that the FV-1 might be bad. I followed the schematic from the output back to the input and test continuity at every point. What that search turned up was a broken trace between R4 and R18. Both read their regular component values and not the parallel value of 6.8K. A jumper between those two points did not fix the issue. 

At this point, it will be quicker and more cost effective to populate a new board.


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## Pauleo1214 (Apr 15, 2022)

music6000 said:


> broken trace between R4 and R18.
> *NOTE:* Trace also goes to Pin 6 of IC1 & R19:
> View attachment 25352


I did not junk the board yet.  Let me give this a shot. 

The curious thing I did not issue for fear of being looked at as a noob is I did not get any continuity reading across the 22K resistor on R4. A resistance reading always showed the correct value but no continuity between the two traces of R4 itself, nor the point between R18 and R4.


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## music6000 (Apr 15, 2022)

These 4 Red Circles should all have Continuity:


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## Pauleo1214 (Apr 15, 2022)

The four points in red circles have continuity. What I found that is very curious is there is NO continuity across R4 itself. 

A continuity reading across R4 on the bad board reads 0L and gives a resistance reading of 22K. 

A continuity reading across R4 on all other boards reads 1.3L and gives a resistance reading of 6.8K (parallel with R18 at 10k). 

There is continuity between lug #2 of both the Wet and Dry pots on all boards except the bad one.

There is continuity between the left side of R4 and lug 2 of the Dry pot but no contiuity between lug 2 of the dry pot and the right side of R4. That is where my readings came to a stop. I'm baffled to what is actually occurring. 

Green line on the image indicates contiuty, red line indicates none.


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## music6000 (Apr 15, 2022)

Pauleo1214 said:


> The four points in red circles have continuity. What I found that is very curious is there is NO continuity across R4 itself.
> 
> A continuity reading across R4 on the bad board reads 0L and gives a resistance reading of 22K.
> 
> ...


There should not be Continuity across R4!!!
You should not have Continuity across lug #2 of both the Wet and Dry pots!
When I do Continuity Test with DMM, I use the function that BEEEEEEEEEEEEEEBS!
If no BEEEEEEEEEEEEEEBS!, something is Broken or I have it on the wrong pads!!!


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## Pauleo1214 (Apr 15, 2022)

I apologize if I am trying your patience. I am just trying to get an understanding of the problem of this board vs. the others  

I realize I am applying the term continuity incorrectly too. The schematic shows the output lugs of the wet and dry controls are connected by the junction of R4 and R18. 

That said, the resistance reading of those resistors gives off their normal values showing they are not in parallel.


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## music6000 (Apr 15, 2022)

Pauleo1214 said:


> I apologize if I am trying your patience. I am just trying to get an understanding of the problem of this board vs. the others
> 
> I realize I am applying the term continuity incorrectly too. The schematic shows the output lugs of the wet and dry controls are connected by the junction of R4 and R18.
> 
> ...


It's all Good, did you jumper the R4 & R18 or was it OK to begin with????


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## Pauleo1214 (Apr 15, 2022)

music6000 said:


> It's all Good, did you jumper the R4 & R18 or was it OK to begin with????


Last night i jumpered the left side of R4 the right side of right of R18 which the incorrect sides to jumper.

I was going to jumper the other sides but had to mow, pick up my car from service, run an errand, drive my car back to service because the charge piping on my intercooler uncoupled, take an uber home, get groceries, and now make dinner.

I'll solder the jumper on tonight.


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## music6000 (Apr 15, 2022)

Pauleo1214 said:


> Last night i jumpered the left side of R4 the right side of right of R18 which the incorrect sides to jumper.
> 
> I was going to jumper the other sides but had to mow, pick up my car from service, run an errand, drive my car back to service because the charge piping on my intercooler uncoupled, take an uber home, get groceries, and now make dinner.
> 
> I'll solder the jumper on tonight.


If you have the Beep function on your DMM & the 4 red circles all Beep, you don't need the jumper!


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## Pauleo1214 (Apr 12, 2022)

Don't you love when your combo build works the first time, 75% of the time?

I am currently on a hot mess streak. My last four pcbs (of which I built successfully before) produce dry signal but no modulation.
I decided to focus on another weird build, four HAARPs in parallel. A QUAARP if you will. Except one of them doesn't produce any modulation. The PCB in question is the one on the upper left (component side up), upper right (pot side up).

So far i checked all my resistors, reflowed all my solder joints, checked that the ICs are getting proper voltage (they are), swapped the regulator and tl072's, and swapped one of the EEPROMs. No dice. Could anyone who is an eagle eye with resistor color bands see if I possibly subbed a wrong value? My next guess besides that is a broken trace.


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## Pauleo1214 (Apr 15, 2022)

My DMM has a Beep function on the 200 ohm setting of resistance reading. Touch any two of the four points with the probes produces a beep.

I read article that described contiuity tests using the diode mode; any reading of 0.000V indicates true continuity between two points. Any small reading indicates current flows through but with resistance. A reading of 0L indicates no current flows through (no contiuity).  Touching any of the four points you highlighted produces the 0.000V reading.

This puts me back at square 1 with the board though.


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## music6000 (Apr 16, 2022)

music6000 said:


> If you have the Beep function on your DMM & the 4 red circles all Beep, you don't need the jumper!


Test Your FV1 Legs for Continuity:


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## Pauleo1214 (Apr 16, 2022)

music6000 said:


> Test Your FV1 Legs for Continuity:
> 
> View attachment 25380


All the points have continuity between the pins and next components but i haven't tested at the diodes yet.


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## Pauleo1214 (Apr 16, 2022)

Confirmed continuity from the FV-1 to the diodes. At this point, it just has to be the FV-1 being faulty. I re-flowed the legs on it twice with no change . I have a replacement board coming Monday.  Thanks for your help!


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