Build Your Own Clone Message Board

Finished building the Lil Analog Chorus together with Lil Beaver and Lil Mouse. (Beaver and Mouse are great)

The Lil Analog Chorus is not working.

LED light is active when effect engaged.
Sound is present when in bypass.
All components have been 'reflowed' and checked for correct placement.
Prior to reflow engaged pedal emitted a kind of white noise that had a modulation to it that reacted to the depth and rate controls.
Since reflow output is silent.

Performing Test with Audio Probe I have audio present in the circuit up to and including R9.
Sound is present on the input pin 3 of the MN3007.
Sound is NOT present on pins 7 or 8 of the MN3007.

Any assistance would be appreciated.

Voltage readings on MN3007
1 - 8.7
2 - 4.3
3 - 1.8
4 - 0
5 - 0
6 - 4.3
7 - 1.75
8 - 1.75

Voltage readings on CD4047
1 - 8.7
2 - 0.06
3 - 7.5
4 - 8.7
5 - 8.7
6 - 8.7
7 - 0
8 - 0
9 - 0
10 - 4.3
11 - 4.3
12 - 0
13 - 8.6
14 - 8.6

Board Images attached.




Thanks,

Here are the voltage readings for the other IC's.

Voltage readings on TL074

1 - 1.6
2 - 1.6
3 - 1.7
4 - 9.0
5 - 2.0
6 - 2.7
7 - 1.4
8 - 4.0
9 - 4.0
10 - 3.8
11 - 0
12 - 4.4
13 - 1.1
14 - 1.5

Voltage readings on LM358

1 - 1.3 -> 2.4 approximate
2 - 4
3 - 4
4 - 0
5 - 1.3 -> 3.2 approximate
6 - 2.2
7 - 0.1 -> 7.0 approximate
8 - 8.9

Update,
If I turn my amp up a LOT i can tune the VR4 pot to hear a very weak signal that sounds a little distorted.
It does not sound like the signal is being modulated.
Thanks
Adrian

Hi - welcome to the forum!

Thanks for the photos and voltage readings - makes our job a lot easier!

It looks to me that you've reversed the positions of R21 and R27. But that wouldn't cause the issues you're reporting.

From your voltage readings, it looks like the majority of issues surround the TL074. You should have 9 volts on pin 4, 0 volts on pin 11 (which are good), and about 4.5 volts everywhere else. The 4.5 volts is controlled by the trim pot, so that is variable, but pins 1-3, 5-10, and 12-14 should all be within a few tenths of a volt of each other. Your voltages range up to a difference of 2 volts. Try adjusting the trim pot so that the voltages on pins 8-9 are about 4.5 volts and see if the remaining voltages come up or are unaffected.

You should try reflowing and cleaning up your soldering again. Sometimes it takes a few shots to correct random bad joints. And you have solder blobs here and there on the bottom of the PCB that can cause issues. Those can usually be easily cleaned up with some rubbing alcohol.

Here is some guidance on reflowing your solder and solder technique:

http://www.byocelectronics.com/board/viewtopic.php?f=9&t=52211

http://www.byocelectronics.com/board/viewtopic.php?f=9&t=52188

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

Thanks Morgan,

The instructions specified to swap the 39k and 47k resistors. (page 7 - "before you begin"). I found this a little confusing, should i swap them back?

Here are the voltage readings on the TL074 after trimming VR4 to receive 4.5 volts on pin 8.
The results are not that different. For verification can you confirm that all pins except 4,11 should be around 4.5v?

Voltage readings on components
R6 (10k) 4.57v
R7 (10K) 4.57v
R8 (10K) 4.57v
C5 (10n) 4.5v in 1.11v out
C6 (560p) 4.5v in 0v out (ground)
R9 (4k7) 1.1v

new Voltage readings on TL074 - reference in ( v )

1 - 1.68
2 - 1.68
3 - 1.72
4 - 9.00 (9.0)
5 - 1.26
6 - 3.04
7 - 1.46
8 - 4.58 (4.5)
9 - 4.57 (4.5)
10 - 4.33
11 - 0.00 (0.00)
12 - 4.56
13 - 1.11
14 - 1.51

In the meantime Ill do another reflow pass.
Thanks
Adrian

Back of board pics after solder 'reflow' and clean with IPA.
Unfortunately the reflow had no change to my current output woes.

(ive annotated in the first image what looks like a solder bridge but its a bent component tail not touching anything)





Thanks, hope this helps.
Adrian

OK So i tried the "push the components" test to see if i heard any disturbances indicating a loose connection.

I found a loose connection on the TL074 (pin 3 4 or 5) and after fixing I now have full volume on output BUT no Chorus
I carefully adjusted the Variable resistor VR4 and still no chorus sound.

Performing Test with Audio Probe I still have audio present in the circuit up to and including R9. No output on pins 7 or 8 of MN3007.


Updated Voltages on TL074 with VR4 set to 4.5v on pin8.

1 - 1.71
2 - 1.70
3 - 1.78
4 - 9.00 (9.0)
5 - 4.55
6 - 4.56
7 - 4.55
8 - 4.55 (4.5)
9 - 4.56 (4.5)
10 - 4.32
11 - 0.00 (0.00)
12 - 4.55
13 - 1.33
14 - 3.55

Thanks
Adrian

Following on from the fact that I now have unaffected audio coming out
I traced the audio back from the output.

Audio is present on
R20
R19
R18
R17
But not R16

Also NO audio is present on Pins 5 and 6 on of TL074.

Does that narrow it down?
Adrian

Nice job! We're getting there.

The TL074 voltages are still not right on pins 1-3 and 13-14.

Pins 12-14 make up the input buffer to the BBD. The 1.33 volts on pin 13 is concerning as that pin is supposed to be tied to pin 14, so the the voltages on both pins should be the same. The voltages look like pin 13 is not making contact with the pcb. You need to do some work in this area: verify that pins 13 and 14 are connected together. If they are not, carefully resolder the connections. Also check out the nearby components - C5, C6, and R8. Once satisfied, probe pin 14 to see if signal is exiting the buffer circuit and entering the BBD at R9.

Next, pins 1-3 make up the output buffer for the exit of the BBD. Voltages there look like they will not pass signal. Again, those voltages look like the IC pins are not making good contact with the pcb. Pins 1 & 2 should connect together. Pin 3 should connect to one side of R13.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

thanks Morgan,
Can you let me know what voltages I should be reading on those nearby components?
My previous Voltage readings on the components were:
R6 (10k) 4.57v
R7 (10K) 4.57v
R8 (10K) 4.57v
C5 (10n) 4.5v in 1.11v out
C6 (560p) 4.5v in 0v out (ground)
R9 (4k7) 1.1v

Ill check the TL047 contact pins again tomorrow morning.
Adrain

The voltages on the passive components are dependent on the voltage coming from the chip. So we don't really use the voltages on those components to troubleshoot. What you want to do with those associated components is verify that they are the correct value and touch up their solder joints to make sure you don't have any bad connections.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

YAY,

Resoldering pins 7-14 of TL074 did the trick.

The chorus sounds gorgeous.

Many thanks for your patience Morgan.

Please change the post title to "solved"

Adrian