[sdiy] my vco is TOO alive

[Dan Snazelle]

thanks for the great advice

this might be a good time to get more used to my scope

let me ask...i am still VERY new at using my scope.

what am i looking for ideally on the power rails? and what sort of settings are good for this?

in the last year i have been so busy that my scope hasnt seen nearly as much use as i would like and 
i am still a bit unsure of it at times

thanks

--------------------------------------------
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> From: KingRavine at comcast.net
> To: subjectivity at hotmail.com; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] my vco is TOO alive
> Date: Wed, 10 Dec 2008 17:57:20 -0500
> 
> ----- Original Message ----- 
> From: "Dan Snazelle" 
> To: "sdiy" 
> Sent: Wednesday, December 10, 2008 2:11 PM
> Subject: [sdiy] my vco is TOO alive
> 
> 
>>
>> one of my vco's, a CGS (ken stone) vco, which is being run off a +/- 
>> 12volt supply and has a tempco in place, lately has been exhibiting a LOT 
>> of instability. This started a few months ago and it sounds like there is 
>> a gremlin inside of it that is messing with its stability.
>>
>> i am all for organic VCO's but this is too much. The note you are playing 
>> almost always starts dipping in pitch after a few seconds.
>>
>> it's not that it isnt IN TUNE with itself, it is, and the last time I 
>> checked i think i was getting around4 ot 5 octaves of tracking.
>>
>> The issue is more about WARBLE. the notes droop and have odd amounts of 
>> vibrato added as i hold a note.
>>
>> so..my question is...what could cause a healthy VCO to start sounding like 
>> it's dying?
>>
>>
>> I have about 5 or 6 other modules running off the same PSU and none of 
>> those modules are showing any of the same problems.
>>
>> Could it be
>>
>> Bad caps?
>> Ripple?
>> (the PSU is rated for at least .7 amps)
>> Or something I cant even fathom?
>>
>> Up till this point, i had been very happy with this VCO and found it very 
>> flexible.
>> But now that i cant hold a note for too long without it dipping in 
>> frequency, it doesnt work too well with my other VCO.
>>
>>
>> ANY advice appreciated!
>>
>> thanks
>>
> 
> 
> 
> Hi Dan,
> 
> I'd start simple:
> 
> jack is dirty / corroded?
> Loose wire to the CV jack / tuning controls?
> Bad tuning pot?
> 
> Use a voltmeter or scope on the CV summer and see what's happening. 
> Also, look at the power rails with a scope
> 
> I'd also try disconnecting every other module from the power supply to see 
> if the problem goes away.
> 
> Dave Magnuson 
>