----- Original Message -----From: chris_i_rollandSent: Wednesday, February 15, 2012 9:21 AMSubject: [Ensoniq-VFX-SD] Re: Crapulence / Audio Output / Power Supply?
--- In Ensoniq-VFX-SD@yahoogroups.com, Rish wrote:
>
> Try replacing all the diodes on the power supply board, it sounds like they are dying off.
>
> Rish
>
> Life is like MIDI, your either IN, OUT or THRU.
>
>
> On Feb 14, 2012, at 1:17 PM, "chris_i_rolland" <;chris_i_rolland@...> wrote:
>
> > So reading through a lot of the threads here I see a number of possible posts related to what I have, but am not sure exactly which is most relevant if at all.
> >
> > I have had my VFX from ages past, and have updated EPROMS, changed batteries, fixed the keyboard and done all the things we have to do to keep these babies alive. However recently I have had a problem that I can't put my finger on. When I turn on the VFX all is well, however after a while (and it could be 30 minutes, or it could be a couple of days - yes I said days), a couple of things happen. Firstly on the audio output I lose almost all of the left channel, at this point I sometimes (but not always immediately) start getting what others have decscribed as "crapulence", but this is very dependant on the patch. Or actually it is dependant on the Effects in use, and it tends to be only on the release of a note . . . Rebooting the keyboard does NOT fix the issue, but leaving it unplugged for some time does (and that can also vary between leaving it for a few hours to days/weeks).
> >
> > Frankly I am tempted to get another VFX should I ever see one on eBay/Gumtree (or a VFX-SD or maybe an SD-1 if they are patch compatable), but really I'd like to fix this venerable old workhorse. I have skills in soldering and electronics, but don;t have the detailed diagnostic skills to work out exactly what is going wrong, which is why I went through the threads, and see comments on Bias adjustment, or the Power Supply, but somehow I suspect there are multiple issues running in here, which is why I hope the collective pool of wisdom can assist here . . . all suggestions gratefully received.
> >
> > Chris.
> >
> >
>
Two votes for power . . . I did have the full circuit diagrams, so will trawl through the studio to look for them as I mislaid them a while ago, and replace the diodes as a start . . . can replacement Power supply boards be gotten hold of easily if it is something more than diodes/capacitors?
Message
Re: [Ensoniq-VFX-SD] Re: Crapulence / Audio Output / Power Supply?
2012-02-15 by jammie
no but just change the caps diodes rarely go and if
they do the go with a bang
you would know if the diode blow as they shatter in
half and can blow holes in the pcb but this is usually due to reverse voltage
being higher than the diode can take
the glass rectifier diodes used in the psu are over
sized for heat dissipation so would not fail
they are linear psu,s and just rely on bridge
rectifers for dc
then smoothing caps to smooth the semi ac voltage
into a pure rippless dc line which then go to power regulators for regulated dc
lines
they are the most common type of psu but are not
energy efficient
but the good thing is the most common problem with
them is heat on the caps 85oc not so bad for most european countries as they
dont get hot weather but in the states and humid countries of asia the ambient
tems are high and so the working temps are higher the 85oc caps that they
used
;
had a low life at 85oc extremes and so when they
get hot they expand and start to lose there ability to hold charge so when they
discharge there signal is week eventually they stop all ripple all together from
the bridge circuit which looks
like camel humps on a scope the more caps put in
parallel to earth the smoother the dc lines
ensoniq used large caps for this
im an ex ensoniq authorized repair tech from the uk
and have been fixing these synths for over 20+ years
i work on components level
the ensoniq synths are well designed and the psu is
the most common fualt of there synths
all there psu designs are i dentical in there
topology
this is so they could use the same parts for all
ther designs and the psu is made from off the shelf components so are easily
repaired
the d4+ uses rubbish computer motherboard caps with
a life of only 2000 use at 85oc
i have had to change 100 caps on these boards as
they just fail cuasing al types of problems the biggest is dc blocking in the ac
audio meaning getting 15vdc on the 3.3v audio circuits
now other manufacturers used switchmode psu
the korg m1 t1 o1w use this type of device and they
use italian transformers which you can buy anymor and they
burn out i have had to make linear supplies to
replace these so that i could carry on using these machine as linear
is easy to do and only require a very few
components