Hi Takis,
The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 for each
voice respectivly. And Yes they are the same 2.2uF 50V Make sure they
are 50V rating. and correct polarity (You probobly knew that)
But before you replace those, try this.You are saying you are having
problems with all the voices right?
This points to the main DAC/Tuming circuit as you have already
guessed.
I would look closely at:
U811 The DAC
U816,U805 Multiplexer 4051
U812,U815,U813 Op Amps TLO81,TLO84,TLO81
U814 Analog Switch 4053
Any of these parts failing could cause tuning problems like you
describe.
Now, before you replace them carfully pull them from the sockets and
re-seat them. Sometimes corrosion on the socket/chip lead can cause
a "not to good" connection. Also before I replaced them I would
reflow the solder on the bottom of the board, as bad solder joints
could also cause this.
If this does not work replace em. All except the DAC are readily
available. I would wait till you replaced the other chips before you
went searching for this DAC to see if any others are the cause. If
one of the chips have failed, I would bet on the mux or analog switch.
It would not hurt to replace the capacitors I mentioned above, as
they are probobly on their way out anyway.
Let Me Know How It Goes
Karl
--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@...> wrote:
Hi Carl,
yes I replaced all six Cx49 capacitors!
What number are the other ones you're refering to?Are they also
2.2uF?
Many thanks,Takis.
--- In xpantastic@..., "Karl" <shire03@> wrote:
Hello takisdamaschis,
When you say output capacitors, are you talking about the small
2.2uF
Cx49 at the edge of the voice board? There is one for each voice.
There is also one of these at the output of each VCO feeding the
VCF
If these go you can have tuning problems. Also, try resetting the
software.( hold sown clear and turn power On)
Karl
--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:
Hi everyone, my xpander seems to fail the VCO tune test
randomly!some
voices fail during one test and pass on the next! there is no
cosistancy on the voices that fail,it can be any one of them!
Some
times(rarely) the vco test passes! I have the same problem
sometimes
with the Resonance and VCF but not as often!
I have totally rebuilt the power supply,changed the battery and
output
bypass capacitors!All currents measure right so this is not a
voltage
supply problem!
The only other part I can think of is the DAC or maybe the
Timer?
Any thoughts?
Takis.
