[sdiy] Memorymoog acting strange

[Roy J. Tellason]

On Tuesday 14 March 2006 09:59 am, Chris Manders wrote:
> Hi Christian
>
> I don't know the Memorymoog, but the problem sounds
> very similar to the one I had with my Moog Source. It
> suffered from the 'Crazy Source' problem which was
> caused by oxidisation on the voltage regulators which
> are pushed into sockets on the circuit board.
>
> I removed the sockets and soldered the regulators
> directly down and the problem disappeared.
>
> If not this, perhaps another loose connection
> somewhere.
>
> Christian

Now that you mention it,  I do remember hearing about something of the sort,  
from Moog themselves...

Their initial production runs were having those parts soldered directly into 
the boards.  Then thermal stresses caused the leads to actually pull out of 
the parts.  Then they switched to the sockets,  and the same thermal stresses 
caused enough movement to take the plating off of the contacts in the 
sockets.  Their solution was to remove the sockets,  and to extend the 
component leads,  with that extension having an "S" curve to it,  so that it 
would take up the slack of those thermal stresses.  That should take care of 
the problem...

(I didn't tie the symptoms in the original post to this...)

> --- ChristianH <chris at chrismusic.de> wrote:
> > well, I know, they're almost all acting very
> > strange...
> >
> > Mine has developped something weird: it contiuously
> > sees pot movements,
> > even when completely left alone.
> > This is pretty nasty, since this will abort any
> > calibration menu,
> > and the display will jump to the changed pot values
> > instead. Most of the
> > time, I won't even get to the calibration menu at
> > all, because I can't
> > complete the "C" and number button sequences without
> > being struck by
> > some intervening pot change display.
> >
> > At first I suspected the 4051s on the panel boards
> > collecting the pot
> > voltages, but replacing those didn't change a thing.
> > Same with the 393
> > comparator on the DMUX board.
> > 10 V pot reference voltage is perfectly stable
> > within +/- 1 mV, both at
> > the DAC and after the buffer for pot supply.
> >
> > The programmable threshold circuits on the DMUX
> > board (IMHO not quite
> > correctly described as "hysteresis" in the technical
> > manual, real
> > hysteresis is only achieved in conjunction with
> > software operation)
> > appear to do their thing. If I manually activate
> > them one by one, the
> > MUX BUS voltage is increased or decreased by some 50
> > mV, as intended.
> >
> > If I completely remove the MUX BUS line, leaving the
> > CR2/CR3 junction
> > before the 393 comparator open, there are no changes
> > seen.
> > However, connecting the bus line to a single pot or
> > ground will show
> > continuous movement again (and that pretty much
> > precludes the simplest
> > cause, i.e. a shaky pot).
> >
> > Has anybody else ever seen behaviour like this?
> >
> > regards
> > Christian
> >
> > BTW, I can't remember having seen so much bad
> > mechanical engineering in
> > one device (well, apart from my own wild'n'careless
> > diy stuff I did at
> > the tender age of 16). The wiring is a mess, oodles
> > of cables going from
> > everywhere to everywhere. Accessing the DMUX board
> > (or even removing it...)
> > is a major pain in the you-know-where. Big fat
> > ground wires soldered
> > closely in between two ICs only 100 mil apart, so
> > you can hardly
> > unsolder them without burning the IC sockets. Add to
> > that lousy board
> > silk screening where you mostly can't tell "6" from
> > "8". Yuck.
> >
> > If only that goddam thing wouldn't have that
> > gorgeous sound ;-)
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin