Teddy Rupture

[StephanCOH]

Hi there. I just finished a built of the Teddy Rupture, but it does not work.

Bypass is fine, but after I activate it it first went dead silent and the LED lit up. I then reflow some solder joints, but now the LED looks like it is firing up for a microsecond and then dies.

The funny thing is, if I touch the ground tongues of the jacks with the tips of the cables, the fuzz works (do not know about the LED), but the wallwart is getting pretty hot (the pedal feels quite warm too.

Are there any points I can the measure the DC? Any help is appreciated.

Cheers.

 

[zgrav]

because your power transformer is getting warm when it is plugged in, I suggest not leaving it plugged into your effect for more time than it takes to test whatever you need to test. it is obviously under stress from something wrong in your effect, and may stop working without any warning and then you will need to replace it.

Without plugging in your effect, first check and make sure your positive and negative wires from your power jack are connected to the right pads on your PCB, and make sure that your positive wire is not shorted to ground --- there are some power jacks that have the outside of the plug connect to the case and you cannot use these for an effect pedal. then plug in your effect and use your multimeter to make sure you have the positive and negative wires correctly soldered to the power jack. then unplug it again unless you have already found and fixed some problem.

since you were getting some sound on the ground side of the circuit, with the effect pedal unplugged, use your digital multimeter to check your connection from the audio "in" and "out" pads on the circuit board to your ground connections. since you were hearing the fuzzed tone, it is more likely the short will be in the "out" side of the circuit. if either the "IN" side or the "OUT" side connects to ground, use your circuit diagram in the build document for your effect to look at the parts that are close to the input or output part of the circuit (depending on which one had the connection to ground). look for solder on the lead from a part, or the tip of a wire connected to the circuit board that is touching something else on the ground trace that it shouldn't be. if you find any of those, fix them.

if that does not help you find and fix the problem, double check all of your part values on the circuit board, make sure any ICs or transistors are oriented the right way.

 

[StephanCOH]

There must have been a short. I put the pedal to the power-adaptor I use for my pedalboard on stage. It has a status LED that lights up when it is on. I plugged in the pedal and when I hit the switch the LED of the power-supply got dimmer.

So I just took the pedal apart (boxed it before testing, which I usually do not do this way ) and it looks like the positive pin of the LED touched the sag-pot on the backside of the pcb. So I cut those wires and deinstalled the LED.

There is still no tone coming through but the wall wart does not get hot anymore. I measured the 9v+ inside the pedal and there is nothing coming through. Maybe the wall wart died and I‘ll do another test with the power supply from my stage board tomorrow.

 

[zgrav]

sounds like you're on the right track. insulate the back of your SAG pot before reinstalling the LED. : ^ )

 

[StephanCOH]

Checked with the big power supply before work this morning and got a nice 9v at the jack and at the board, so it seems like the DC is fine.

I used the 3PDT breakout-board, so tonight I'll try to connect the in and out directly to the jacks to rule out any mistakes of the switch.

The LED is still disconnected from the board. That is no problem, right?

 

[Robert]

Nah, the LED isn't required for it to work properly.

Try disconnecting Lug 1 of the Sag pot (square pad) and connect a 2K2 resistor in series with the lug and the pad.

 

[StephanCOH]

Will do that tonight, thanks.

 

[StephanCOH]

Ok, I deinstalled the 3PDT and connected the in and out straight to the board. No signal. Sag lug1 shows about 6V, the right leg of Q2 too. Volume and Gain gave no reading.

Luckily I ordered two boards, so I just did a second, barebone built with only in- and output and 9V connected to the board. I added the 2K2 for the Sag too and ... it works like a charm. It already rips and roars and even though it is not boxed yet, there is not too much noise.

So tomorrow night I'll add the footswitch. I am still not sure if I should keep the 2K2 or remove it. During my quick testdrive the Sag pot did not made so much difference (a little bit duller on the one side and a little bit more velcro-fuzz on the other side). So what do you think? Keep it or remove it?

 

[Robert]

Leave the 2K2, it prevents the fuzz circuit from pulling too much current at the lowest sag setting.

 

[StephanCOH]

Ok, cool. Thanks for the help.

Going to post some photos and a little description of the pedal in "Build reports".

 

[zgrav]

you are in a good position now to find the problem with the first assembled board, by comparing the measurements you get from the different points in each board.

of course your interest in getting the first board working is probably much less now....

 

[StephanCOH]

Hahahaha, indeed, it is ?

However, I bought the second board to build it for a buddy of mine, so I am probably going to give it try after I finished number one.
I am afraid I fried something when it shorted because of the LED.

BTW: is there a smart and easy way to get the pots off the board again? I tried to desolder the Sag pot of board one but it is still connected to the board pretty firmly.

 

[zgrav]

first do what you can to remove as much solder as possible from the pot using copper wick or a "solder sucker. then try to use your soldering tip to warm up 2 of the 3 posts of the pot and wiggle them a bit to move them out from the board. then warm up the opposite post and middle post and try to wiggle them out a bit. you will need to do that several times to free the pot.

 

[StephanCOH]

Sounds good. I tried something similar, but maybe I was just too impatient.
I'll give that a try.

 

[Robert]

I remove pots a little differently, but it takes a little practice to get it down.

Rather than remove the solder from the lugs, I actually add more to each one.... Get a nice little blob on each lug.

Now I lay the iron across all three lugs at the same time and heat them all simultaneously. When they're all three nice and hot the pot will just slide right out of the board.

Afterwards you can clean up the pads and lugs with wick / solder sucker / etc.

 

[zgrav]

It is a PITA to get a 3 prong pot unsoldered from the board. The more solder you can get off in advance, the easier it will be. When you are heating the posts you might want to increase the heat on your soldering iron a bit but be careful since you also do not want to damage the board.

If that does not work because you cannot get the two posts loosened at the same time, you could cut the middle post right at the pcb and then heat up one post to move it out a bit. then do the other side, moving them a little at a time until they are free from the board. After the pot is out you can heat and remove the part of the middle post you left in the board, taking it out from the bottom. If/when you reattach that pot to a circuit board you will need to use a wire to make the connection from the middle post of the pot to the circuit board. messy, but still a reliable repair if you reuse that part.

 

[zgrav]

I'll have to try the "add more solder" method. I have added more solder to parts when trying to wick solder from a component, so I'll keep that in mind.

 

[Robert]

The blob of solder creates a heat bridge so more heat gets transferred to the pins. Even the best desoldering tools leave some behind in the through-plated holes, so pulling them out hot makes that a non-issue.... most of the time.

I usually turn the pots all the way down first, just in the event that the excess heat were to overheat the resistive wafer it would be at point in the rotation that isn't frequently used.

zgrav is right though, sometimes they just want to be a pain.