About the boards swaping between the two M12, I thought about it, but since the other one is ok, it may be nice to kept this one safe no ;-) If you try to swap the board, you may change board ID in order to have two different one. You can only use one of the two first straps position.
Kris
Le 10 juil. 2012 à 22:34, Terje Winther a écrit :
Hi Omar,
Good point!I have been working on it for two full days now, so I am probably a bit bewildered. I will let it rest for a day, get back to it and hopefully discover something the day after tomorrow.The idea about the jumpers seems like a good place to re-start the debugging. I can reconfigre them and see if there is any change.TerjeDen 10. juli. 2012 kl. 17.17 skrev Omar:your goal is to rule out whether you have a bad board so that you're not wasting time thinking about or attempting to troubleshoot other areas outside of the voiceboards themselves. that's all im saying :)
once you know that you have two good boards, then you can narrow down your focus on areas other than the boards. if you have a bad board, then you can narrow down your focus on the bad board.
but until then, there's no point getting into details until you at least determine that.
-oOn Tue, Jul 10, 2012 at 10:56 AM, Terje Winther <terje.winther@...> wrote:
> at this point its a process of elimination,Yes, this is what I am trying to do.
> working backwards from a known operational
> point and ruling out all factors along the way.
There is sound from both voice cards. All 12 voices sound well, and
after tuning one card is perfect, while the other one is almost in
tune, but not quite. Some VCOs are off by a few notes, and some VCFs
are audible different, but not much.
With the scope I can follow all the sound paths, and I can follow the
sound path of the tuning. All good.
I have also followed all the digital control lines to see what they
are doing, and they all seem to come through.
I have swapped a lot of ICs between the voice cards, one by one,
checking to see if there is any change. Still no change.
It seems to me to be a systematic error somewhere that eludes me.
There is a network of 6 sets of DACs around UX06 and UX07, leading
through a resistor network to UX08 before going to the VCOs, VCF and
VCA, but there is one set of these for each individual voice, and I
find it hard to believe the the CV control for all voices would fail
at the same time. But it is interesting, because the PW and Resonance
passes tuning each time, and they uses another DAC (U816) that is
common for all the 6 voices on the voice card.
But as I now have swapped all the ICs in the critical positions
between the card to no avail, I am not sure what to do next. I could
shift the position of the ID strap. How many possible position are
there for that thing? (It is really just a jumper).
BTW: some of the ICs gets fairly hot. I have noticed that in other
Oberheim synths as well (almost burned myself on a OB-8 once). Is that
normal? I have checked power many times, so all power supply voltages,
frequencies and reference internal voltages are correct, and so far I
have found no short circuits. But still: they are somewhat hot.