[sdiy] 4069 vco gives v+ noise?

[Scott Gravenhorst]

The 50 Hz (it looks like you are in Europe) and comments about
additional load makes one suspicious of the power supply.  The supply
I am using is a cheesey home built wallwart transformer, half wave
rectifiers with 78xx and 79xx regulators.  An opamp based triangle
LFO and this VCO should not draw even close to the maximum current
for those parts.  Problem with ground?  Have you looked at the supply
with a scope?

Power supply gurus?



=?iso-8859-1?q?Karl=20Ekdahl?= <_nial_ at yahoo.com> wrote:
>I use the same pinning as in the schedule you sent but
>it's still giving noise (in the v+ line). The noise
>seems like a 50hz wave with some minor disturbances
>riding on it that seems to be the osciallating tone. 
>
>The minor noise can at high frequencies be eliminated
>trough adding a 10uF cap at the v+ line but I can't
>reduce the major noise (the probable 50hz) without
>putting a resistor inbetween ground and gnd pin on the
>4069. And that - as i said - makes the square out die.
>
>The odd thing is that the noise only occurs if i add
>more modules to the same powersupply, for example a
>ASM lfo. The powersupply should be able to drive both
>modules (at least i think so) without any
>distrubances. It's based aroun 78xx, 79xx and 6800uF
>caps and uses the standard layout found in most
>powersupplies.
>
>/Karl
>
> --- Scott Gravenhorst <music.maker at gte.net> skrev: >
>René and I discovered that there is a sensitivity to
>> which inverters
>> are used for what purposes.  I found two
>> configurations that did not
>> work correctly.  When I hooked mine up like René's,
>> it began to work
>> properly.  I didn't notice noise on ground, rather,
>> I had a burst of
>> grass occuring on the PWM output when it should have
>> been a single
>> solid edge.  René was able to reproduce what I saw
>> by hooking it up
>> my "wrong" way.  Your problem might be related.
>> 
>>
>http://home1.gte.net/res0658s/fatman/VCO_pwm_tri_suboctave.html
>> 
>> See the center portion of the schematic with heavier
>> lines.
>> 
>> This is a linear version of the same VCO showing the
>> pinning that
>> works.  The one I built works very nicely.
>> 
>> 
>> =?iso-8859-1?q?Karl=20Ekdahl?= <_nial_ at yahoo.com>
>> wrote:
>> >Hello everyone, i've built René Schmitz 4069 vco
>> and
>> >stand alone it's working perfectly. But while
>> adding a
>> >few modules to the same powersupply the ground line
>> >starts "wobbling". 
>> >
>> >Through my limited electronics knowledge i've
>> >recognized that if i put a 100k resistor inbetween
>> >ground and gnd pin on the 4069 i can reduce the
>> noise
>> >but then the square out stops functioning. 
>> >
>> >Does anyone have any idea on why there's ground
>> noise
>> >and how to prevent it?
>> >
>> >thanks
>> >
>> >/Karl
>> >

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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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