Cgs synth

Also tack a 47pf across the feedback resistor in each of the summer op-amps
at the input of the VCO. (between inverting input pin and output)

Ken

>This could be due to a grounding problem. I suggest double checking the
>grounding back to the power supply first. Then check that all the
>places that are supposed to be grounded in the VCO actually are
>grounded. It could also be due to ground loops, that can cause
>"parasitic" oscillations, unwanted high frequency oscillations in
>unexpected places. If you have a scope, you should look for parasitics
>sitting on the VCO outputs. Ideally, grounds should follow a star
>pattern, with all grounds connecting back to the power supply connector
>in a direct manner. One way to troubleshoot is to change one or more
>ground wires and see if the problem is fixed. By "change" I mean adding
>a separate ground wire for each jack, etc..
>
>Look closely for bad solder joints, too, on the entire PC board and all
>off-board connections.
>
>Richard Brewster
>http://www.pugix.com
>
>Rykhaard D.A.M.I.A.N. wrote:
>> Here's a new weird experience for me:
>>
>> I've got VCO V0.2 about 98% completed. (Still needs 1V/octave
>> tuning). In wiring up all of the controls and jacks to the front
>> panel (wood, as all of mine are), for the first time ever in any of
>> 100's of modules that I've built over the years, I have this module
>> acting as an ANTENNA! :O
>>
>> The closer that I put my hand to either of the 2 tuning knobs or the
>> pitch CV Amount knob, the higher the pitch of the VCO becomes. ????
>>
>> Has anyone else ever had this kind of trouble with any module?
>>
>> The one new thing that I've done with this module, that I've never
>> done before - is wrap all of the wiring from the PCB, around other
>> wires to / from the PCB. I figured I could do that to keep all of the
>> wiring as neat as possible, instead of using cable ties, to hold them
>> all together. Could THIS be the cause for picking things up from my
>> own touch?
>>
>> When I get ready to do the 1V/O (Mooging? ;) ) today, I thought I
>> would unwrap each of the 3 voltage feeds (Tune, Fine, CV) from the
>> wrapped wires to leave them free-hanging, to see if this stops things.
>>
>> Another difference that I'm surprised by: this VCO is highly affected
>> by the voltage swings in 1 of my 2 LFOs. (My previous Tom Gamgle
>> VCO4D and Ian Fritz mini-VCO) aren't affected at all.
>> Both of them though - have 100uF bypass caps on the power inputs to
>> their boards. I'm going to try increasing the bypass cap values on
>> the VCO V0.2 board to 100uF as well as at least 1 x 100nF each. Also
>> - I'll check my 2 LFOs to see if they have proper bypass caps at their
>> quad opamps as well.
>>
>> Thanks to any possible solutions to what I've typed, above. :)
>>
>>
>>
>
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>
>Yahoo! Groups Links
>
>
>
>

_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
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