Author Topic: Sabrotone's Klon Centaur to debug (voltages)  (Read 179 times)

JackSkellington

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Sabrotone's Klon Centaur to debug (voltages)
« on: October 04, 2018, 08:36:55 AM »
Hey, guys. I'm building a lot of stuff in these days. Some circuits are ok, but this is not!

I completed the board, though it has some sockets to test it :D
This is the layout:


This is the page:
https://www.sabrotone.com/?p=729

Update
Schematic:


Just one change: C15 from 47uF to 100uF (35v). The other electrolityc caps are 50v. Orientations are ok.
The ICs are the TL072 and 7660S CPAZ.
The clipping diodes are D9E. Every diodes are rightly oriented.
All the pots, the footswitch and the LED is wired.
Dual Gain pot like that:
1 2 3
4 5 6

The Footswitch is a 3PDT and is wired like that:
1 4 X
2 5 X
3 6 X

The circuit sounds, but extremely wrong. Buffered sounds low and crackling at the peak. Engaged the red turn on, the volume is still low, slightly overdriven, the volume pot works but the wide is really small, the Treble pot pretty the same, it's hard to say if it works, as the Gain pot, it crackle when I turn on.

These are the corrected voltages:
      IC1          IC2       IC3
1    +4.43V    +4.6V     +8.84V
2    +4.44V    +4.43V    +4.52V
3    +3.45V    +4.43V    0V
4    0V          -8.44V       -4.13V
5    +4.43V    +4.42V    -8.42V
6    +4.43V    +4.43V    +3.97V
7    +4.41V    +4.26V    +5.29V
8    +8.87V    +15.92V    +8.82V

And these are my voltages:
      IC1          IC2       IC3
1    +1.37V    +4.50V     +9.00V
2    +1.38V    +0.0V    +4.76V
3    +0.93V    +0.0V    0V
4    0V          -8.65V       -4.34V
5    +1.22V    +0.00V    -8.65V
6    +1.16V    +0.00V    +4.63V
7    +8.37V    +4.66V    +4.18V
8    +9.00V    +16.46V    +9.00V

Need some urgent help (and I never say urgent!).

Thanks! ;)
« Last Edit: October 06, 2018, 12:12:07 PM by JackSkellington »
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JackSkellington

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Re: Sabrotone's Klon Centaur to debug (voltages)
« Reply #1 on: October 04, 2018, 11:03:57 AM »
Sorry, I forgot... I replaced the 390pF with two caps soldered in parallel: 330pF + 50pF = 380pF.
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JackSkellington

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Re: Sabrotone's Klon Centaur to debug (voltages)
« Reply #2 on: October 07, 2018, 01:32:55 AM »
Somebody can help me, please?
I assume there's something wrong in the buffer, but I cant see anything. Maybe I wrong.
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Ralfg

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Re: Sabrotone's Klon Centaur to debug (voltages)
« Reply #3 on: October 07, 2018, 09:34:28 AM »
It’s hard to say without pictures. It would be good to have a picture of the top and bottom side of the board that would help someone here figure out what is going on. Check your cuts and make sure you are not missing on, can happen pretty easily on vero. And reflow your connections. Look for any solder bridges that might have accidentally happened. I’d first look at your power section and check if everything is hooked up correctly to you two ICs. Those voltages are way off and it makes me think you are missing a cut, or something is grounding the power.
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reddesert

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Re: Sabrotone's Klon Centaur to debug (voltages)
« Reply #4 on: October 07, 2018, 10:45:35 PM »
Clearly, your voltages on IC3, the charge pump, are correct but the voltages on IC1 and IC2, the op-amps, are mostly wrong.

Pins 4 and 8 on the op-amps, which are the Vsupply pins, are fine.  However, notice that pins 3 and 5 of IC2, the second op-amp, should be connected directly to Vbias. Vbias should be about +4.5V. However, your pins 3 and 5 of IC2 read 0V.  This suggests that you have a problem which is grounding the bias rail. It's not clear whether the problem is in the components that generate Vbias, or whether you have something touching the bias strip (solder bridge, component in the wrong place, etc). But that's the first place you should look.

Pin 3 of IC1 is also connected to Vbias through a 1M resistor, so it's possible that this is also causing the problems on IC1.  In any case, a mis-biased circuit will generally sound horrible, so that's probably what is wrong.

As always, it's possible to figure out a lot about a circuit just by thinking about what the voltages are, and what they should be, starting with the simplest connections on the schematic (here, pins connected directly to Vbias).