Diagram for Zendrive included.

[Zenbend]

I have built this hermida Zen-drive board. Grounds on the pcb and had these voltages but very quiet 🤫 when effect on. bypassed it was working clear and crisp.
These were the readings...although since changing grounds back to the board now I have some lower numbers one side of the chip.

1 -13 volt 5 -6.5
2 -6.5 volt 6 -6.5
3 -6.5 volt 7 -6.5
4 - 6.5 volts 8 -0

Tried changing the grounding to see if It was better to add off board grounding.
Any help would be appreciated!

[Zenbend]

The readings are now.
1 -14.4 5 - 14.4
2 -3.5 6 - 2.64
3 -2.5 7 - 2.64
4 - 0.  8 - 3.68

[Marcos - Munky]

First of all, looks like you're using a 15V power supply. Use a 9V one. Also, looks like your power supply pins are reversed.

[Zenbend]

power supply pins from the jack should be reversed. (Centre is negative on my adapter). I think the readings are same on a different 9v adapter. Might be my meter. I'll try another meter. Still only sound while in bypass after switching the jack pins. All pins read 0 though.

[ElectricDruid]

Those voltages around the op-amp are way out.

A 15V power supply isn't typical, but TBH with this circuit, I don't think it should be a problem.

Pin number 1 has the full voltage on it. That's not right.
Pin 5 has the full voltage on it. That's not right either.
Pin 8 *doesn't* have the full voltage on it, and it should.

The Vref voltage isn't half the supply.

There's a lot wrong here.

I found your numbering of the op-amp pins a bit suspicious too. Did you go around anti-clockwise from the notch 1,2,3,4,5,6,7,8? Because you wrote them down as if you'd gone from the top down, left side , then right side: 1,2,3,4, then 5,6,7,8. That labels the pins 5-8 back to front.

HTH

[Zenbend]

Those  reading came out same with two different meters , same volt reading with a 9v batterie, will check this out tomorrow / I've been troubleshooting the switching area, don't understand why the voltage was different since trying grounding off the board. first posted readings were from before that was tried and put back, still reading are as stated. I wrote it as 1234 top  left side and 5678 top right down. 5678 reverse order  is correct then (anti clockwise)

[ElectricDruid]

Ok, that helps.

That means pin 8 (your "5") *does* have the full voltage, which is getting closer.

But Pin 1 is still way wrong, and the Vref bias supply is very low. Are there any shorts on the boards?

[Zenbend]

Here are the current reading. (Updated)

1 -10.8 8 -9.5
2 -6.  7 - 9.3
3 -6.  6 - 9.3
4 -0.  5 - 9.3

[Marcos - Munky]

Pins of the CI are laid out like this:
1-8
2-7
3-6
4-5

Also, post pics of yout build. It may be something very easy to fix but you didn't found out even after checking everything again and again, but another pair of eyes may be able to find it easily. This happens more often than you think, I had some builds that I spent days searching for the problem and in a minute somebody found a solder bridge or a wrong value resistor, even I checked everything a thousand times.

[Zenbend]

Using cloth covered amplier wire seems like overkill now.

I had 1.5 k resistors on hand, should I use 1k ?
The 10k resistors are 3 Watts, should I try a 1 watt ?

[Marcos - Munky]

Post a good pohoto of the solder side.

For the parts and wires: 1k5 should be no problem. For guitar pedals, 1/4W resistors are more than enough. And that wire sure is overkill, you can use thin wires because the current is low. But all of those won't make your build don't work, just make it bigger.

[duck_arse]

one of your pics shows a metal bodied DC jack. if you are using a centre negative supply, the [metal] barrel of the jack will be positive. this causes a problem when case-mounted, because the case is held at [relative] negative by the in/out jack sleeves. you need either a plastic dc jack, an insulated body metal jack, or a metal jack wired centre positive instead.

[Zenbend]

 clear picture of the solder side. Thanks kind folks!



The metal jack can be insulated with nylon washers. I hadn't thought of that. thanks for the tip.

Will be great when time comes to box this, should make a great Christmas present.

[Zenbend]

Anyone who may have a bit of troubleshooting experience maybe can help!

Thanks in advance

[Rob Strand]

I am really struggling to follow the voltages because I don't know how you are numbering the pins.  Marcos-Munky has the same problem I'm sure.
The pins are numbered like this when you look from the top (the top is the side with the IC markings).
Can you repost your measurements with the correct numbers.  It will help everyone *a lot*.


The second problem is the voltages keep changing and it doesn't seem like you are changing the circuit.  This is bad but it is also a hint.   The voltages might be changing because of your pot settings.

You need to take two sets of voltage measurements:  one with gain/drive pot fully counter-clockwise and the other with the gain/drive pot fully clockwise.

What you should see is the voltage on pins 1,2,5,6,7 are all the same as the voltage on pin 3.   If that is not true then next you should confirm that at least the voltages on pins 5, 6, 7 are all the same, also, make sure these voltage don't change when you adjust the treble pot.
=====================
These kind of look like you have to right numbering.
It doesn't look right that pin 1 can be higher than the power pin, pin 8!

1 -10.8     8 -9.5
2 -6.         7 - 9.3
3 -6.         6 - 9.3
4 -0.         5 - 9.3

So you might want to adjust the drive/gain pot to see if the voltage on pin 1 changes.
There's something wrong around the drive pot.  The fact pin 2 and 3 are in agreement
but pin 1 is off might mean you have a short between pins 2 and 3.

[Zenbend]

Thanks for the orientation. I had changed that as I saw this noted earlier.
Here's another try with changing  pots resistance reading: with volume control up all the way first. tone control doesn't effect any of the readings but pin 8 was sort of jumping around between 0.7-5.8 while the gain knob doesn't effect any of the pin readings I've taken.

1 -11. 8 -0.7-5.8
2 7.3  7 -3.7
3 -7.3 6 - 3.7
4 -0.  5 -1.1

(Turning volume control down)very  similar the post a few posts back.

1-10.8 -5.8
2-6.7 7-2.3
3- 6.7 6-4.3
4-0. 5 -0

[duck_arse]

Zenbend - for the life of me, I can't find a board to match yours anywhere. can you point us/me to the source of your board, and perhaps a circuit diagram to match your build, please?

[Rob Strand]

I can't make a lot of sense out of your measurements because they are not consistent.
When you measure the voltages where are you connecting the negative lead (black)  of the meter?
I mean the exact point eg. on the input socket, or on the PCB, or on the chip.

There may be a problem with how you have wired the grounds or the sockets. With the battery disconnected you could check that all points connected to ground are actually connected; sockets, PCB, pots.  The fact the Volume control has an effect means there's something seriously wrong as this pot should have no effect.  Beyond that you may have solder bridge so you need to check over the whole board by eye.  It could also be an etching problem on the PCB which is shorting stuff out.

In order to bypass the socket issue I suggest you temporarily connect the battery wires directly to the PCB
and re-take the measurements.

[bluebunny]

I'm still not convinced you're counting the pins correctly.  Particularly this:

but pin 8 was sort of jumping around between 0.7-5.8

Pin 8 is power.  It should be the same as your battery or power supply (around 9V).  But it's way lower than your alleged pin 1??  As Rob says, please tell us exactly how and where you are taking your readings.  Perhaps an annotated picture of the top of the board (zoom in on the IC) with your readings would help too?  The only reading that's in a happy place is pin 4 - ground (0V).

(Puzzled bunny...)

[Rob Strand]

The only reading that's in a happy place is pin 4 - ground (0V).

Good point.   I noticed that as well when I was trying to decipher the pins but I didn't consider it in my last post. I kind of implies the grounds are connected correctly. 

So how is the Volume control affecting the voltages!