[sdiy] asm2 vco problems

[Dan Snazelle]

THANKS

"
I'd expect something like a few 100 kHz or so.
 "

do you mean a few 100 PF?



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> Date: Fri, 7 Nov 2008 19:31:24 +0100
> Subject: Re: [sdiy] asm2 vco problems
> From: magnus at rubidium.dyndns.org
> To: subjectivity at hotmail.com
> CC: synth-diy at dropmix.xs4all.nl
> 
>>
>>
>> anyone around here built the asm2? having some real trouble with the vco
>> (vco 1)
>>
>> the schematics are here:
>>
>> http://www.elby-designs.com/asm-2/vco/vco-asm2-about.htm
>>
>>
>> getting voltage on all the rails.
>>
>> oddly the outputs (square wave specifically) keeps putting out  a
>> voltage...around 4 volts
>>
>> i resocketed the ic's.
>> i resoldered the solder points.
>>
>> been testing for continuity and so far havent found any dead connections.
>>
>> i am stumped.
>>
>> next i am going to try replacing the caps (i hate pulling out caps :(
>>
>> any ideas? specific voltages i should be getting on specific pins?
>> my project is going down in flames ;(
> 
> Check that pin 7 on the LM311 kicks, and at what rate. A particular issue
> that have occured with the ASM-1 VCO (which is essentially what the ASM-2
> VCO is), is that the reset time was not sufficient to empty the capacitor.
> Increasing the capacitance on the reset circuit (such as fingering it!!!)
> can make it operate properly.
> 
> I just added some more capacitance to ground, but it should really be
> accross the LM311 if done properly.
> 
> I'd expect something like a few 100 kHz or so.
> 
> Cheers,
> Magnus