SOLVED Panspermeria No Effect Sound When Turned On

[leadfoot]

I just wrapped up soldering a Panspermeria Fuzz PCB. When I plugged it in, I received very splattery inconsistent effect that didn't seem to pick up the playing of the guitar. So, I rechecked all my wiring, my soldering, etc. and that all looked fine. I then looked over the build document and saw that the PCB has an extra 10k resistor on the left hand side that the build document does not have. I desoldered that 10k resistor and went from having some sound to no sound when the effect is turned on.

I've verified:
1. power comes to the effect when turned on
2. 3dpt switch is operating as expected
3. all components are soldered correctly
4. all components are the correct values

I've attached an image of the pcb before I removed the 10k resistor in the lower left-hand side of the board and after. Is there something obvious I am missing? I had looked at the other Panspermeria Fuzz threads here before posting.

Thanks in advance for the help.

 

[BuddytheReow]

What voltages are you getting on all your ICs?

 

[leadfoot]

Steady state:
Pin 6 on IC (LM386N-4): 8.31V
(assumming left to right ordering of transistors and checking collector voltages (pin 3)
Q1c: 8.26V
Q2c: 1.48V
Q3c: 0.0v (could be wrong, couldn't get a good read on it)

 

[Nostradoomus]

measure each pin of ICs and transistors (which did you use?) and report back, also a picture of the back would be good. You also have 2 current limiting resistors (main pcb and breakout) that arent necessary.

 

[leadfoot]

I have attached a shot of the back of the pcb in the first post.

As far as the CLRs, I don't mind modifying the breakout board to remove and jump the CLR and LED there since I use the LED in the main board.

Transistors are all 2N5088.

Voltages for IC @ steady state, sustain at 0, vol ~50%

Pin	Voltage	Pin Desc.
1	1.297V	Gain
2	-0.005V	- input
3	0.094V	+ input
4	0V	Gnd
5	3.729V	Vout
6	8.3V	Vs
7	4.16V	Bypass
8	1.298V	Gain

 

[BuddytheReow]

Steady state:
Pin 6 on IC (LM386N-4): 8.31V
(assumming left to right ordering of transistors and checking collector voltages (pin 3)
Q1c: 8.26V
Q2c: 1.48V
Q3c: 0.0v (could be wrong, couldn't get a good read on it)

Q2 and Q3 voltages are off, especially Q3. This would explain no signal since there isn't any voltage to turn it on!

 

[leadfoot]

Q2 and Q3 voltages are off, especially Q3. This would explain no signal since there isn't any voltage to turn it on!

Yup and the resistor I removed (which looks to be R1) based on a previous post that I probably misread is connected to pin 1 of the B100K pot essentially removing sustain control from the circuit.

 

[BuddytheReow]

I'd put that 10k resistor back in there and retest voltages.

Or put in a socket in case you want to pull it out again

 

[mybud]

There’s a post from our esteemed constituent @Robert that mentions this:

Post in thread 'Panspermia.. anyone build one of these? Sustain control issue'

Jul 25, 2021

Try jumping a 10K resistor across these two points and see if it sounds more like you expected.

• Robert

 

[leadfoot]

I'd put that 10k resistor back in there and retest voltages.

Or put in a socket in case you want to pull it out again

Added 10k resistor back in and it works. How sensitive is the circuit to guitar volume? Based on my playing (Les Paul and Stratocaster) the volume needs to be ~7 or higher at the guitar to really get anything out of the circuit -- below that its just the occasional snap crackle and pop.

 

[BuddytheReow]

I've breadboarded this circuit and it's kind of a one trick pony if you've got hotter pickups. Looking at your OP pics you may need to clean the board with some isopropyl alcohol and touch up some solder joints.

Can you provide updated voltage readings?

 

[leadfoot]

I've breadboarded this circuit and it's kind of a one trick pony if you've got hotter pickups. Looking at your OP pics you may need to clean the board with some isopropyl alcohol and touch up some solder joints.

Can you provide updated voltage readings?

My pick ups aren't too hot just standard Burstbuckers in the LP and some Klein Epic '54s in the strat.

I'll be cleaning and touching up once the effect is up and running well. It's the joy of working on it after the family is in bed.

Pin (LM386N-4)	Voltage
1	1.298V
2	0.006V
3	0.007V
4	0V
5	3.895V
6	8.15V
7	4.081V
8	1.291V

Transistor (2N5088)	Collector Voltage
1	0.656V
2	1.456V
3	0.975V

 

[leadfoot]

I referenced @debrad's build here and desoldered the extra 10k resistor from the board. I also cleaned up the flux off the board and tested again. At high volume levels on the guitar (e.g. volume at 7 or higher) the pedal works as expected, at lower volume levels the signal just disappears and no audio is heard until I raise the volume back up on the guitar.

The only thing I can think of is the diodes before the lm386n-4 ic or Q1 not biasing correctly to get enough gain on the emitter.

Any ideas?

 

[BuddytheReow]

You'll need to build an audio probe to find out where in the circuit it is dying out. They're super simple to make. If you need guidance where to test in the circuit let us know.

TUTORIAL Thread 'Troubleshooting 101'

Oct 25, 2021

There comes a time for every builder to spend multiple hours soldering, wiring, and breadboarding a certain circuit just to have it work incorrectly, if at all. This could happen on your first build or any build after that. This write up is to help you in your quest to figure out why it isn't working on your PCB, perfboard, stripboard, or breadboard and to provide some helpful tips when asking the community here. There is some great advice scattered throughout this forum and I thought it would be a great idea to compile my thoughts here

Items you will need to help troubleshoot in no...

• BuddytheReow
• Replies: 3
• Forum: The Test Kitchen

• 
• 

 

[BuddytheReow]

If I were you I'd check these points here. Just my 2 cents.

 

[debrad]

There is another note in an earlier post on this pedal (Panspermia) that may help with the volume issue:

Fourth, there is a 22k resistor soldered onto the volume pot itself (not on the pcb) between lugs 1&2, which makes it parallel to the 1M that is also between lug 1&2, meaning it's more like 21.5k, which could be why the taper is off on the volume pot (this is also mentioned but never gets added).

 

[leadfoot]

I went through the signal path with an oscilloscope and confirmed there was signal at all places. I rechecked all the solder joints and had them checked by someone much more skilled than me in soldering and confirmed they were ok.

The sustain potentiometer is very interactive with the volume knob on the guitar; which I suppose is to be expected as it's the first real component after the capacitor in the signal path.