[sdiy] Help trouble shooting mfos echo rockit

[Pete Hartman]

You should also hear signals on pins 14 & 9.

For anyone else who wants to pitch in the schematics are here:
http://musicfromouterspace.com/analogsynth_new/ECHOROCKIT/images/echorockitschem_page_1.gif
http://musicfromouterspace.com/analogsynth_new/ECHOROCKIT/images/echorockitschem_page_2.gif

And the whole project is at
http://musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&PROJARG=ECHOROCKIT/ECHOROCKIT.php&VPW=1435&VPH=679

In Ray's idiosyncratic notation, BP is the + rail and BN is the - rail, I
believe.

Pete



On Sun, Nov 20, 2022 at 6:26 PM JoeF <frey at radioles.com> wrote:

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