[sdiy] Jupiter 6 troubles

[Jeff Farr]

Excellent, that you all for replying.  Testing the LS04 by grounding
pin 1 shows no response on any other pins.. I'll have to double check
that the IC is getting power but I don't think that is the problem.

On 7/1/07, Bob Weigel <sounddoctorin at imt.net> wrote:
> How's the DAC output?  -Bob
>
> Jeff Farr wrote:
>
> > I've got a JP6 here for who the lights are on, but nobody seems to be
> > home.  All the buttons on the panel boards light up but don't respond
> > to being pressed.  A quick look through the service manual and I
> > believe that there are 3 things to check for:
> > - The timer circuit is working properly
> > - The main uC (8031) is functioning
> > - The PROM is functioning
> >
> > Now, I've never scoped the output of a crystal oscillator and the JP6
> > uses one peirce oscillator buffered by inverters for the main uC and
> > two slave uC's.  You can see the schematic here:
> > http://www.asymetrik.org/Jupiter6_PierceOSC.bmp
> >
> > Probing around I can see an oscillation of about +-6mV at the right
> > frequency for the crystal.  However, it appears biased at about 400mV
> > on pins 1, 2, 3, 6 and 8 and about 800mV on pin 10 (output to the main
> > uC).  Now, I'll admit I don't know exactly what is inside the uC and
> > exactly how the inverters should be operating in this situation but I
> > wouldn't want DC present in my clock signal without some blocking
> > caps..
> >
> > Now.  If it turns out that this circuit is actually working properly,
> > but the PROM was dead, is there a way to test that the uC is working?
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