[sdiy] 4046 VCO

Jay Schwichtenberg jschwich53 at comcast.net
Fri Jul 6 02:26:13 CEST 2018

Well I don't have the time so can't help with that one.


It'd help to have all the details and schematic to know how you've changed the circuit though. I would guess that the expo would need to be tweaked to get the expo current right.


And as said there are some brands of 4046s that work better than others as far as range and tuning in the original circuit.


Good luck.

Jay S


From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Pete Hartman
Sent: Thursday, July 05, 2018 5:09 PM
To: Tim Ressel
Cc: synth-diy at synth-diy.org DIY
Subject: Re: [sdiy] 4046 VCO


If the whole circuit is running on 5V?  Probably.  it's designed for 15V, and can work with 12V with a little bit of component modification.

I'd be willing to bet that the charge time on the cap at 5V would be a lot faster than at 15V :-D




On Thu, Jul 5, 2018 at 6:58 PM, Tim Ressel <timr at circuitabbey.com> wrote:

I'm running mine on 5 volts. also an issue?

On 7/5/2018 4:47 PM, Jay Schwichtenberg wrote:

I'd say using a 5V part in a 15V circuit might be a problem.

Also look on Muff's. There are particular brands of the 15V parts that work
and others that don't work well.

Jay S.

-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Tim
Sent: Thursday, July 05, 2018 4:20 PM
Subject: [sdiy] 4046 VCO


So I built up a Thomas Henry 4046 VCO and ran into an issue: the
frequency out is way too high, starting at 55KHz and going up to 175KHz.
I checked my schematic and it all looks good except for one thing; I am
using a 74HC4046 instead of a CD4046. Is that causing my problem?

--Tim Ressel
Circuit Abbey
timr at circuitabbey.com

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