[sdiy] Help trouble shooting mfos echo rockit

[JoeF]

Hello and tx again. So, I followed the schematic and there are indeed resistors before the labc inputs. They are 22K. I measured a voltage drop of 3.61V across them and calculate a current of 165micro amps. So, is that a reasonable value. I have also recorded the 13600 pin voltage values below.
Starting at pin 1 and finishing at 16. 
1.25-1
0-2
3.73-3
3.68-4
8.4-5
0-6
0.31-7
1.28-8
0.32-9
0.31-10
9.14-11
0.61-12
3.76-13
3.74-14
0-15
1.25-16
I am pretty much under water here. I don't know whether these are appropriate values for this circuit or not. I can hear an audio signal on pin 3. And, I hear it on pin 8.
Tx for the help. JoeF.




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On Nov 20, 2022, 3:24 PM, at 3:24 PM, Roman <modular at go2.pl> wrote:
>I don't have any schematics at hand so it's just basic guideline. There
>is something going into Iabc pin of LM13600. If it's a resistor, then
>simply measure voltage across that resistor and use Ohm law to
>calculate current. If it's supplied directly from PNP transistor's
>collector (most typical use) find a resistor that is going to emiter of
>that transistor, and do as previously described. In any scenario you
>may just desolder or cut the trace to Iabc pin and measure it with
>ampmeter. Or better yet, put a resistor there if there wasn't any, it
>can only help. 4k7 for starters. It will make future troubleshoting
>easier, not to mention it also prevents LM13600 from accidental
>smoking.
>
>Roman 
>
>---- Użytkownik JoeF napisał ----
>
>>Roman and Pete, TY. Roman, I want to move to the next level. Could you
>pont the way to how to determine current flow. I know how to check
>voltage and perform audio traces but I don't know how to determine
>current. If it's not too difficult, could you explain or point to a
>site that would explain. Tx again. JoeF.
>>
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>>
>>On Nov 20, 2022, 2:44 AM, at 2:44 AM, Roman <modular at go2.pl> wrote:
>>>Measure the Iabc current going to LM13600 to check if they are open
>at
>>>all. Measure voltages at OTAs and opamps outputs to see if they are
>not
>>>terribly close to one of supply rails.
>>>
>>>Roman
>>>
>>>---- Użytkownik JoeF napisał ----
>>>
>>>>Hello all, not sure if this is the right place to ask for guidance
>>>but, I'll try. I have put together an Echo Rockit I got as a kit.
>And,
>>>of course I need to troubleshoot.
>>>>This is an oscillator and external input into a VCF into a PT2399
>>>delay. I am getting no sound at the output and I believe it is
>because
>>>the VCF is not functioning. I have audio traced a signal to the VCF
>>>from the input and the internal oscillator. And, I have jumped the
>>>signals around the VCF straight to the delay and then I get output
>and
>>>have verified the delay is operating as expected. I have correct
>power
>>>to all IC power pins. The transistors are getting power on their
>source
>>>pins.The IC in the VCF is an 13600D which I have spares of and have
>>>swapped to no avail. I have re-soldered the components in the VCF
>>>circuit. I don't have extras of the MPF102 transistors and am
>>>questioning whether I burned them up when I soldered them in? What do
>>>you think?
>>>>What's next? Thanks for any advice in advance. JoeF.
>>>>
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>>>>
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>>
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