# Abyss



## servusjon

Built the Abyss, but for some reason the yellow LED doesn't flash but lights constantly fairly weak. Also I can hear no modulation. Any ideas?


----------



## chongmagic

Have you verified that the transistors are firmly in the sockets and that they are showing a voltage? 

Have you measured the voltages on the ICs? Does the LED get brighter when you turn the intensity pot?


----------



## Robert

Make sure the pots aren't touching the back of the PCB.   

The dual pot on this one is directly behind the LED drive circuitry.


----------



## servusjon

chongmagic said:


> Have you verified that the transistors are firmly in the sockets and that they are showing a voltage?
> 
> Have you measured the voltages on the ICs? Does the LED get brighter when you turn the intensity pot?


 I haven't measured yet.

The Led doesn't respond in brightness with the pot


----------



## servusjon

Robert said:


> Make sure the pots aren't touching the back of the PCB.
> 
> The dual pot on this one is directly behind the LED drive circuitry.



No pots touching the circuit here.


----------



## Chuck D. Bones

I suggest that you touch-up your solder joints.  I see a few cold ones.  How about the Voice pot?  Does that influence LED brightness?


----------



## servusjon

Chuck D. Bones said:


> I suggest that you touch-up your solder joints.  I see a few cold ones.  How about the Voice pot?  Does that influence LED brightness?


Did that. The brightness of the led didn't change :-( 

Any ideas?


----------



## zgrav

Your yellow LED not flashing is probably just a symptom, and not the problem.  There is a part of the circuit that has a varying voltage that not only makes the LED brighter and dimmer, but controls the changes in the sounds that you want to hear in the effect.  

While having a sound play through your pedal, try shining a flashlight on the LED and photoresistors that surround it.  Move the flashlight back and forth over them and see if you hear any phasing in the sound.   If you do, it means that your problem may just be in the part of the circuit that makes the LED flash.   

If shining the flashlight back and forth over the LED and photoresistors does not change the sound you are hearing, it means you may also have problems in other parts of the circuit.


----------



## Chuck D. Bones

Try this: connect the - lead of your DVM to ground on one of the 1/4" jacks.  Set Speed & Intensity to 0.  Set Voice to 5.  Measure Vcc (pin 8 of either IC), verify it's +9V.  If that's good, measure the base & collector voltages on Q1 & Q2 and report the results.  If the oscillator is running, then Q1's collector voltage will wander around slowly.


----------



## Diatrive

I built one of these but didn't bend up the photoresistors. I have them flat. Should I bend them up?


----------



## zgrav

if you like the way it works right now you do not need to change it.   the trimmers adjust for the difference in how you place the photoresistors.  no harm in trying them the other way if you want to, especially if you can just adjust them by carefully bending them.


----------



## servusjon

zgrav said:


> Your yellow LED not flashing is probably just a symptom, and not the problem.  There is a part of the circuit that has a varying voltage that not only makes the LED brighter and dimmer, but controls the changes in the sounds that you want to hear in the effect.
> 
> While having a sound play through your pedal, try shining a flashlight on the LED and photoresistors that surround it.  Move the flashlight back and forth over them and see if you hear any phasing in the sound.   If you do, it means that your problem may just be in the part of the circuit that makes the LED flash.
> 
> If shining the flashlight back and forth over the LED and photoresistors does not change the sound you are hearing, it means you may also have problems in other parts of the circuit.



The sound reacts on the flashlight. The brighter it gets, the sound will disappear


----------



## servusjon

Diatrive said:


> I built one of these but didn't bend up the photoresistors. I have them flat. Should I bend them up?



It's bended up


----------



## servusjon

Chuck D. Bones said:


> Try this: connect the - lead of your DVM to ground on one of the 1/4" jacks.  Set Speed & Intensity to 0.  Set Voice to 5.  Measure Vcc (pin 8 of either IC), verify it's +9V.  If that's good, measure the base & collector voltages on Q1 & Q2 and report the results.  If the oscillator is running, then Q1's collector voltage will wander around slowly.



What is DVM?


----------



## servusjon

…


----------



## bergera

servusjon said:


> What is DVM?


Digital volt meter


----------



## ilgfo

Hello, new to DIY here and have the same problem as servusjon. Didn't know if should have created a new thread or not.

I have no short issues with the pots

I did some tests as mentioned above and here are my results:

Q1 Collector varies from roughly 0.54 - 3.0V - Base Voltage is 0.60V

Q2 has NO VOLTAGE anywhere

TL072 Pin 8 has voltage of 7.25V

TL074 has voltage on Pin 8 of 3.6V

I get sound and if I wave my hand over the LED area I get the warble effect but the LED is not lighting up. Obviously Q2 with no power is a problem, how do I trouble shoot this further?

Thank you


----------



## zgrav

use the circuit diagram to find the parts that connect to Q2.  use your DMM to check for continuity between those parts and the associated pins for Q2.  if you find the parts that should be connected but are not, one is either not soldered in properly or there is a break in the trace between them on the PCB.  you can figure that out after you find the specific connections on the PCB that are not properly connected.


----------



## ilgfo

Thanks zgrav, I did just that and found a total amateur mistake! I put the LED in backwards!  Overall it was a good learning experience though and taught me how to troubleshoot. I did notice when I shut the pedal off the LED still flashes. Is this normal? Thanks for your help.


----------



## zgrav

The LED should still flash when the pedal is in bypass.  You aren't really shutting it off then.


----------



## servusjon

Built the Abyss, but for some reason the yellow LED doesn't flash but lights constantly fairly weak. Also I can hear no modulation. Any ideas?


----------



## Heisenberg

Hello folks,

I'm a noob in electronics but I've built a few kits already and I'm having a similar issue to the one described above (I didn't want to open another thread as this one is fairly recent).

My problem is the following:

* The indicator LED doesn't light up when toggling the effect;
* Initially I thought only the boost stage was working, after reading this very thread I've tested flashing a torch on the photo-resistors and the effect kicked in;
I don't have a spare LED to replace the internal one right now, but considering the the external LED is also not working, I'm wondering if the problem might be somewhere else.

In the attached image, you'll notice that I've removed the internal LED already (and the 25k pot is not soldered because of that)





Thanks


----------



## Chuck D. Bones

Any chance you wired both LEDs backwards?  It's an easy mistake to make.  I know, because I did it on my last vero build.  Killed the LED too.  It's always a good idea to order spare parts, you will need them.  I suggest you check these things:
- Make sure the transistors are tight in their sockets.
- Carefully inspect all solder joints under magnification.
- Verify all components are the correct value.


----------



## Heisenberg

Chuck D. Bones said:


> Any chance you wired both LEDs backwards?  It's an easy mistake to make.  I know, because I did it on my last vero build.  Killed the LED too.  It's always a good idea to order spare parts, you will need them.  I suggest you check these things:
> - Make sure the transistors are tight in their sockets.
> - Carefully inspect all solder joints under magnification.
> - Verify all components are the correct value.



Hey Chuck, thanks for your help. I did all what you suggested, triple checked all the component's values, the transistors are firmly in place and I verified all the solder joints and redid a few that required and replaced the LEDs with new ones. Still, the exact same issue, the LED's don't light up, but if I point a flashlight to the photoresistors the effect works.

Any other suggestions?

Thanks again.


----------



## Chuck D. Bones

With INTENSITY all the way down and VOICE all the way up, you should get a pretty bright glow out of D2.  Did you read this article?  There's not much that can cause both LEDs to be off except installing them backwards.  If you have a DVM, then set the controls per the first sentence in this post and measure the voltage at each pin of Q2.  Should read something like this:
E: 4.4V (pin closest to C15)
B: 5.0V (middle pin)
C: 7.4V (pin closest to RATE pot)


----------



## Heisenberg

Chuck D. Bones said:


> With INTENSITY all the way down and VOICE all the way up, you should get a pretty bright glow out of D2.  Did you read this article?  There's not much that can cause both LEDs to be off except installing them backwards.  If you have a DVM, then set the controls per the first sentence in this post and measure the voltage at each pin of Q2.  Should read something like this:
> E: 4.4V (pin closest to C15)
> B: 5.0V (middle pin)
> C: 7.4V (pin closest to RATE pot)



Hey Chuck, thanks so much for your time and patience.

The LEDs are indeed inverted ?‍♂️ . I was following the build guide here and it shows the LEDs as the symbol #3 from the article, so when I installed following the build guide they ended up inverted as the in the PCB, the orientation follows the symbol #1 or the new standard. Thanks again, I'll re-re-reinstall them LEDs and I'll update here for future reference.

Cheers.


----------



## Chuck D. Bones

I would not reuse LEDs that have been installed backwards.  Reverse voltage damages them.  4 possible outcomes:
1.  LED is dead, no light comes out
2.  LED performance is degraded, light output is not as strong as it should be
3.  LED is "walking wounded" - it works now but may fail at any time
4.  LED functions according to spec, you dodged a bullet.

#4 is the least likely.


----------



## Heisenberg

Chuck D. Bones said:


> I would not reuse LEDs that have been installed backwards.  Reverse voltage damages them.  4 possible outcomes:
> 1.  LED is dead, no light comes out
> 2.  LED performance is degraded, light output is not as strong as it should be
> 3.  LED is "walking wounded" - it works now but may fail at any time
> 4.  LED functions according to spec, you dodged a bullet.
> 
> #4 is the least likely.



Can confirm that the LEDs orientation was the culprit. The old LEDs were working fine, it seems, but I replaced both with new ones anyway, now the pedal is working perfectly.

Again, thanks Chuck for your time and prompt help!


----------



## Chuck D. Bones

You are very welcome.  Good to hear you got it working.  Now you can play "Bridge of Sighs."


----------



## chongmagic

I tell you what I always do, after building so many pedals and getting the orientation incorrect. I always just put the LED into the holes and bend the leads so that they contact the solder pads. I will hook up the power leads to a testing board I have and see if the LED lights up. If not I either have it in backwards or something else is wrong. But in the end it saves a lot of time.


----------



## zgrav

I do the same thing with the LED orientation.  Test it to get it to light up before soldering.


----------



## chongmagic

Yeah bad experiences led me to this, I was building a tremolo and it had an internal LED that I installed backwards. Ended up ruining the board by trying to desolder the LED.


----------



## Heisenberg

Yeah, lesson learned. From now on, sockets everywhere. Even though I couldn't really find them at the local store here in NZ .


----------



## Chuck D. Bones

HA HA HA HA.  You should even socket the sockets, just to be on the safe side.

But seriously folks, I only put in sockets for parts I know I'm going to change: EEPROMs & Germanium transistors.  Sockets can cause as many problems as they avoid. Here's a way to protect the board when you're removing a part: cut the leads on the part first. Now you have better access to the solder pads and you only have to unsolder one lead at a time. The parts is destroyed, but it was probably fupped duck anyway, so no harm.  That's how the pros do it.


----------

