Hello! My Zendrive has no drive!

[Kipper4]

Gain
1 no sound
2 distorted signal
3 distorted signal

Have you a spare pot? preferably OVER 10k value?
Could you solder it. Just asking at this stage.

Have you got a Spare resistor say 50k  100k  500k?
We could test the pot without removing it by adding some parallel resistance and see if it improves the gain. (one end of R to lug1 tother end of R to lug3)


"And it's not in the area but I descovered the + end of C6 has no signal"

C6 is in the DC power supply. It's role is to smooth out the DC ripple. Not part of the audio path.
As are all the power supply componants. Not part of the audio signal path.

Briefly
Power supply.
LEDR is a current limiting resistor for the indicator led5mm
D1 is a reverse polarity protection diode. Intended to give some protection for a short time if somebody plugs the wrong power supply to the effect.
Next is the power pins for the IC 712
C6 well we know what that does now.
The two 10k resistors form a voltage divider whos output is at the junction (node) of the two. Since they are eqaul value the voltage out will be (Vr) +4v5 (half of the available +9v power supply.
C7 It performs the same function as out C6 but this time its smoothing the Vr.

 

[SirHugo]

I don't have a spare pot unfortunately but I'm sure I can canabalize something for a resistor.
I'll try it out. Dose that mean you belive the pot is dead ? Thanks for clarification of the power section!

[Kipper4]

Not sure if it's the gain pot. But it might be a quick test to rule it out.

[chromesphere]

Unlikely to be the pot Hugo.  I would still wager that the issue lies with an assembly error or solder / flux bridge.  I would check all joints and make sure there are no accidental connections.  Probably wouldn't hurt to remove the flux from between the pads as well. 

If you would like me to check any points for voltage on my Zen drive (madbean serendipity) please let me know and ill send them through.

Cheers
Paul

[SirHugo]

What is the best way to remove flux? There's a good deal on there from multiple reflows so that may be causing issues, at the very least it's unsigtly. My voltages seem solid, but i could do anouther check today and see if anything is amiss. But yeah despite a few reflows and a lot of probing I've yet to find a solution.

[thermionix]

I usually scratch it off with a steel dental probe type tool.  Then brush away the dust with an old toothbrush.  There are chemical sprays but they are quite expensive, and can dissolve finishes such as laquer.  A magnifying glass or jeweler's loupe is invaluable for inspecting boards for little bridges and whatnot.  Vero is about the worst, the gap between the tracks is tiny.

[SirHugo]

Ok cool man thanks! I'll clean it up and report back! Thankfully the PCB isn't vero.

[SirHugo]

Well I removed all excess flux and cleaned the residue and... dead pedal.
It works in bypass cleanly without noise, but when the effect is engauged it mute and the LED dose not light. I re metered to see what might be up and I've found some oddities.


IC1 (AD712)
P1 4.85
P2 4.79
p3 4.60
p4 0
p5 4.85
P6 4.85
P7 4.84
P8 9.72

Q1 (2N7000)
C 4.85
B 4.85
E 4.65

Q2 (2N7000)
C 4.75
B 4.79
E 4.79

D1 (1N4002)
A 0
K 9.72

D2 (BAT41)
A 4.79
K 4.68

D3 (1N34A)
A 4.68
K 4.65

D4 (BAT41)
A 4.85
K 4.75

C1 (470n) 0 - 4.59
C2 (100pf) 4.86 - 4.79
C3 (100n) 4.85 - 4.79
C4 (3n3) 0 - 4.84
C5 (470n) 0 - 4.85
C6 (100uf) 9.72 - 0
C7 (47uf) 4.85 - 0

R1 (470k) 4.85 - 4.85
R2 (1k) 4.78 - 4.79
R3 (1k) 4.79 - 4.79
R4 (10k) 4.84 - 4.58
R5 (1k) 0 - 0
R6 (10k) 4.85 - 9.72
R7 (10k) 4.85 - 0
RPD (1M) 0 - 0
LEDR (4k7) 9.72 - 9.72

Drive (500k A)
1 4.86
2 4.79
3 4.79

Tone (50K B)
1 4.85
2 4.85
3 4.85

Voice (10k B)
1 4.79
2 4.79
3 4.79

Volume
1 0
2 0
3 0

LED (5mm) 9.72 - 0

Power
Tip 9.72
Ground 0

So yeah clearly no good having 9.72 on the LED and both sides of the LEDR. And other connections have lost a bit of current.

[Kipper4]

All Dc voltages look good.
Where does the probe say the signal stops?
Go back to reply 28 my a.c. signal path and tell us where it stops

[SirHugo]

I'll scope it out once I'm home, I was concerned by the meter reads because the LED  had  changed  from reading 1.80 - 0 to 9.82 - 0 and the  LEDR was 1.80 - 9.72 and now 9.72 - 9.72.

[vigilante397]

I have a working Zendrive that I just finished (my own layout but using the schematic from Aion's build doc) so I can get some voltages when I get home today so you have something to compare to.

[SirHugo]

Yeah thanks man that would be absolutely be helpful!

[SirHugo]

Input (quiet)
In on switch (quiet)
In on board (loud and noisy)
C1 (both loud and noisy)
R4 (both very quiet and a little crunchy)
Tone (all three lugs quiet)
C4 (no sound and quiet and crunchy on the other side)
IC
Pin 1 (quiet and crunchy)
Pin 2 (loud but very static and crunchy)
Pin 3 (loud distorted)
Pin 5 (quiet and crunchy)
Pin 6 (quiet clean)
Pin 7 (quiet clean)
C5 (medium and clean)
Volume (lug 1 no sound/Lug 2 & 3 medium, clean)
Out on board (medium, clean)
Out on switch (no sound
Out on jack (Loud, distorted

Lol of course now the pins on the IC are working correctly

[vigilante397]

Well, I have some bad news. Your voltages look great Aside from RLED of course.

Have you tried pulling the switch out and connecting the board straight to the jacks? Whenever I'm debugging I like to remove any and all variables and go from there.

[SirHugo]

Well that's good to hear thanks for checking, and no I haven't yet but I'll try that once I'm home, do the audio probe reads reveal any clues to anyone? As I said the IC is finally working correctly albeit quiet in places, but there's a good deal of differences from the last time I did a probe.

[Kipper4]

Is it working right now?

Is the gain above unity?

Also did you double check the diode polarity?

I'll look at doing a demo next week so you can compare.

Rich

[SirHugo]

So it's kinda working, I took out the switch and signal is passing through but I have a lot of noise, almost helicopter-y, tons of treble but it seems to have more low end then before.
The LED is not lighting still.
With all the noise I'm not sure if I've got unity gain but it seems a little Woolier than before.
I have quad checked the diode orientation.
Thanks that would be great.
I would assume with all that noise there's a ground issue somewhere.

[SirHugo]

Here's a quickie sound sample with out the switch

https://youtu.be/dj6-kuNLbik

[Kipper4]

Does it do the noise in bypass too?
Stupid question maybe.


Edit
Just plugged mine in and If i have all the knobbys cranked I can hear a bit of oscillation.
I'd say it's rare I'd have the gain past 10 Oclock.

[SirHugo]

Well the bypass worked fairly well when the switch was attached but it's disconnected in the sound sample