Slambox making ticking sound when engaged

[guitarify]

So I etched my first PCB, a Madbean SlamBox. Came out great.
But after building it, all I get is a constant ticking sound. Bypass works.
I wired the power backwards originally, so I may have blown something. Though it has a protection diode, I only had a 5V instead of 9V so it may not have done it's job.
I replaced the transistor, and tried flipping it as well. Checked the soldering for bridges and cold joints.

Next I was going to start checking voltages and try an audio probe, but I was wondering if the ticking was a dead giveaway to some obvious problem. Or at least a clue to where to start checking.
Thanks for any help.

[bean]

I'd replace the diode, and maybe the electrolytic cap. You might want to socket that transistor while you are at it.

[guitarify]

I always socket the transistor, and I always forget to put it in the first time I plug everything in.

[bean]

By the diode, I meant the Zener. Are you testing it wired into a box, or just the board, BTW?

[guitarify]

I assumed you meant the zener since it was what was supposed to protect the circuit.
I'm testing it in the box. I know, I've read the advice to build a little breadboard testing circuit to test your board before wiring on all the jacks and switches...maybe next time I'll follow that advice
Haven't had time to do further testing yet as I went to see Gang of Four last night. Holy crap that was amazingly good!

[guitarify]

OK I'm still trying to figure this out. I replaced the zener and the 2 electrolytic caps, but I still get nothing but a ticking sound. I plugged in a battery and started taking voltage readings when I noticed some smoke coming from the board, couldn't tell where.

I've already gone over the joints and checked for bridging several times now. One thing I'm wondering is if I wired the 3DPT wrong. I'm assuming that in this diagram the lugs are horizontal but is that a wrong assumption. I understand the normal bypass wiring I've seen described on this site and others, but I can't figure out how this one is supposed to work. And shouldn't there be a ground coming off the input sleeve?

[bean]

Actually, check and make sure you have your DC jack wired correctly. That illustration uses an older DC jack drawing that wasn't very good on my part. You need to make sure you have the 9v/ground wired using this:


My illustration is a little misleading with the labeling of ring, sleeve and tip considering most adaptor types are negative type. The wiring diagrams for more recent projects have been changed, but I have not had time to fix up all the old ones.

The bypass wiring looks more complicated than it is, really. The two benefits of it are that the effect input is grounded when bypassed and the ground will be maintained if there is a mechanical failure with the switch.

You don't have to ground the sleeves of both jacks if you are using metal ones. If your jacks are plastic enclosed like the Marshall type, then it is a good idea to ground both.

[guitarify]

Well, I've had the DC jack wired both ways now with no luck. I actually have a Boss style jack, so when I looked at it closely it was obvious which terminal was the center negative pin.
Here's where I am now

[G]

Is there any chance you've swapped the input and ground wires at the board end?

If you have, the input cap charging and discharging could be causing the ticking noise.  And grounding your signal when you switch the pedal on.


Not that I have personal experience of having done this myself, of course.  More than once.  Oh no.

[guitarify]

Input and ground wires look right.

When I heard the ticking i was also thinking that a capacitor might do that. That's what prompted me to ask here hoping could give me some ideas of something to look for.
Got to figure out what's causing the smoke first so I can leave it powered long enough to start really troubleshooting. Though when I figure that out it may be fixed....hopefully.

[waltk]

The "smoke" issue makes me think of power getting shorted to ground somewhere it shouldn't.  I know you checked for solder bridges, but looking at your photo, it looks like the pads for R5 and R6 are very close (right under the S in Slambox).  Can't tell you how many times my etchings of a tight layout have left two pads in contact. 

[guitarify]

I scraped the board again anywhere there was the remotest possibility of a bridge and must of got something. Now when engaged there is no ticking, and some signal gets through, but its kind of farty and weak. And there still seemed to be some kind of short as the battery heats up pretty quick.
So I pulled it out of the case to isolate things better. Haven't gotten further then that cause I've had lots of work this week. But since I'm a freelancer, lot's of work=lots of money(relatively speaking).

[waltk]

Now when engaged there is no ticking, and some signal gets through, but its kind of farty and weak.

I would call that progress.  Now that you are some signal through, you should be able to follow it with an audio probe and narrow down the problem.  You know about audio probes, right? (very useful tool).

[guitarify]

Audio Probes - yes, that was my plan, but wanted to de-box it first to take all that wiring out of the equation. I'm thinking at this point it may be just a damaged component from being shorted.

[waltk]

I'm thinking at this point it may be just a damaged component from being shorted.

Yep.  Could be.  Once you let the smoke out of a component, you usually can't get it back in.  I think de-boxing is a good idea to remove potential wiring problems from consideration.  Sorry I can't offer anything useful about which component might have been fried...

[guitarify]

SUCCESS!!!
Once I unboxed, I decided to first check for something shorting to ground as my battery was still heating up quickly. So I set my DMM for continuity and put one probe on ground and started poking around. Found a trace that was shorting that had an electrolytic cap and a diode on it. So I pulled the cap and it still shorted. Pulled the diode and it basically crumpled as I pulled it out. And there was a tell-tale burn mark on the board under it. So I think I know where that magic smoke had come from.
I think what happened was I put a totally wrong diode in that spot. It's D1, which calls for a 1N4001. I now know that these are the black diodes. I had one of the tiny glass, brown and orange ones, like the zener in D2.

[waltk]

I think what happened was I put a totally wrong diode in that spot

Congratulations.  Nice detective work.  You have the patience and persistence to become a successful pedal builder.

One word of warning, the D1 resistor on that board is there to prevent damage if the power supplied mistakenly has reverse polarity.  So under normal operation, it would never be conducting.  Even a small-signal diode, like a 1n914, or 1n4148 should have worked.  I would say the two most likely causes of the problem are 1) the diode was put in backwards, or 2) a mis-wiring was feeding power with reversed polarity.  Before you hook it up again, be sure that your wiring/switching is applying the correct polarity to the board.

If the diode failure mode was an open circuit, chances are that something else on the board was fried.  If the diode failed in a short circuit condition (was it still emitting smoke the last time you applied power?), then it might have sacrificed itself, and saved the rest of your board.

Good luck...

Edit:
On re-reading your post...

Found a trace that was shorting

Are you sure the trace was shorting?  It hard to see how a shorted trace could reverse the polarity to the diode.

[guitarify]

If you read my first post it says I DID wire the power backwards originally. For some reason I was thinking the center of the power jack was positive.
I haven't re-boxed it yet, but it worked outside with an audioprobe once I replaced that diode. It seems that the diode, once it fried, was just a straight conductor to ground.

[waltk]

If you read my first post it says I DID wire the power backwards originally. For some reason I was thinking the center of the power jack was positive.

Oh yeah.  I forgot.  So everything sounds good/as expected now?
Glad you got it working.