Meathead debug, please help before I throw it out the window!

[sickman82]

Hi guys, new to the forum and to the whole world of DIY pedals really. Go easy! I've done a few pedals so far, Green Big Muff, TS808, COT50, Woolly Mammoth, Fuzz Factory.

I've got some issues with my lastest build though.

I've built a DAM Meathead clone from this vero layout - http://3.bp.blogspot.com/_y7gcfRKQFgA/T ... 710238.png

I followed the layout exactly, using audio axial caps etc.

This is the wiring diagram I am using for it - http://www.madbeanpedals.com/tutorials/downloads/StandardWiring_MBP.pdf

No component substitutes have been made and both transistor pinouts are correct, polarity for capacitors are correct as well.

The problem is that I get no sound whatsoever, no bypass and no sound when engaged. I am using Switchcraft style stereo switching sockets, with 5 lugs.. the common ring, tip and sleeve plus a switch on ring and a switch on sleeve. Here's the link to those - http://www.doctortweek.co.uk/shop/article_36/Jack-Socket-1_4%22-Stereo%2C-Switched---Enclosed.html?shop_param=cid%3D50%26aid%3D36%26

And a diagram showing the lugs of the sockets - http://www.flickr.com/photos/doctortweek/4971424532/in/photostream

Q1 - 2N3904
E=8.74
B=9.10
C=9.10

Q2 - BC182L
B=9.10
C=9.21
E=8.73

The voltage on the single electro cap = +8.8     -8.72

I have tested for continuity, all grounds, wires on switch and input/outputs are passing signal.. no cold solder joints, no bridges on veroboard etc. I think it must be how I have wired the socket, or something.. hope you guys can help. Here are some pics.

Top down view of guts...




Top of board...




Bottom of board...




Input socket... (please note that one of the 3 wires going to the sleeve in this pic have been corrected, one of the 3 wires in the pic is the board ground, that is now connected to lug 2 of the switch as per the wiring diagram above)




Finally the output socket.. tip is connected to ring to make the socket mono




Apologies about the wires being the same colour, it makes it hard to distinguish what is what but I like the look.. I didn't anticipate it going wrong and having to post pictures!

Many thanks in advance..  

[frequencycentral]

Looks like your output socket ground is only connected to lug 1 of the pot. They both need a connection to the board ground. ie all grounds connect together.

[sickman82]

So if I just send a ground to lug 3 or 6 of the switch from the sleeve of the output, would that do it?

[frequencycentral]

Yeah, try it. There might be other errors though. If your sockets were mounted to the enclosure you'd have decent grounding as the enclosure conducts, though I prefer to rely on wiring everything to everything else rather rely on the enclosure. First thing I do in any build is to wire ground to the DC socket, input, output and 3pdt.

[Govmnt_Lacky]

Looks like your output socket ground is only connected to lug 1 of the pot. They both need a connection to the board ground. ie all grounds connect together.

+1  

Personally... I HATE those enclosed jacks that you are using there. TOO MANY chances to screw up the wiring!  

It does look like you have a grounding issue as Rick has explained.

ALSO: Why do you have the TIP and RING wired together on the output jack?? That could be another reason you are not getting an output. It DOES NOT make it mono... it makes it SHORTED to GROUND.

Good Luck  

[frequencycentral]

ALSO: Why do you have the TIP and RING wired together on the output jack?? That could be another reason you are not getting an output.

Well spotted. You need to connect ring and sleeve to make it mono.

[sickman82]

I'll try that then.. tomorrow though, I've run out of fuel for tonight.

Yep, I also hate those sockets... well, I do now anyway. The tip is wired to the ring to turn the stereo socket in to a mono socket.

I'm gonna try those suggestions out in the morning.. then start looking elsewhere for my sockets! Where I order from in the UK, Dr Tweek, he only sells the enclosed type sockets and I get everything else from him.. so it just makes it easier to buy sockets from him too.. but I think in future I'll be getting them elsewhere!

Cheers guys, I'll let you know how I get on.

[sickman82]

ALSO: Why do you have the TIP and RING wired together on the output jack?? That could be another reason you are not getting an output.

Well spotted. You need to connect ring and sleeve to make it mono.

Ahh.. take a look at this ---> http://www.doctortweek.co.uk/shop/article_71/Jack-Socket-1_4%22-Stereo%2C-Switched---Semi-Open.html?shop_param=cid%3D50%26aid%3D71%26

That may be the answer to my problems right there!

[frequencycentral]

The tip is wired to the ring to turn the stereo socket in to a mono socket.

Incorrect:

It DOES NOT make it mono... it makes it SHORTED to GROUND.

You need to connect ring and sleeve to make it mono.

Doctor Tweek made an incorrect diagnosis:

Made mono by connecting tip and ring.

[sickman82]

Right, got it wired correctly this morning and now I get a bypass signal.. but no effect when engaged.. I'm gonna have a dig around the internet and see what I can find with regard to debugging this new issue but if you guys have any thoughts or tips please let me know. Thanks.

[sickman82]

Update....

Checked voltages on the transistors and here's what I found:

Q1 - 2N3904
E=0
B=1.87
C=2.42

Q2 - BC182L
B=2.42
C=1.74
E=1.72

for the electrolytic capacitors.. (I just realised there are two)

47uf
+ = 9.26
- = 0

10uf
+ = 1.72
- = 0

When I'm probing the electrolytic caps, I'm keeping the black lead of my dmm on the signal ground and probing with the red on both + and - sides of the caps. When I put the black lead to the positive of the DC jack and probe I get -9.25 on the - leads of both caps. Not sure if I am meant to do that, but I did anyway and that's what I found.

[sickman82]

Ok, audio probe time! Hope I've got the right cap size for it.

[Greenhill]

Q2 voltages seem odd. Check biasing resistors?