[sdiy] Help trouble shooting mfos echo rockit

[Pete Hartman]

I'm away from my computer for the moment, but 1) schematic is at
musicfromouterspace.com, and 2) if I recall correctly yes there is a
resistor feeding iabc.

Pete

On Sun, Nov 20, 2022 at 2:28 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.
>
> Get TypeApp for Android <http://www.typeapp.com/r>
> On Nov 20, 2022, 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.
>>
>> Get TypeApp for Android <http://www.typeapp.com/r>
>>
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