Hello everybody,
Because of the pandemic my employer puts me on hold until better days so I've got plenty of times and decided to try to get back at building pedals.
I've been succesful with a Tractor Beam and a Decimator clone (really effective noise gate btw).
So, following that path, I was confident in trying a Pork Barrel 2015 rev.1 that was sitting in my drawer next to a couple of MN3007 and MN3101 that I've traded with a fellow madbeanforum user some years ago.
Everything went well while soldering, but once I fired it up : fail !
I can hear a tiny change of sound when I engage the effect, like the Depth is kind of working, but oscillations are very weak and almost inaudible, it's almost a dry signal.
The LFO Led is blinking so I'm guessing the LFO is working though.
I've double check my soldering and resolder some joint, but still the same.
So I've made some measures and notice that Pin 6 on clock is way off, so is collector on Q5 (and maybe emitter on Q3)
If you guys have some time, could you please point me in the right direction to debug this one ?
Thx
IC1 : 4558
----------
1 | 4,72
2 | 4,72
3 | 4,72
4 | 0
5 | 4,72
6 | 4,72
7 | 4,72
8 | 9,1
IC2 : MN3007
-------------
1 | 9
2 | 4,64
3 | 3,9
4 | 0,6
5 | 0
6 | 4,6
7 | 3,73
8 | 3,73
IC3 : MN3101
-------------
1 | 8,98
2 | 4,6
3 | 0
4 | 4,68
5 | varies
6 | 8,05*
7 | varies
8 | 0,6
IC4 : TL062
-----------
1 | varies
2 | 4,56
3 | varies
4 | 0
5 | 4,55
6 | 4,57
7 | varies
8 | 9,1
Q1 : 2N5088
-----------
E | 3,55
B | 4,05
C | 9,1
Q2 : 2N5088
-----------
E | 3,96
B | 4,51
C | 9,1
Q3 : 2N5088
-----------
E | 3,72*
B | 4,2
C | 9,1
Q4 : 2N5088
-----------
E | varies
B | varies
C | 9
Q5 : 2N5088
-----------
E | 0
B | varies
C | 7,7*
here are some pics of the PCB
(https://i.ibb.co/DrVTYBv/2021-01-29-11-54-18.jpg) (https://ibb.co/0sDvK06)
(https://i.ibb.co/Dp46pxy/2021-01-29-11-54-24.jpg) (https://ibb.co/vY1rY7G)
Have you tried adjusting the bias trimmer! 3.9v looks a little low. Also, the 3007 marginally works at 9 volts, Regulated 12 volts supply is much better.
Also, take a look at forum posts because I know there has been some corrections for some of the boards for this project
Thank you for your suggestions danfrank.
I've tried to bias the pedal, but as I didn't hear any effects I left the trimmer in his middle position.
I've tried with a regulated 12v power supply and still no chorus, just a weak effect, even when biasing.
At first I thought that it was one of the 2015 pcb that had to have some corrections as you mention, but mine it's the rev. 1 that has been already corrected.
Hello again,
So, here is what I've tried so far :
- replace Q5 with another 2n5088 -> still no variable voltage on Collector pin.
- replace all the transistors with 2n3904 (suspecting out of specs 2n5088 from cheap chinese seller) : same 7V on Q5 collector pin
- check if there wasn't an inversion between R41 and R37 : they are at the right place.
- check R38 : correct.
- Test MN3101 et MN3007 in another working Pork Barrel (an ooold one from 2011) : working fine
- Check voltage without MN3101 suspecting a faulty socket : 0v on Pin 6 so socket seems to be fine.
- resolder every joint that I found a little off.
Well, still not working...
What do you think can cause Pin 6 of clock and collector pin of Q5 to have fixed voltages ?
Thank again.
I've swap
Have you tried reflowing your solder joints? After some 9 years, I still have to do it on occasion. We all do.
Edit: stupid auto correct.
Sent from my iPhone using Tapatalk
Thx for the advice, but the one that is working is the oldest, this is the youngest that ain't working ! (My grand father could have said this ;D)