Ang: Re: [sdiy] oxford OSCar: anyone familiar with these?

[Gavin & Delia]

----------
>From: "Daniel Araya" <daniel.araya at sr.se>
>To: <elmystico at earthlink.net>
>Subject: Re: Ang: Re: [sdiy] oxford OSCar: anyone familiar with these?
>Date: Wed, Sep 17, 2003, 12:04 PM
>
>Hmmm...maybe I dont get this right, but isn't the OSC1 & 2 signals
>derived from the DA-converter in the upper middle of schematic page 3,
>converted from current to voltage by ic25 and some resistors and then
>multiplexed and sampled/hold by ic 26, 27 and ic28 and then run into the
>filter?

I realize I may have misunderstood the schematic page 2, the data lines
running through the RS FF (IC 38)  that go into those twin 4046's that are
labeled as having an internal VCO.  I assumed those were the sources for the
OSC signals.  The top one has a complete set of data.  the bottom one is
missing some data lines, particularly the one at pin 3, but now I'm
realizing that these are not the signal sources as I though they were, or
are they?


>Do you have any signal at the various outputs in the osc2 chain (ic26
>pin 5, ic28 pin 14, ic27 pin 3 & ic28 pin8)? 

None, anywhere.  All the way back to the DAC, that's why I was beginning to
think it was programming.  As far as I remember (Monday was the last I
looked at it)  there was a - voltage offset where the OSC2 signal should
come out, the 4053 looked like it was bad, but it wasn't, the multiplexing
was working but there was no signal.  So on the switch for OSC2 you would
see the high frequency timing on the control pin and the common, but just
get a DC voltage at the place where the waveform should be.  Looked exactly
like a blown 4053 gate, but i replaced it and it is the same...

>I would check the voltage at OSC2-volume output of ic31 pin 15 and ic30
>pin 8.

I'll do that and report back.

>
>Let me know how it goes. If all else fails I might pop the lid on mine
>and pke around a bit.

Thanks!