Hello, just finished building the Bi N Tic filter/ osc. and I have a couple of questions.
I was getting quite a bit of slop on the Frequency panel control. It basically only worked from about 12:00 on...
I traced this down to the 100n cap between pin 6 of the 3140 and the 100k that is connected to the base of the BC547`(of the collector is connected to the CD4024).
What was happening is that once the VCO went below a certain frequency, the Saw wave would all but disappear AFTER the 100n cap. It was a good signal at pin 6 of the 3140. The collect of the BC547 was just setting at 7V when the frequency was set to (or beyond) this low point.
I was able to rectify the situation (I think) by bridging the 100n. With the 100n out of circuit I get good strong oscillations for the entire range of the Freqency Panel control. The filter sonds really cool.
Any insight as to what might be happening would be greatly appreciate. I do not like the idea of removing something from the circit design in order to get it to work.
Thanx,
Tony
_________________________________________________________________
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I was getting quite a bit of slop on the Frequency panel control. It basically only worked from about 12:00 on...
I traced this down to the 100n cap between pin 6 of the 3140 and the 100k that is connected to the base of the BC547`(of the collector is connected to the CD4024).
What was happening is that once the VCO went below a certain frequency, the Saw wave would all but disappear AFTER the 100n cap. It was a good signal at pin 6 of the 3140. The collect of the BC547 was just setting at 7V when the frequency was set to (or beyond) this low point.
I was able to rectify the situation (I think) by bridging the 100n. With the 100n out of circuit I get good strong oscillations for the entire range of the Freqency Panel control. The filter sonds really cool.
Any insight as to what might be happening would be greatly appreciate. I do not like the idea of removing something from the circit design in order to get it to work.
Thanx,
Tony
_________________________________________________________________
Help yourself to FREE treats served up daily at the Messenger Café. Stop by today.
http://www.cafemessenger.com/info/info_sweetstuff2.html?ocid=TXT_TAGLM_OctWLtagline