Eternity (Burst) build: No output

[adbernal]

Hello everyone,

My first time working with Vero, so my problem may be due to me not using Vero properly? I decided to tryout the Eternity layout by |v|ark from the Tagboardeffects blog. I get bypassed signal but once the effect is thrown in I get no signal. This is my 5th build so I'm still a beginner but I haven't ran into this problem like this. I tested with a switch and got bypassed signal. No mods to the original layout (however as you will read on I made 2 slight changes in my debugging process) which is reported as verified. Tried using different Opamps (Jrc4558, LM833, TL072) and have checked the pinout. I've gone through the layout for hours--would love to know if you can spot an error with my builds layout... I haven't been able to. Same goes for cold solder joints and bridges.

Here's the voltages on the IC: i just can't explain it.
1. +0.8
2. +0.8
3. +4
4.0
5. +0.8
6. +1.4
7. +1.4
8. +9

Tracing the voltage from the power supply: before the voltage divider with the two 10k resistors, everything that needs the full 9v gets it (pin 8, power filter cap). I do get 9v/2 at the voltage divider, but then once it passes through the 220n capacitor it drops to 0.8. I swapped the 1M resistor to a 100k to get the 4v on pin 3 (please let me know if I shouldn't do this). I also bypassed the 390R resistor to get 9v to the filter cap and pin 8 (again, please let me know if this isnt the right way of doing it). The 220n cap I actually swapped out thinking it may be defective but the new one still gets that 4.5v to 0.8 volt drop.

[adbernal]

[11-90-an]

Welcome to the forum...

Swapping the 1M to 100k can affect... something? (Impedance, loading, biasing? Not so sure..)

What was the pin3 voltage BEFORE you swapped the 1M resistor?

A capacitor BLOCKS dc voltage, so when you say it didn't pass through the cap, it actually means that there isn't a problem there...

The 390 ohm resistor serves as some sort of isolation and provides filtering along with the 47uF capacitor...

Maybe try reflowing your solder joints...

If I may ask, why do you have 3 extra lines of vero at the bottom...?



(P.s. am I the only one who cracked up when I saw the word "burst"? )

[adbernal]

11-90-an,

I really appreciate your reply and for the information. Capacitors block dc voltage... mind blown—I had never read or realized that. I was getting around 2.5v at pin3, so I replaced with the 100k. I mean, with Ohm's law V= IR and typically resistance and voltage are constants but I was thinking that for some reason current is constant and therefore voltage will drop with a drop in resistance. But I have no solid evidence to back this up lol. This is my first go round with Opamps

I'll put the 390R back in and see if I can maintain the 9v to pin8. I will go ahead and reflow all solder joints and get back to you.

From the schematics that I've seen for the eternity burst, this layout by |v|ark appears to be correct to me. I'm really interested to find out what the error is with this build. It's probably something stupid 

[idy]

The 1M resistor connects the bias to pin 3. If you measure at the viltage divider of two 10k, you see 4.5, but if you measure at the other end you will see less because your meter loads that node more; the 10k/10k is a low impedence source and less loaded by the (10M?) input impedence of the meter. Which is enough to load the 1M node by about...10%, turning 4.5 into 4v at pin 3. After a few opamp circuits you learn to expect your meter to slightly lower the bias voltage...usually by just that amount

But that bias should be bringing pins 1 and 2 of the opamp up to the same value. It isn't, so I would check for shorts/errors/ cold joints around those two points.

Just because a solder joint looks ok doesn't mean it isn't loose inside. I have done this over and over especially (don't know why) with biasing opamps.

Try checking adjacent rows of the stripboard for continuity=shorts.

[jfrabat]

In my experience, no signal typically (not always, but very often!) means a short.  I would start with the MM in continuity mode and make sure there are no shorts.  From the pics, I cant tell, but there might be a bridge between the 3rd and 4th row in the first pic right below the two break points (where you drilled).

Do you have an audio probe?  If you do, start tracing the signal and see where it dies.  If not, this may be a good time to make yourself one.

[moid]

It looks to me that there may be a number of solder bridges - I've painted areas to check in red on the image below - try running a sharp knife down the gaps between the copper strips to make sure there aren't any slight bridges:

[adbernal]

Hi guys,

Thank you so much for your guidance! So here's an update. I have reflowed every contact and ran (angrily ) a fresh xacto across every separation between strips. I made an audio probe and probed both At input and as a short to output (signal, probe, pedal, output & signal, pedal, probe, output). The problem is once the signal has to go through legs 1 or 2 of the ic I get no signal.

Even though there is some voltage present, is it still grounded? Where's the short? ARRGGGHHH!!!

[idy]

Are the voltages on pins 1,2 and 3 close to mid point? (pins 1 and 2 should mot be loaded bu the meter, they should read 4.5. Pin 3 might read closer to 4. Pins 5,6,7 should also be around that mid voltage.)

[adbernal]

Hi idy

They are not  . Pins 1&2 are reading 0.8v +/- 0.05v. Pin 3 is reading at midpoint with loading, and pins 5&6 are reading low too around 1v. Pin 4 is 0v, Pin 8 is +9v.

[jfrabat]

I overlayed your board with the guide in Photoshop thinking maybe you misplaced a component or something.  Looks like you missed a break, but it should not affect the board in any way.



But on the flip side, looks like you missed the 390R resistor and just used a link there.  Also, I did not check all resistor values, but one of your 1M seems to be wrong (the one on the left) - looks like 100K (yellow band instead of green) instead of 1M.  The 1K and the other 1M seem OK (the small ones are too small for my eyes to figure out the color correctly, so those are up to you to check!).



Can't really tell from this angle if the caps are in the right line, but in the first pic they seem to be. 

[11-90-an]

I overlayed your board with the guide in Photoshop thinking maybe you misplaced a component or something.  Looks like you missed a break, but it should not affect the board in any way.



But on the flip side, looks like you missed the 390R resistor and just used a link there.  Also, I did not check all resistor values, but one of your 1M seems to be wrong (the one on the left) - looks like 100K (yellow band instead of green) instead of 1M.  The 1K and the other 1M seem OK (the small ones are too small for my eyes to figure out the color correctly, so those are up to you to check!).



Can't really tell from this angle if the caps are in the right line, but in the first pic they seem to be. 

I knew it! I was also wondering why a “100k”resistor was there... but i didn’t really check that much so I just guessed... well nothing, actually...

And this is why i use 4-band carbon film resistors... easier on my eyes...