All I can say is you have me stumped! I've not heard anythng like this
before, and I've sold dozens of these.
Ken
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
before, and I've sold dozens of these.
Ken
>Now I'm getting someplace!_______________________________________________________________________
>
>I've got a perfect sawtooth up to the pin 2 of the saw output
>opamp. 15 volts DC at pin 1. I disconnected the 330R resistor,
>expecting to see zero vdc at pin 7. Measured about 10vdc instead!
>+15 vdc at pin 8 and -15vdc at pin 4.
>
>Also, If I plug into the shape CV input I can hear (and see) the
>same signal somewhat "shaped" That means everything is doing what
>I'd expect *except* the TL072 (which has been replaced twice now
>from different stock) for the saw and square ouput. I've put the
>600K/200K ohm resistors (600K in the feedback/200K to ground from
>the input) on the saw stage for +-5 volt swing.
>
>Everything seems okay in the traces. What am I doing wrong? Is the
>47mfd cap to be removed? Has anyone else built a rev 3 pcb?
>
>Ken?
>
>Gee, don't tell my employer about this!
>
>Chub
>
>--- In cgs_synth@yahoogroups.com, "charlesosthelder"
><osthelder@n...> wrote:
>> Now this is wrong. Tested the second VCO (had the correct TL0__
>> device in place!) and get the same result as the first. VCO core
>is
>> fine - actually works very well! The sawtooth from the core
>> completely goes away at the pin 1 of the TL072 for the saw
>output.
>> I checked for a simple short to ground, but no such luck. Cap
>> polarity is correct and the TL072 has correct voltage at pins 4
>and
>> 8.
>>
>> Another oddity - the sub input and output work as expected. But
>if
>> I plug my square wave audio into the square wave out jack, which
>is
>> connected to the sub input when no plug is in the sub in,
>frequency
>> is halved!
>>
>> This is really odd. How can such a simple stage as the saw and
>> square output amplifier be causing me so much grief? Has anyone
>> else built the rev .3 pcb? When I get a chance, I'm going to
>follow
>> the traces. In the meantime, I'm going to try to calm down.
>>
>> Any ideas?
>>
>> Chub
>
>
>
>
>
>See the following URLS for the CGS Modular Synth home page:
>Main: http://www.cgs.synth.net/
>Secondary: http://otherunicorn.0catch.com/synth/
>Yahoo! Groups Links
>
>
>
>
>
>
>
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>