Pork Barrel - effect, good; bypass, not so much...FIXED!

[Bret608]

Hi everyone,

I just finished up wiring my Pork Barrel yesterday. Unfortunately, I haven't set up a testing rig yet, so I kind of boxed it--with the full understanding that I may have to unbox if the rocking didn't work!

So, when I plugged it in, the chorus worked right away, and it sounded great except for a bit of radio or TV signal it seemed to be picking up.

However, when I switched to bypass mode, my signal was coming through, but with quite a pronounced buzz.

Where would be the first place to look? Here are the relevant facts: 1) I used a DPDT footswitch with one of LaceSensor's really cool daughterboards; 2) I noticed that I didn't have my DC jack screwed onto the enclosure as tight as it could be.

I think my true first step is to take a step back! I'm using a 1590b, so with the PCB and daughterboard, you can imagine it was tight in there! The wiring was getting me pretty frustrated. I suspect some kind of grounding issue, or even a solder bridge on the daughterboard.

Thanks to anyone who can point me in the right direction. I can always report back with pics or more information if needed.

Cheers,

Bret

[jkokura]

Pictures may help in this case Bret.

Check your voltage at the 9V input on the daughter board, 9V on the main PCB, and the ground on both. After that, start checking for continuity between your input and output wiring and ground.

Jacob

[midwayfair]

Definitely a grounding issue.

If you used plastic jacks, make sure you wired both sleeves to ground. If you used metal jacks, make sure that the same grounding point they're connected to (i.e., each other and the case) is connected to the daughter board and switch ground. Basically, make certain ALL your grounding points are connected together.

You can make an extremely simple testing rig with two jacks, a battery snap and/or power supply jack, and a few small sockets. Connect the sockets to the jacks, and then you can plug boards into the testing jacks. If you've got a small breadboard at home, just keep a pair of jacks wired together and you can plug them into the breadboard along with the circuit. You can even use one of these: http://www.taydaelectronics.com/hardware/speaker-terminals/4-way-speaker-terminal.html

[Bret608]

I appreciate the help guys!

Jacob, would I check the 9v inputs with the red test lead, and the black one touching the case somewhere? And would I use the dc voltage function on my DMM? What kind of voltages should I be seeing (9v I'm guessing)?

Is it the same procedure for checking the ground points in the PCB and daughterboard?

Thanks for the advice on the testing rig, midwayfair! And yes, the jacks do have some plastic on them. I did at least attempt to wire both sleeves to ground.

[LaceSensor]

THe daughter board has star grounding (4 ground points) which means you should be able to ground everything properly.

Post a pic.
Definitely sounds  like a grounding issue to me, but I am not really an expert.

[Bret608]

Thanks Lace...I did make use of all the ground pads on the board, which was a pleasure to solder on for what it's worth!

I'm suspecting a cold joint on the sleeve lug of the input jack--now I remember I was having a bit of trouble getting it to take solder. I'll start there and will also get into it with my DMM per Jacob's suggestion. If I can't get it resolved this weekend, I'll take some pics. I'm sure fresh eyes would help.

[Bret608]

Hi all,

Just wanted to post an update on this...I got a chance to probe around a bit this weekend (then got sidetracked, since we're in the process of buying a house and moving!). Here's a synopsis:

1) Voltages look good going into both the PCB and the Millenium Bypass daughterboard, around 8.6v in both cases. I was able to get that result using either the enclosure's screw holes or any of the circuit boards' ground points as ground--I don't know if that means anything, though.

2) My DMM doesn't have a continuity tester per se. But my "electronics mentor" told me I can use the diode tester to approximate that function. If that's true, then continuity from jack to jack through the DPDT board looks good. This is after I reflowed the joints on the jack sleeves (didn't reflow the ground points on the board just yet). I will go down to the lab this week to confirm that with one of their much better DMMs.

3) I did something potentially goofy--I ran wires from the ground lug of the DC jack to both the chorus PCB and footswitch PCB. Would that cause any trouble?

4) My DC jack is so close to the input jack due to the drilling that they're darn near touching. Not quite, but almost.

5) My wiring is not great--I noticed with the input and output jacks plugged in, the tips actually bonked into wires in a couple of places.

6) The chorus still sounds fantastic, even better after I biased it. Still getting a touch of radio noise, but I suspect that has to do with whatever bypass grounding issue I'm having.

So to sum up, I think what I need to do now is look for a bridge at the top of the footswitch PCB, particularly a ground pad bridged with the circuit input or output pad. Also, can someone familiar with Millenium Bypass confirm the transistor orientation if I'm using a 2n7000, and also let me know what kind of voltages I should be seeing there? Lace and Marauder both seem to use this bypass scheme quite a bit, so hopefully one of you can chime in! 

Believe it or not, I'm enjoying the debugging process so far! That may be because I'm at least getting a decent chorus sound and am not thoroughly jaded yet.

[LaceSensor]

If you are using the 2n7000 then you orient it 180 degrees compared to the silkscreen (which is correct for a BS170).

[Bret608]

Thanks Lace! I remember now that you told me that. Anyway, I checked and it's going the right way. Marauder is going to send me some voltage readings so I can make sure the tranny is okay.

In another thread mgwhit posted instructions on how to take both voltage and ground readings, so I went back in last night and looked at all that again. With the black DMM lead to ground (on DC jack ground lug and various other points), I was getting 0 volts with the red lead on all the ground points, both on the chorus PCB and the DPDT board. Did I do that right?

Also, and this could be a biggie, I was looking closer at the jacks when I noticed something. On the tip lug of the output jack, I had forgotten to bend the wire lead all the way around the lug before soldering. Basically, it was sticking far enough into the path of the actual jack that I bet it was bumping this stray lead when inserted. I haven't had a chance to re-test it with my guitar yet, but will ask--could that cause the problem I've described?

[Bret608]

Hi everyone,

Well, the possible fix described did not work. However, I got a chance to go into it today with a higher-quality DMM and continuity tester. Here the results:

First, I checked the voltages on each pin of 2n7000 on the Millenium Bypass switching board, with the switch on and off. All looked good except possibly the right pin, which connects to the CLR. I've asked Marauder about this as he's used this type of switching a good bit. That said, it wasn't horribly off. Here's something more-I was getting continuity between the right transistor pin and the end of the CLR that connects to it, and between the LED leg and the end of the CLR it connects to, but not across the resistor, or from the LED to the right pin of the tranny through the resistor. Would you normally see continuity from one end of a resistor to the other?

Somehow I zapped the LED in this process. I tried checking the continuity with the power on, and must have accidentally gone from the top LED pin to the +9v input or something! Not sure what killed it, but that's my theory.

Continuity was good across the in/out jacks and all points on the switching board, as well as to the main PCB. All voltages looked good at all the ground points (i.e. 0 volts). I checked voltage from the +9v input to the switching board and got 8.9v; I also got this going into the diode that came just after, but 0v at the other end of the diode.

Since I've zapped a thing or two at this point, I may just need to chalk it up to shoddy wiring and start from scratch. Let me know if there's anything I haven't thought to check.

Thanks,

Bret

[LaceSensor]

to be honest the voltages and what not wont affect the bypass at all.
Its mechanical bypass at the end of the day and should work whether you populate the LED and millenium parts.

[Bret608]

Thanks Lace--that makes sense, and I feel like things are starting to point to the power supply itself, i.e. the DC jack.

I'm thinking that because the buzz I'm getting nearly disappears when the chorus is on, meaning the power is getting the benefit of the filter caps on the board. Does that make sense? How often do folks end up with a bad DC jack? The electronics instructor who's been helping me troubleshoot suggested this yesterday.

I do still need to rule out the DC jack grounding out against the input jack. I'm thinking next step is to try and insulate those from each other with electrical tape and see what happens. If that doesn't work, time to start unboxing!

No worries either way; I've learned a hell of a lot from this process so far.

[Bret608]

Okay, now I'm getting somewhere!

This weekend, I went in with some electrical tape to insulate the DC jack from the input jack since they're so close together. Last night, I plugged the pedal in, just to see if that did anything, and if I fried anything last week besides the LED.

I was still getting the same buzzing sound in bypass, but when I looked down, I saw that the cable seemed like it wasn't plugged all the way into the output jack. When I pushed it farther in, the noise stopped and it sounded much better!

The only problem is, when I let go, it slides back out to where it started from and the noise returns. Thoughts?

I don't know if this information helps, but I used jacks that are part metal and part black plastic, kind of like what Haberdasher has in his recent Sea Urchin build report.

[gtr2]

do you have a pic of the jack?

Josh

[Bret608]

Hey Josh,

I haven't taken any pics, but that's because my family and I are in the middle of moving into a new house, and our computer is dead to boot! Usually I email myself the pics so I can post at leisure during lunch or whatever. Not an option for a little while unfortunately.

But, it may not be necessary. Yesterday, I was home in the afternoon and had a chance to experiment with different guitar cables with the pedal open. Long story short, it doesn't appear to be the jack's fault. Some of my cables looked they weren't going in all the way, and some looked fine. They all had the same noise, but the plugs were all in the right place in the jack.

Here's where I think the problem came in--my wiring on this was pretty lousy and frustrating due to the tight space. The wires from the jack sleeves to the ground points on the DPDT daughterboard are sitting right on top of the little groove just after the tip of the plug! That's why the noise was disappearing when I pushed the cable plug into the jack further--it was breaking that connection.

It's such a bird's nest I couldn't get the wires permanently out of the way without breaking another wire. I think your 3PDT wiring board could be the ticket to get me out of this jam. Then I could save the DPDT and board for my Cosmo, where I'll have more room in the 125b. I'll PM you in a bit.

Cheers,

Bret