[sdiy] Finally - after almost 2 weeks of tuning problems .......

harrybissell harrybissell at prodigy.net
Mon Jan 9 00:17:01 CET 2006

Is the 6.9 always stable ?  Its possible you are pulling too much
current so you are on the edge of regulation. If this is the case...
the resistor feedign the LM329 is now too small.

This is the 'hidden weenie' of all shunt regulators.


H^) harry

"Rykhaard D.A.M.I.A.N." wrote:
> Heh.  Minor, new problem. :P  Haha. :D
> I've got all 4 of the rotary switches hooked up again.  I ran into a
> small problem.  Whilst all 4 of them cycling away are sounding great -
> together they're about 99.5% in tune with each other.  :(
> One thought that I had, was to add a trimmer resistor, just before the
> 1K resistor to Ground.
> I tried a 200 ohm 20 turn trimmer, with an 820 ohm resistor replacing
> the 1K.  Nope.  Almost, but not quite.
> I tried a 500 ohm 20 turn trimmer, thinking that it would help me get
> that little bit of extra range.  Nope.  I finally realized that the
> extra resistance that I'm putting in, is acting JUST like a TUNING
> pot! :O  The frequency ratio is still the SAME right across.  There
> was no difference in tuning between the 1st and 12th position on the
> rotary, whether I had 820 ohms at the bottom, or 820 + 500 ohms at the
> bottom.
> Ahhhh!  So TUNING, WILL work on this version!  :D
> But now - how, do I get the ratio set exactly?  My only thoughts so
> far, are 0.1% each of the 1% resistors, around each rotary.  I THINK,
> that should take care of it.  Giving an even division between each
> step on the rotary.  No?
> Also - my trouble COULD be - not having tuned the 1V/octave trimmer in
> the Constant Current Source - EXACTLY.  (I'd rushed, on the 1st rotary
> set up.)  I'm going to go back, and trim it to beat free on 1 trimmer
> for the 1st and 12th positions, and see where that takes me. :)
> Another new trouble - using the LM329 6.9V reference with the Constant
> Current Source - is dropping my main output voltage to 1.6V. :O :O
> That only allows me enough resistance to drop the source 1 more volt.
> (Unless I go into -V.  Can I, without troubles??)
> I'm wondering if I should move up to a 10V source.  (Which I don't
> have anything FOR, at the moment - unless I can do the same thing as
> the LM329 with an LM723, variable regulator.)
> Anyhoo ..... I'm still pleased as punch. :)  Once I have my new maple
> panels in, I'll be mounting the PCB to it - and completing the
> sequencer, finally.  I don't wish to mount it to my prototyping
> pegboard, as I'll just have to rip it all out again, to move into the
> Maple panel. :(  And with the sequencer; 7 bit divider; S&H; white
> noise and 2 logic gates on this board - it'll be a LOT to transfer. :P
> Come on maple - hurry up and get here!  :D  LOL
> --
> Take care,
> Warmth and Peace,
> Ryk
> http://deathlehem.bravehost.com/damian.html - D.A.M.I.A.N .;s webpage
> - Jan. 0406 update

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