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Subject: FW: [AH] Jupiter-6 Service Question!

From: "Verschut, Ricardo" <ricardo.verschut@...>
Date: 2000-06-02

-----Original Message-----
From: Scott Fiorenz [mailto:sfiorenz@...]
Sent: Thursday, June 01, 2000 4:03 AM
To: Analogue Heaven
Subject: Re: [AH] Jupiter-6 Service Question!

hello Kevin

> >Any idea what could be causing this? It does
> >the same thing on upper & lower boards with
> >the lower board being more noticable.
> >Not specific to one particular oscillator.
> >also,
> >The bleedthru noise is louder in unison mode
> >on the lower voice board (voices 1-4)..
> >and is only heard whenever a key is pressed,
> >not constant.. hmmmm..

Kevin Lightner wrote:
> A bad cap possibly? (They commonly make tons of noise in bad MKS80's)

Which cap might this be on the OB8? Any one in particular?
Just curious. I know there are some s&h caps on the voice
cards. Might that be the problem?
Nothing appears obviously blown on any circuit boards.
Is there some way to tell aside from measuring with
scope/dvm or are these abs. necessary?

> Have you disabled the noise source internally or used a dual trace
> scope to compare the raw noise source with the output noise?
> You need to verify it's not the noise source bleeding somewhere.

Yes, the nose has been disabled from the front panel. That seems fine.
oscs 1&2 bleed through both outputs even when off on front panel...
This isnt continous. Only happen when keys are pressed.
You can faintly hear the oscs when keys are played as well as
the hiss in the background, even with 1&2 + noise OFF..!
so somethings leaking (for lack of a better, more technical term..)
them through , which suxx.

> Have you set a scope to AC and checked the power supply rails at high
> scope gain?

no i dont have a scope yet unfortunately. Hope to soon though.
Open to suggestions for an accurate one that's relatively
inexpensive (under $1k). Besides, even if i had one i
wouldnt know how to do this ;) eheheheh!

> The noise may be on the DC rails either from a bad power supply or
> another component elsewhere.

So this would start @ power supply and leak all the way through
to output? im not certain what the dc rails are exactly.
R these something that is to be measured & calibrated on
the power supply? Sorry for the stoopiD questions..

> Problems like these are "divide and conquer" type probs. Isolate
> sections as best you can to eliminate them as the source and home in.

Yes i wish i was more experienced with the electronics end. Still
learning, its an ongoing process. I appreciate the suggestions
though! This is cool. Ill have something to tell the tech @
repair shop when i take it in. I ∗do∗ know how to play the
'football fight' theme from flash grodon soundtrck ;-) lol
YIPIEEEE!! "forget it ming -dales with ME" - - -
got the identical sound (the resonant bass & lead deal)
dialed up on the OB-Xa & saved as split preset. wow!
its pretty neat actually,
next one on the list to nail down is the 'batman' theme
or perhaps
"cHiPs" #o) heheheh what an epic ;)
maybe i can get a job on a cruise ship or something,
playing these over&over&over again repeatedly all day

> A few tips anyways. :)
> K

hey, thanks! Every little bit helps. Much appreciated.
Take care,

"hmmm.. why doesn't this magnet pick up the floppy disk?"..