Loophole Issue

[andronikus7]

Hi everyone,

the Loophole is the first Mad Bean project that I have tried to build. But I have already made a few other easy effect pedals from strip board before. Unfortunately my Loophole does not function as it is supposed to. My issue is very similar to the one described by bigrigg here:
http://www.madbeanpedals.com/forum/index.php?topic=4428
Green LED is always on and cannot be switched off. No recording is possible.
But I have checked the diodes D1 and D2 already aswell as REG1. Those do not seem to cause the issue. After double checking the wiring and the soldering points I am now running out of ideas. So, I will post pictures of my PCB and my measuring values (in Volts) below. It would be very cool, if you guys could help me out.

IC1
1: 4,2
2: 4,2
3: 4,2
4: 0
5: 3,9
6: 4,2
7: 4,2
8: 8,3

IC2
1: 4,1
2: 4,1
3: 4,1
4: 0
5: 3,9
6: 4,1
7: 4,1
8: 8,3

IC3
1: 0
2: 0
3: 0
4: 4,9
5: 0
6: 0
7: 0
8: 0
9: 4,9
10: 4,9
11: 0
12: 0
13: 0
14: 0
15: 0
16: 5,0
17: 0
18: 0
19: 0
20: 0
21: 0
22: 0
23: 0,6
24: 0,1
25: 5,0
26: 0
27: 4,9
28: 5,0

IC4
1: 4,9
2: 5,0
3: 0
4: 5,0
5: 0
6: 0
7: 0
8: 0,1
9: 0,1
10: 4,0
11: 0
12: 4,9
13: 4,9
14: 5,0

REG1
In: 8,1
Ground: 0
Out: 5,0





Thanks in advance,
Nils (from Germany)

[alanp]

I'd go through it with your multimeter set to ohms and check for bridges where there shouldn't be (one probe on one net, another probe on the net next to it, and if resistance is zero when it shouldn't be, you have a bridge.)

[andronikus7]

Thank you for your help. I have checked the pcb for bridges three times now but was not able to find any. I have also checked the switches: they work properly. And none of the wires is broken. So, I suppose it might be one of the components on the pcb. Is that possible?

[jimilee]

Thank you for your help. I have checked the pcb for bridges three times now but was not able to find any. I have also checked the switches: they work properly. And none of the wires is broken. So, I suppose it might be one of the components on the pcb. Is that possible?

Very, did you check it against the layout to make sure all those solder places that are touching are supposed to be touching, or did you just eyeball it?

[andronikus7]

No, I have really worked through all the solder places on the pcb with my multimeter. There are no unwanted bridges. But I have found something else now: Three legs of the socket for IC3 are broken (pins 11, 12, 14). I had to bend them, because the guy who made the pcb for me made it a bit too small. Will repair that as soon as possible and post the results here.

[madbean]

Yeah, report back and I'll offer any thoughts if I have them.

[andronikus7]

Okay, yesterday I fixed the contact at pin 14 (and left pins 11 and 12 as they were because they are not used as far as I can see). But, still the green LED is on all the time and cannot be switched off. Rats. What else can I try?

[alanp]

What diodes are you using in D1 and D2? Should be 1n914's, I don't recognise the blue ones you have in place.

[andronikus7]

Those are 1N4148s. My dealer told me they exactly had the same specifications as 1n914s.