[sdiy] MG-1 revisited, LM337 issues

[Metrophage]

--- Bob Weigel <sounddoctorin at imt.net> wrote:

> Count your blessings.

I certainly do. Not everything in my life is crazy!

> Anyway yes assume you know where to see if you pot is adjusting
> the bias voltage for the regulator.  If that's moving the output
isn't
> then pretty much you have a failed regulator

I know how to check the trimmer resistance, but not the bias voltage.
Oh, I guess the resistance is what would be setting the bias voltage,
since it's the only pin where anything changes. So between the trimmer
and the adjustment pin, there should be the changing bias voltage?

> provided the voltage coming into it is above the needed headroom. 

Yes, 36vct for +12/-15v, that should be fine.

> You don't have a scope I take it?  

No, I don't. I never find any around here. New ones are too expensive
for me, and old ones are too heavy to order through the mail. Someday.

> Would be nice to know if there's a lot of ripple too.  Ripple can
> play various tricks on your meter.  Check for AC voltage with it if
you
> dont' have a scope.

Heck, gremlins and butterflies in Indonesia play tricks on this meter.
I am definately going to get a decent meter fairly soon. Sooner than a
scope. I will check for AC, I completely did not think of that. Would
the ripple be from the regulator? We'll see!

Thanks for the advice, Bob

CJ


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