Spatialist - Distorted Sound

[joshuabrent]

Longtime lurker, first time poster—LED comes on, sound comes through on bypass, when pedal is engaged the signal is distorted with audible attempts at reverberation. Program switch engages variations of modulated distortion. Attaching photos of build—things to note, placed switch on the wrong side, and had to remove and insert new one on correct side, C7 cap. is socketed because i didn't have the correct value and wanted to test with a slightly higher cap, currently have the correct value in (15p.) Have yet to probe it as my experience with probing is very limited. Any help would be appreciated.

 

[owlexifry]

Longtime lurker, first time poster—LED comes on, sound comes through on bypass, when pedal is engaged the signal is distorted with audible attempts at reverberation. Program switch engages variations of modulated distortion. Attaching photos of build—things to note, placed switch on the wrong side, and had to remove and insert new one on correct side, C7 cap. is socketed because i didn't have the correct value and wanted to test with a slightly higher cap, currently have the correct value in (15p.) Have yet to probe it as my experience with probing is very limited. Any help would be appreciated.

1) ensure the backs of the pots are not touching the back of the board. these should be insulated from each other. plastic pot seal covers exist for this:

Dust Seal Cover For Potentiometer

Tayda Electronics - Get It Fast - Same Day Shipping

www.taydaelectronics.com

2)
try the pedal engaged with zero wet/100% dry mix (mix knob turned all the way down) - how is it? should be a clean pristine signal.

3)
if you have a multimeter, measure voltages at each pin of the active components - particularly the TL074, and 3.3V regulator (L78L33) - i would recommend trimming the legs shorter on that thing too.
(post the voltages here in a list)

 

[Nostradoomus]

check pins 6 and 8 of the FV-1 too, should be 3.3v

also make sure the regulator is seated well in that socket, those are meant for header pins and are much looser feeling with a transistor in them

 

[Robert]

If your 3.3V supply is good and you have a clean signal with the Mix control turned all the way down:

Connect a jumper wire between this point and ground then see if the distortion is still present in the wet signal.

 

[joshuabrent]

Thanks for the responses.

I can confirm that I get a clean signal with mix all the way down.

Will post multimeter readings tomorrow, headed into work.

Thanks again.

 

[joshuabrent]

Checking back in w/ readings for all ICs; jumper wire between highlighted point on 10k resistor did not resolve distortion in wet signal.


IC1 *TL074CN subbed for TL074

1 4.35
2 4.36
3 4.36
4 8.74
5 4.01
6 4.36
7 4.36
8 4.36
9 4.36
10 4.32
11 0.7
12 4.36
13 4.36
14 4.37

IC 2 24LC32A

1 0
2 0
3 0
4 0
5 4.3
6 4.3
7 0
8 4.3

IC3 FV1

1 2.259
2 2.269
3 2.269
4 0
5 0
6 4.50
7 0
8 4.53
9 2.11
10 1.84
11 0
12 0
13 0
14 4.50
15 4.5
16 4.56
17 0
18 0
19 0
20 1.36
21 2.0
22 1.6
23 4.4
24 0
25 0
26 0
27 2.24
28 2.23

IC 6 L78L33

1 4.53
2 0
3 8.74

Thanks for all the responses.

 

[Robert]

Your 3.3V supply is too high. Are you sure that's an L78L33 and not an L78L05 by any chance?

I'd replace that before powering it up again.

 

[joshuabrent]

Seemed probable, but the 3.3v supply used is the L78L33, to be more specific L78L33ABZ-AP.

 

[Robert]

Make absolutely sure neither of the two lower pots are touching the back of the PCB, bend them away slightly if you have to, then replace the L78L33 and measure again.

 

[joshuabrent]

put protectors on back of pots, and installed new L78L33, no change, same readings.

Started probing, get audio on R1, C1, R22, R2 and TL074, only pin 5. No audio on C3 or C6.

 

[Feral Feline]

No audio at all on C3 or C6?

That would indicate something's screwy with Pin 7 of the TL074, and with nothing at C3 nor C6 you effectively shouldn't have ANY signal getting to the output jack.
I'd touch up the solder on pin 7, as well as both C3 and C6. If still not working...

Try replacing the TL074?

 

[Robert]

You wouldn't have a clean signal if there is no signal on C6, and you wouldn't have a distorted wet signal (unless it's just noise and in no way related to the input signal) without audio on C3.

4.5VDC is going to destroy the FV-1 IC, it's absolute maximum is 3.5VDC. That needs to be solved above all else.

 

[joshuabrent]

Understood. I agree with your assessment, but unclear how to proceed.