First build Musikding der 45er not working

[Egidius]

This was my first attempt at building a pedal and unfortunately it didn't work at all. Here are some pictures of the build:
https://imgur.com/a/UelpSry
Schematics: https://www.musikding.de/docs/musikding/45er/45erschalt.pdf

When I first plugged it in, the dry signal got through just fine but there was a terrible buzzing and no phasing at all. Then something quite weird happened. I tried removing the wire from the 3PDT that connects the circuitboard to ground when the pedal is off. Normally that shouldn't interfere with the signal going to the board but it did. After I removed that wire, no signal got through anymore and I just hear quiet pops now. The pops do react to the potentiometer, they get faster when I turn it right.

I connected a 9V battery to circuit and measured some voltages.

Battery voltage: 9,5V

Q1
g = 0,25V
d = 0,25V
s = 0,47V

Q2
g = 0,25V
d = 0,25V
s = 0,47V

IC1
P1 = 1,48V
P2 = 1,06V
P3 = 0,87V
P4 = 0V
P5 = 0,25V
P6 = 5,00V
P7 = 8,57V
P8 = 9,33V

IC2
P1 = 8,62V
P2 = 8,58V
P3 = 0,25V
P4 = 0V
P5 = between 4,34-4,52V, oscillating slowly
P6 = between 4,75-4,95V, oscillating quite fast
P7 = between 4,50-5,11V, osillating quite fast
PB = 9,36

D1
C = 0,25V
A = 0V

I measured this with the potentiometer turned all the way to the right.

I used all the correct parts and they are all oriented correctly. I used 2N5457 transistors so they are supposed to be inserted opposite of what is drawn on the pcb. I double checked the wiring, checked for bridges, checked the connections on the pcb and all seems to be ok. I really have no idea why this isn't working. Does anyone know what might be causing this or what else I could check?

[antonis]

Hi & Welcome..

pin 3 & 5 of IC1 should stand at about 4.7V (1N5230 Zever breakdown voltage..)

Check connection between D1 Cathode and one leg of R16 while check connection for the other leg of R16 to +9V..

[Egidius]

Hey, thanks for the answer.

I checked the connection between D1-R16 and R16 to +9V. Both are fine. I also checked all other connections of the cathode of D1 and they are all fine.

What could I do to test IC1? Is it possible that the component is faulty?

[antonis]

What could I do to test IC1? Is it possible that the component is faulty?

There always is such a possibility but first verify D1 good working condition..

You have to measure between 4.5 and 5V across D1,from Cathode to Anode..
Your 250mV measurement calls for wrong (too high) R16 value or diode placed in reverse..

[ElectricDruid]

Welcome!

The bias voltage which is set by D1 is much too low, so the problems that you're seeing on IC1 aren't caused by the IC being faulty, but rather by the bias voltage being too low. That's why Antonis is getting you to look at the connections around D1. Until that voltage comes up closer to what we expect, the rest of the circuit isn't going to work properly.

One reason D1 might not work properly is if R16 isn't well connected - hence Antonis' tests for continuity between 9V and the top the R16 resistor and the bottom of R16 and the top of D1. The other possibility is if the bottom of D1 isn't properly connected to ground, but in that case, we'd expect the bias voltage to be too high rather than too low, so we can probably rule that out. Connecting the diode back-to-front is another possibility, so check for that too.

Another possibility is a short somewhere else that drags the voltage down. That could be any components that are connected to the bias voltage that also go to ground, so C7 or TR1, the trimmer. But the short doesn't have to be across a component. A bit of muck or a blob of solder on the bias voltage track that touches something else could be enough to do it, so try and trace the track around the board and check it is clear of any obstructions.

HTH,
Tom

[antonis]

P.S.
Just to rule out putting the blame on IC1, take it out of socket and take measurements..

[Rob Strand]

Could be D1 around the wrong way or even C7 around the wrong way (especially if it is a Tantalum).

[Egidius]

Thanks to everyone for all the suggestions. I checked both R16 and D1. They both tested ok and I redid the soldering. Both D1 and C7 are definitely oriented correctly. It seems there is some kind of short in C7. The multimeter starts beeping when I touch the pins although there is still some resistance. The three pins of the trimmer also seem to be connected to eachother. So I guess I'll replace C7 and see if that helps, although that will be something for tomorrow.

[antonis]

You can simply desolder C17 and take a measurement..

[Rob Strand]

The multimeter starts beeping when I touch the pins although there is still some resistance. T

It can be normal for the meter to beep when doing a continuity check across the cap.   The beep is the meter charging the cap.

When testing in-circuit the circuit often discharges the cap when you removed the meter.  So you will get a beep every time you put the probes on.

When testing out of circuit you might only get one beep as the cap charges up the first time and when you removed the meter it stays charged then when you put the meter on again it might not beep.

The 0.25V problem points to some load (or short) between the zener and ground.

What about your trimpot TR1.  Are you sure it's 250k  if its 250 ohm you could see 0.25V!

[duck_arse]

I seem to recall that we recently had a kit, from musikding, with a way-off value trimpot, wrecking a build. might have even been a phase45. have a very very close look at the markings on the trimmer, report them here. and measure the resistance across the two outer lugs.

edit : actually, don't bother. I had a close look, and the trimpot is marked "250" from what I can see. pull it out, and complain to the supplier.

[Egidius]

Oh damn, you are right! I checked all resistor values but forgot to check the trimmer. Definitely a rookie mistake that I will not make again.

I'll complain to the seller and see if it works when I get the correct one.

Thanks everyone for the help!