Lowrider - distorted sound. ICs burnt?

[AlleMux]

Project Name: Lowrider

General description of the problem:
After I finished soldering all the parts on the pcb, I tested it and it worked great. So I boxed it.
Everything was fine, I plugged my guitar in and it sounded just as it should.

The same day, after a couple of hours, I turn it on again and I heard just some scratches, and some weird sounds, and no guitar signal at all.



Steps that I have taken to try to resolve the issue

I double checked my wiring, my part values, my part orientation, my soldering job.


When the pedal is turned off, the true bypass works perfectly.

After I tried to open the box in order to find out if there were some bad connection, I didn't notice anything strange, any part unconnected, or any weak connection. Then I tried again to play something, and this time I could actually hear my guitar signal, but distorted and with no octave.
The signal came and went, sometimes I heard no sound at all, sometimes a distorted sound.

Then I noticed that one of the pin of the 3PDT switch moved a very bit if you touched it. So I replaced the 3PDT with a new one. Now I don't hear no sound anymore, but it is still distorted and with no octave.

List any substitutions I used for parts/values

I left C12 off, and used a 1n capacitor instead of 10n for C10, as suggested by the .pdf project. The upper octave sounded a bit fuzzy, as the project said it would, but when the pot of the upper octave was all turned down the sound was perfectly clean, so everything was ok.

Here are my DC measurements on all the IC and Transistor pins (black lead of the Mulitmeter to ground, reliable power to the circuit)


Positive lead at jack/battery
9.04

9V in at board
9.04

Ground in at board
0.00

IC1  TL072

pin 1 - 8.32
pin 2 - 8.33
pin 3 - 4.16
pin 4 - 0.00
pin 5 - 4.99
pin 6 - 8.34
pin 7 - 8.40
pin 8 - 9.05

IC2  LM324  

pin 1 - 7.77
pin 2 - 7.40
pin 3 - 7.82
pin 4 - 9.05
pin 5 - 7.83
pin 6 - 7.33
pin 7 - 7.77
pin 8 - 7.77
pin 9 - 7.40
pin 10 - 8.09
pin 11 - 0.00
pin 12 - 7.32
pin 13 - 8.10
pin 14 - 0.00

IC3 CD4013

pin 1 - 9.05
pin 2 - 0.00
pin 3 - 0.00
pin 4 - 0.00
pin 5 - 0.00
pin 6 - 7.50
pin 7 - 0.00
pin 8 - 0.00
pin 9 - 0.00
pin 10 - 0.00
pin 11 - 0.00
pin 12 - 0.00
pin 13 - 9.05
pin 14 - 9.05

IC4  CD4013

pin 1 - 9.05
pin 2 - 0.00
pin 3 - 0.00
pin 4 - 0.00
pin 5 - 0.00
pin 6 - 0.00
pin 7 - 0.00
pin 8 - 0.00
pin 9 - 0.00
pin 10 - 0.00
pin 11 - 0.00
pin 12 - 0.00
pin 13 - 9.05
pin 14 - 9.05

IC5 TL074

pin 1 - 8.45
pin 2 - 8.28
pin 3 - 7.88
pin 4 - 9.05
pin 5 - 5.07
pin 6 - 8.44
pin 7 - 8.45
pin 8 - 8.45
pin 9 - 8.35
pin 10 - 8.25
pin 11 - 0.00
pin 12 - 5.04
pin 13 - 8.45
pin 14 - 8.45

IC6  TL074
pin 1 - 8.45
pin 2 - 8.28
pin 3 - 8.58
pin 4 - 9.05
pin 5 - 8.58
pin 6 - 8.42
pin 7 - 8.45
pin 8 - 8.45
pin 9 - 8.33
pin 10 - 8.52
pin 11 - 0.00
pin 12 - 8.52
pin 13 - 8.21
pin 14 - 8.39

Q1 J201

pin 1 - 9.05
pin 2 - 8.32
pin 3 - 4.28

Q2 2SK30

pin 1 - 8.30
pin 2 - 8.64
pin 3 - 3.00

Q3  2SK30

pin 1 - 7.90
pin 2 - 8.57
pin 3 - 0.00



IC3 and IC4 measurements look a bit...burnt, don't they?


Thanks for your time,

Alle, Sassuolo, ITALY

[AlleMux]

I tried to replace Q2 and Q3 with new ones. Then I connected the pcb to the input and output jacks and plugged my guitar in: it worked!!
BUT when I turned the pedal off and on again... Once again, a noisy distorted sound.

Any idea??

[DutchMF]

First off: your first post is an example of how a tech help thread should be, kudos! Since the problem went away temporarily after you replaced Q2 and Q3, triple check all component values around those two. And since your problem returned after switching the pedal on and off, also recheck your ground/9V connections. The board's input is connected to ground on bypass (assuming you used MB's wiring scheme) so if you have a solder bridge in that area, you might get unwanted results! I can't comment on your voltages, as I haven't build the Lowrider myself, so maybe someone else will comment on those. Good luck!

Paul

[nzCdog]

Seeing as its reasonably complex I'll get my one out and compile a full list of Voltages... stand by

[nzCdog]

http://www.madbeanpedals.com/forum/index.php?topic=9488.msg83297#msg83297
Here is the link to reference Voltages.  
You have quite a few bad voltage readings, which means it's going to take a systematic fault finding approach...  There are no shortcuts, I'm afraid they only end in more frustration.

*Your VR is double what it should be... it affects many components right across the board
*Some of your IC readings are very unusual, check the orientation of your diodes as well

Make sure you are reading the correct pins of the ICs and FETs in the first place.

ICs number like this:

FETs like this

[RobA]

One thing I notice is that you are using 2SK30's. It's still a somewhat open question but, the Lowrider board seems to be setup for GSD pinouts like in the 2N5457 and the 2SK30's are SGD. I used 2SK30's in my build and had to bend the legs around to get them to work.

Having said that, I don't think it is your main issue. Strangely, having the transistors in the wrong way doesn't kill the sound. It just changes the tone of the bass voices somewhat. But, it is worth looking at as one source of problems.

Here are links to the spec sheets so you can compare.
http://www.mouser.com/ds/2/149/2N5457-188270.pdf
http://www.synthdiy.com/files/2007/2sk30atm_en_datasheet_030325.pdf

[AlleMux]

Guys, I've just finished to test once again my pcb.

First of all, I started to check again all the components.

- All the diodes and the ICs are in the correct orientation, and all the electrolytic capacitors as well. Good.
- I checked my old VR, being sure to collects numbers according to the correct pinout (as suggest by nzCdog) and yes, I did it right.
- In my last post, as I told you, I replaced Q2, Q3 but I forgot to tell that I replaced IC3 and IC4 too, with new ones. Since then, my VR have changed a little bit: I'll write them all again putting the changes in evidence:

IC1  TL072

pin 1 - 8.32
pin 2 - 8.33
pin 3 - 4.16
pin 4 - 0.00
pin 5 - 4.99
pin 6 - 8.34
pin 7 - 8.40
pin 8 - 9.05

IC2  LM324  

pin 1 - 7.77
pin 2 - 7.40
pin 3 - 7.82
pin 4 - 9.05
pin 5 - 7.83
pin 6 - 7.33
pin 7 - 7.77
pin 8 - 7.77
pin 9 - 7.40
pin 10 - 8.09
pin 11 - 0.00
pin 12 - 7.32
pin 13 - 8.10
pin 14 - 0.00

IC3 CD4013

pin 1 - 9.05
pin 2 - 0.00
pin 3 - 0.00
pin 4 - 0.00
pin 5 - 0.00
pin 6 - 1.50 (maybe I signed the wrong number in this one - my multimeter is digital, so I may have read 7 instead of 1)
pin 7 - 0.00
pin 8 - 0.00
pin 9 - 0.00
pin 10 - 0.00
pin 11 - 0.00
pin 12 - 0.00
pin 13 - 9.05
pin 14 - 9.05

IC4  CD4013

pin 1 - 0
pin 2 - 9
pin 3 - 9
pin 4 - 0
pin 5 - 9
pin 6 - 0
pin 7 - 0
pin 8 - 0
pin 9 - 0
pin 10 - 0
pin 11 - 0
pin 12 - 0
pin 13 - 9
pin 14 - 9

IC5 TL074

pin 1 - 7.80
pin 2 - 7.80
pin 3 - 7.88
pin 4 - 9
pin 5 - 4.7
pin 6 - 7.80
pin 7 - 7.90
pin 8 - 8
pin 9 - 8.15
pin 10 - 7.90
pin 11 - 0
pin 12 - 4.75
pin 13 - 7.80
pin 14 - 7.80

IC6  TL074
pin 1 - 8.45
pin 2 - 8.28
pin 3 - 8.58
pin 4 - 9.05
pin 5 - 8.58
pin 6 - 8.42
pin 7 - 8.45
pin 8 - 8.45
pin 9 - 8.33
pin 10 - 8.52
pin 11 - 0.00
pin 12 - 8.52
pin 13 - 8.21
pin 14 - 8.39

Q1 J201

pin 1 - 9.05
pin 2 - 8.32
pin 3 - 4.28

Q2 2SK30

pin 1 - 7.80
pin 2 - 8.40
pin 3 - 7.80

Q3  2SK30

pin 1 - 7.80
pin 2 - 8.40
pin 3 - 7.80



So, I started to check even the only thing I was sure about: resistors. And here's the buzz:

I bought my components on www.banzaimusic.com, so they arrived packed in plastic bags, with labels, with data on each one. For this reason, it is way more easy to solder the resistors following the order of their values.
I mean, for example, I put down all the 1M resistor, then all the 47k, and so on. Following the order of the resistors of the project (R2 after R1, ....R46 after R45...) forces you to open more than a plastic bag, and that is more risky.

Of course, I did everything very slowly and double checking, I was sure I put the right components in the right places before soldering. But actually I didn't use my multimeter on each resistor to test if the guys of Banzai did their job right.


Anyway, few hours ago I was in my lab looking for an issue, so I did it: I used my digital multimeter and test them.
Well... Some values are perfectly right...but some others....!
Here's what looks wrong to me:

R3 - 6.9k instead of 10k
R11 - 800k instead of 1M
R12 - 7.8k instead of 10k
R13 - 7.8k instead of 10k
R14 - 7.8k instead of 10k
R17 - 48k instead of 220k
R19 - 89.3k instead of 100k
R21 - 33.7k instead of 47k
R23 - 55.5k instead of 100k
R34 - 6.7k instead of 10k
R35 - 7.43 instead of 12k
R46 - 42k instead of 120k
R47 - 90k instead of 1M
R48 - 87k instead of 220K
R49 - 40k instead of 56k
R54 - 47k instead of 1M
R55 - 70k instead of 160k

Ok, you may say that these are too much. That I was drunk when I soldered my pcb. That I'm blind.

I just couldn't believe I wrong so many values. So I checked the stripes on each one: they ARE RIGHT.
So what the hell happened?! Are they burnt or something? Is my multimeter broken? It's me, that I'm not able to use it in the correct way? If it's me, why all the other values are perfectly right?

In any case, thank you all for your answers, I appreciate that.

Alle

[wstimson]

If you are testing those resistors while they are soldiered onto the board, you will not get reliable readings because they are part of the circuit now.

Once they are soldiered in, you have to check them based on their bands.

[AlleMux]

(Thank you wstimson! I've never studied electronics, I've just followed instructions so I didn't know that )

Well...in my local store I couldn't find ANY of the active components of the project, so I'm going to buy again on banzaimusic.com in order to replace all the ICs and transistors.

nzCdog, I'm thinking about when you gave me your VR and noticed that mine were all double value, so that one or more components at the beginning of the circuit could be broken.

For example, according to your VR, my Q1 (that I've never replaced) give me double voltage at the source pin. And it is actually at the beginning of the circuit.

This affects all the other components, right? So is a good idea to replace these active components?

[nzCdog]

I think we need some good photos of your board before we go any further.  Don't replace any parts yet

[AlleMux]

Here they are.
The yellow wires are short extensions I did for the pot's pins.
As you can see the trimpot is mounted on the opposite side because the one I got has the correct value but wrong size. I just soldered it after bending the pins.

http://imageshack.us/photo/my-images/339/img0916kd.jpg/
http://imageshack.us/photo/my-images/339/img091823.jpg/
http://imageshack.us/photo/my-images/24/img0917zu.jpg/
http://imageshack.us/photo/my-images/571/img0921uu.jpg/

[AlleMux]

Writing about the trimpot made me think about a thing.
Just to be certain.. another thing I did differently fron the project was to invert the pinout of two of the four pots.

I mean, in order to create a cool W-shape layout of the knobs, and having four pcb-mount pot, two of them must be rotate clockwise, and the other two counterclockwise. I actually did it (and did not tell you) knowing that a pot is a resistor with a sliding contact that gives an adjustable value. So I thought that inverting pin 1 and 3 would have just caused an opposite rotation.

Is this right?

[wstimson]

Writing about the trimpot made me thought about a thing.
Just to be certain.. another thing I did differently fron the project was to invert the pinout of two of the four pots.

I mean, in order to create a cool W-shape layout of the knobs, and having four pcb-mount pot, two of them must be rotate clockwise, and the other two counterclockwise. I actually did it (and did not tell you) knowing that a pot is a resistor with a sliding contact that gives an adjustable value. So I thought that inverting pin 1 and 3 would have just caused an opposite rotation.

Is this right?

Yes, swapping lugs one and three on the pots won't cause any problems other than the rotation being the "wrong" direction. 

Since you have those wires on there, you could probably cross them over and get them to work correctly if you wanted.

[nzCdog]

Good pics thanks Allemux.  I need a good clear shot of the entire rear of the board as well. 

At this stage I am looking for shorts caused by solder bridges or stray component leads.  Check your pot pins aren't shorting either, one of the pics makes them look dangerously close.

[AlleMux]

This is the rear:
http://imageshack.us/photo/my-images/850/img0924v.jpg/

and this is a close shot in order to focus on some joints that look connected in the previous image, but they're not:
http://imageshack.us/photo/my-images/853/madbc.jpg/

For any other pic just tell me!