Vintage Synth Repair

It has remained perfectly stable since the fix.  Are you having a
similar problem?

Thanks,
Stephen

--- In vintagesynthrepair@yahoogroups.com, "gil_we" <gil_we@...> wrote:
>
> Hi there.
> 
> Is your P5 still stable after the fix you describe here ?
> 
> Thanks!
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, "easterleggs" 
> <milotoll@> wrote:
> >
> > My Prophet 5 display flicker/lockup problem has been solved!  When
> > replacing the LM337 voltage regulator I noticed that the screw and 
> nut
> > that connects the regulator to the large heat sink would not tighten
> > beyond a certain point.  I thought it was snug enough and proceeded
> > with my power supply cap replacement.
> > 
> > Upon second inspection the threads of that screw had worn away so 
> the
> > LM337 regulator (negative supply) was not making good contact with 
> the
> > heat sink.  Following the recommendations of the service manual, I
> > replaced all three regulator screws with new #4 3/8" round head
> > machine screws.  I cleaned the heat sink, mica tabs and regulators 
> of
> > any old heat sink compound.  I reapplied heat sink compound to the
> > back of the regulators and to the mica tabs.  I fastened the
> > regulators to the heat sink using the nylon washers, lock washers 
> and
> > nut with new screw prepared with a blue, medium duty threadsealer
> > compound.  I tightened the screw until the nylon washer started to
> > deform.  
> > 
> > The Prophet 5 now does not exhibit the initial flicker/glitch noise
> > problem I had before changing ALL power supply caps NOR does it 
> jitter
> > and lockup after an initial 15-20 minute warm up.  Lesson learned:
> > Don't neglect the power supply in the Prophet 5!
> > 
> > Thanks for all the suggestions!
> > 
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "easterleggs"
> > <milotoll@> wrote:
> > >
> > > My Prophet 5 had an issue where the LED's would occasionally 
> flicker
> > > slightly and introduce a glitch noise into the audio output.  I've
> > > since replaced all  power supply caps (tantalums replaced with
> > > electrolytics) and the LM337 voltage regulator.  After some 
> initial
> > > tests it seems to have remedied the glitch noise problem (even 
> though
> > > the LED's will flicker a bit when adjusting the FILTER CUTOFF
> > > pot...?), BUT (isn't there always a 'but'?!) a new issue has
> > > manifested.  My Prophet is a rev 3.3 with MIDI.  When in preset 
> mode
> > > on any patch ending in the number 8, some LED's on unused buttons
> > > flicker on and off, the numbers on the panel will scramble a bit, 
> and
> > > occasionally, the synth will skip into TUNE mode.  The problem 
> doesn't
> > > happen when I press the PRESET button to take it to panel mode nor
> > > when the patch number ends in anything other than 8.  Is this a 
> RAM
> > > (6508 CMOS) problem?  Anyone dealt with this before?
> > >
> >
>