ASM-1 up and running

gstopp at fibermux.com gstopp at fibermux.com
Fri Oct 4 20:07:16 CEST 1996


     Well ya got me thinkin' so I took my ASM over into the lab and made 
     some measurements....
     
     On the low side I got an oscillation period of over a minute, with the 
     charge time slightly quicker (maybe 10%) than the discharge time, but 
     overall real darn slow. This was with the pot turned all the way down 
     (wiper to ground) but since it's such a junker I suspect that there 
     were a few ohms in there rather than 0 ohms. At about a tenth of a 
     hertz the waveform was quite symmetrical. Top frequency was 1800 
     hertz. Cap used is 0.47 uF poly-something (well it looks like a little 
     blue chicklets). I just plucked it out of a parts drawer here - maybe 
     I can log into the HP system and find the vendor info. Op-amp is a 
     Taiwanese TI TL082CP.
     
     The 1K input resistor on the LFO's integrator is the main 
     frequency-determining component, other than the cap itself. A larger 
     resistor here will shift the LFO's range lower, and a smaller resistor 
     will shift it up. The RATE pot value is really not a factor as it is 
     used as a voltage divider in this circuit.
     
     My boards were really really well-cleaned using way too much solder 
     flux remover spray, and this may be the difference. I brand I used is 
     TECH SPRAY "Flux Stripper", which appears to work pretty good. I don't 
     use isopropyl alcohol anymore - I don't think it works as well.
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Re: ASM-1 up and running 
Author:  Bob Zimmer <bzimmer at voicenet.com> at ccrelayout
Date:    10/4/96 10:12 AM
     .
     .
     .
I think that the waveform problems are inherent in the very simple circuit 
design.  In testing the LFO in actual CV use, I found that it is really 
difficult to 'hear' the 'imperfect' waveforms.
     
The LFO range seems to be about .2Hz to 800Hz or so.  I'm planning to try 
changing the timing cap and rate pot values along with a range switch to get 
into lower frequencies.  If I get this working well, I'll post this and a 
couple of other mods on the home page when they are done.
     




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