Easy Vibe Debugging

[Bruce_W]

After building a couple pedals ( Distortion & Tubscreamer) I figured I could handle a bigger project. So.. not good, this one has me frustrated. I used the layout here
http://www.aronnelson.com/gallery/main.php/v/Roobins-Album/DIY-Layouts/render.gif.html  - Problems are when I first plug in the battery the 2 bias LED's light then flicker and then turn off. Noise and no sound.
Voltages are -
IC4  p1 - .738    p2 - .867    p3 - .543    p4 - 4.7mv  p5 - 2  p6 - 8.35     p7 - 8.4    p8 - 9.9
IC3  pretty much the same
IC2   same
IC1   p1 - 8.53    p2 - 1.63   p3 - 9.91   p4  - 2.3mv  p5 - 1.11   p6 - 1.01  p7 - 1.05   p8 - 9.8

I did search and couldn't find a similar problem. Thanks in advance






     

[oldrocker]

It doesn't say but is this a verfied layout?

[Bruce_W]

At the top of the page it does say "Easyvibe Layout - VERIFIED". It looked easier/more space, thats why I used it instead of the original.

[oldrocker]

Ah you're right.  I must be blind.  So you etched a PCB?  I have perf boarded this so I'm not too keen on this layout. (No pun intended)  It sure acts like an incoming power issue like a cap charging and discharging.  Both 470uf caps orientation good?  According to John H. it should be drawing 2.5mA.  Just guessing.

[Bruce_W]

Ah you're right.  I must be blind.  So you etched a PCB?  I have perf boarded this so I'm not too keen on this layout. (No pun intended)  It sure acts like an incoming power issue like a cap charging and discharging.  Both 470uf caps orientation good?  According to John H. it should be drawing 2.5mA.  Just guessing.

Yeah I etched the PCB. I checked all the traces and fixed the problems(I think).  So possibly a bad cap would cause the LED's to shut off?

[R.G.]

So possibly a bad cap would cause the LED's to shut off?

Well, yes, but not a bad cap. Incorrect capacitor orientation. If you get an electro cap backwards, it acts like a low value resistor.

[R.G.]

First of all, it really helps in debugging if you'll provide all the info asked for in "Debugging thread; what to do when it doesn't work". A lot of those things tell us more than one thing about what's going on. Case in point, what's the power supply voltage where the power comes into the board.  I'm guessing it's the same as the value on pins 8 of the ICs, but that has to be a guess. Schematic links are for helping us not have to go do searches for schematics that may not be the version you used. The other stuff about component orientation and wiring saves you a lot of time as well.

IC1   p1 - 8.53    p2 - 1.63   p3 - 9.91   p4  - 2.3mv  p5 - 1.11   p6 - 1.01  p7 - 1.05   p8 - 9.8

Pin 8 is the power supply pin, and it should be the highest voltage. Pin 4 is the lowest voltage, and it being a few millivolts indicates your DMM is reading a little offset from where the ground lead is clipped to where the positive probe is. These are OK.
Pin 1 is an output. It's sitting as high as the internal circuit can drive it. Not good, and one reason there is no audio. It's saturated high and nothing can pass.
This would happen if pin 2 was lower than pin 3 - and this is true. Notice that pin 3 reads higher than pin 2 - and pin 8. This raises the interesting question - is pin 3 shorted to the power supply traces? Or is there an issue in pin numbering? How did you count pins?

[Bruce_W]

Well, yes, but not a bad cap. Incorrect capacitor orientation. If you get an electro cap backwards, it acts like a low value resistor.

OK the side with the minus sign goes to the ground on both of those caps(C9 and C10).  It reads around 50mA

[R.G.]

Well, yes, but not a bad cap. Incorrect capacitor orientation. If you get an electro cap backwards, it acts like a low value resistor.

OK the side with the minus sign goes to the ground on both of those caps(C9 and C10).  It reads around 50mA

Good. Can you tell us
(a) the voltage on both 470uF caps from + to - with respect to ground
(b) the power supply voltage where the power comes into the board
(c ) whether pin 3 shorted to the power supply traces
(d) is there an issue in pin numbering? How did you count pins?

[Bruce_W]

First of all, it really helps in debugging if you'll provide all the info asked for in "Debugging thread; what to do when it doesn't work". A lot of those things tell us more than one thing about what's going on. Case in point, what's the power supply voltage where the power comes into the board.  I'm guessing it's the same as the value on pins 8 of the ICs, but that has to be a guess. Schematic links are for helping us not have to go do searches for schematics that may not be the version you used. The other stuff about component orientation and wiring saves you a lot of time as well.

Yeah I guess a missed a few important things but  I did  try to do that. The power supply is the same as pin 8. The wiring and orientation is like on the layout but I don't have the foot switch hooked up. I put the wires on the right of the switch to the right jack and the wires on the left of the switch to the left jack..

Pin 8 is the power supply pin, and it should be the highest voltage. Pin 4 is the lowest voltage, and it being a few millivolts indicates your DMM is reading a little offset from where the ground lead is clipped to where the positive probe is. These are OK.
Pin 1 is an output. It's sitting as high as the internal circuit can drive it. Not good, and one reason there is no audio. It's saturated high and nothing can pass.
This would happen if pin 2 was lower than pin 3 - and this is true. Notice that pin 3 reads higher than pin 2 - and pin 8. This raises the interesting question - is pin 3 shorted to the power supply traces? Or is there an issue in pin numbering? How did you count pins?

Here is how I counted the pins

Thanks for helping...

[Bruce_W]

Also here is the schematic

[Bruce_W]

Good. Can you tell us
(a) the voltage on both 470uF caps from + to - with respect to ground
(b) the power supply voltage where the power comes into the board
(c ) whether pin 3 shorted to the power supply traces
(d) is there an issue in pin numbering? How did you count pins?

Respect to ground is neg of battery right?

OK C9  + = 9.32  and - = 2.8mV    C10  + = 1.3  and - 1.4

Yes pin 3 was shorted to the the power supply traces!

[oldrocker]

On cap c9 plus side of battery plus side of cap c9 and pin8's on ic's.  Make sure it's not the negative side of cap c9 going pin8's of the ic's.  Whoops ok it sounds R.G. already helped u track down the problem.  Yes that trace going btwn the cap poles of c9 is tight.

[Bruce_W]

I guess that wasn't the only problem though it still has the same problems.

[Bruce_W]

New Voltages
                                         mV
             1        2       3        4        5        6          7          8
4         .77      1.2     .66      1.1     1        .72       .82       9.3
3         .74      .74     .74      2.7     1        .98        .9        9.3
2         .59      .6       1.2     2.5    1.2      1.2        1.2       9.1
1         .75       .79    .78      3.1    1.2      7.7        7.7       9.1

[oldrocker]

 Keep in mind there might 2, 3 or more problems.  So you'll have to keep checking things.   It is doing the same thing as before? Ok

[GibsonGM]

What is your voltage at VRef?  It is where the 10K resistor meets the 1N914 diodes/470uF cap.  That line continues to various points at the IC's, etc. I would check that you have around 1/2 the supply voltage at each point tied to it.  The beauty of perf board is that you can disconnect the power supply to be sure it is ok, then work your way into the circuit and find the trouble.  Gotta establish your +9v, Vref, and ground as being OK before you continue; they may be shorted somewhere. 

[Bruce_W]

Yeah same thing. I think I actually bridged that pin 3 when i was trying to touch up some solder joints.

[Bruce_W]

At the junction of C10,R23 and LED5 the voltage is 1.5. Way too low isn't it?

[R.G.]

At the junction of C10,R23 and LED5 the voltage is 1.5. Way too low isn't it?

Yep, oughta be about 3 to 4 volts, depending on which LEDs you used.