[sdiy] Need one of two things....

[Pete Hartman]

Actually....  Looking it over it seems to make a little bit of sense to
me.  The + inputs (often used for biasing) are next to each other, and the
outputs are next to each other.

The good news is I found two build errors and an instruction error (If
you're building ZThee/THC's panel with the envelopes, you have to adjust
the rise/fall pots to CLOCKWISE, not "CCW" to get the fastest waveform),
and once you trim pin 10 of the lower LM3900 to 4V in *that* position, the
rest of it falls together (without build errors that is).

PS: No I didn't just spend 7 hours straight beating my head on this ;)  I
walked away from it several times and did some other things, and just now
was stubbornly giving it one last try when I found the last build error.



On Sat, Oct 31, 2020 at 2:06 AM Paul Perry <pfperry at melbpc.org.au> wrote:

> The most incomprehensible thing about the LM3900 is the pinout.
>
> ------ Original Message ------
> From: "Pete Hartman" <pete.hartman at gmail.com>
> To: "Oren Leavitt" <obl64 at ix.netcom.com>
> Cc: "synth-diy at synth-diy.org DIY" <synth-diy at synth-diy.org>
> Sent: 31/10/2020 2:53:12 PM
> Subject: Re: [sdiy] Need one of two things....
>
> A bit of an extreme approach when troubleshooting a different circuit, but
> sure :D
>
> Pete
>
> On Fri, Oct 30, 2020 at 9:10 PM Oren Leavitt <obl64 at ix.netcom.com> wrote:
>
>>
>> On 10/30/20 8:42 PM, Pete Hartman wrote:
>>
>> Thanks Neil!
>>
>> Currently trying to absorb it.... :)
>>
>> Pete
>>
>> Clone a PAiA Gnome - It'll give you a feel for how Norton op-amps work.
>>
>>
>> On Fri, Oct 30, 2020 at 7:52 PM Neil Johnson <neil.johnson71 at gmail.com>
>> wrote:
>>
>>> Hi Pete,
>>>
>>> TI's AN-72 is a pretty good read on how Norton op-amps work and many
>>> applications, including all the "standard" circuit blocks:
>>> https://www.ti.com/lit/pdf/snoa653
>>>
>>> Neil
>>>
>>> On Sat, 31 Oct 2020 at 00:09, Pete Hartman <pete.hartman at gmail.com>
>>> wrote:
>>> >
>>> > 1) Is there anyone with experience or a pointer to a description of
>>> how the Serge '73 R7 envelope generator works?  Basic googling gets me
>>> various summaries of Ken Stone's page where "a little on how it works" is
>>> just the schematic.  Got that, don't grok it in the slightest...
>>> >
>>> > ...Because I don't really "get" Norton Amplifiers.  (I have been able
>>> to repair VCS' in the past but leaned very heavily on Tim Stinchcombe's
>>> description of how it worked).  I mean yes, I understand logically "current
>>> differencing" but in practical uses I can't look at a topology and say "oh
>>> yes, this is an inverter/summer with gain X" the way I can with a standard
>>> Op Amp.
>>> >
>>> > So
>>> >
>>> > 2) out of all of the various circuit simulation tools that have been
>>> discussed, which one or ones has a decent Norton Amp simulation?
>>> Simulation is usually my go to with circuits that don't follow "standard"
>>> often used topologies (standard like an expo converter, or
>>> integrator/differentiator, etc).  I'm one of those who has long leaned on
>>> the Falstad javascript simulator, and they do NOT have a Norton Amp (at
>>> least not as far as I could tell, no promises that I didn't miss something).
>>> >
>>> >
>>> > I've got one of ZThee's 73-75 panels and none of the three EGs will
>>> cycle in the usual way.  Power looks good, components have not been 100%
>>> verified but everything I've checked directly against the circuit appears
>>> to be correct.  Nothing is hot.  Soldering is solid (I resoldered a few
>>> joints here and there, but mostly out of an abundance of caution).  None of
>>> the usual first step troubleshooting methods has borne fruit so I'm now
>>> into "ok I have to understand the circuit well enough to know what each bit
>>> of it SHOULD be doing when I have end connected to start or cycle."
>>> >
>>> > Thanks!
>>> >
>>> > Pete
>>> > _______________________________________________
>>> > Synth-diy mailing list
>>> > Synth-diy at synth-diy.org
>>> > http://synth-diy.org/mailman/listinfo/synth-diy
>>>
>>
>> _______________________________________________
>> Synth-diy mailing listSynth-diy at synth-diy.orghttp://synth-diy.org/mailman/listinfo/synth-diy
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20201031/21aa604b/attachment.htm>