[sdiy] asm1 lfo and power supply

[patchell]

Nils Pipenbrinck wrote:

> Hi There.
>
> Once again an asm-1 question. I have trouble getting the lfo to work. (shame
> on me, it's such a simple circuit). Is this circuit sensitive on a "not
> really good" power supply?
>
> To be honest I'm still working with a very bad powersupply built around a
> 7815 and 7915. Worse is, that I have -17V instead of -15 (don't ask me why -
> only the 7915 knows...).
>

    A lot of the 7915's floating around these days will not regulate unless
there is a load.  I just purchased a bunch of them that have this problem.
However, under load, they work just fine.  You did not mention if when you
measured the voltage if the -17 was open circuit or not.

    While 7815/7915 does not make the worlds greatest power supply, it does make
a very good power supply.

    If you haven't seen my power supply tips goto:
http://www.silcom.com/~patchell/powersupply/powersupply.html
    And
http://www.silcom.com/~patchell/synthmodules/powersupply.html

>
> I've read a lot of times, that a good power supply _is_ important. Mine is a
> pice of junk. It has ripple, it does the wrong power, it's noisy, and each
> time I'm, working with it remember that I'm just a mortal (you can touch the
> wires of the mains). But nevertheless - it did it's job for over a 5 years
> now. It supplied my guitar preamp. It supplied all my experimental
> diy-circuits, and it survived uncounted short circuits.
>
> Back to the LFO:
>
> I checked my pcb a couple of times, changed opamps, measured here and there,
> and everything looks fine. Could it really be my sucking power supply?,`Even
> if it's a pice of junk I never had serious problems with it.
>

    If you are talking about the ASM-1 LFO, it will work under almost any
conditions.  I know this doesn't help you much.  However, when I am trying to
debug something, I always start by eliminating problems one by one.  Since you
have identified a problem with the power supply, this is a good place to start.
Quite often, I will stumble across the real problem while eliminating all of the
others, even if I don't think they could be connected.

>
> Thanks in advance,
>
>         Nils Pipenbrinck

--
 -Jim
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