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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.

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.

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.

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.

Wow Karl,
are you sure you haven't designed this synth?
You definately have amazing knowledge on it's design!
I will replace all parts you mentioned except for the DAC wich I will
at least reseat!
In return for your help let me know if you're ever in dire need of a
fluorescent display for your own use ofcourse!
I was smart enough about 10 years ago to buy a couple NOC ones spare
just in case and I know they are impossible to find!
I'll let you know how it goes!
Thanks,Takis!

Hi Karl,
I have gone and replaced all parts you suggested, re-seated the dac
and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins of U815 instead of
4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac ($150) which I will try
out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.

Hi Takis,

I also noticed that I get 3.79V at one of the pins of U815 instead
of 4.0V(+/- .05V) as the service manual points out!

Okay, lets look at D805, A zener diode which provides the reference
for the DAC.Measure this with a good voltmeter, it should be 6.9V.
Again, try reflowing the solder around this part and the ref circuit.
If you have a service
manual, Look at the circuit around U815 and reflow all the solder
around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@...> wrote:

Hi Karl,
I have gone and replaced all parts you suggested, re-seated the dac
and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins of U815 instead

of

4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac ($150) which I will

try

out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@..., "Karl" <shire03@> wrote:

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.

--- In xpantastic@..., "Karl" <shire03@...> wrote:

Hi Karl,
done everything you pointed out,no improvements!
Anything else you can think of before we go for the DAC?
Thanks,Takis.

Hi Takis,

I also noticed that I get 3.79V at one of the pins of U815 instead
of 4.0V(+/- .05V) as the service manual points out!

Okay, lets look at D805, A zener diode which provides the reference
for the DAC.Measure this with a good voltmeter, it should be 6.9V.
Again, try reflowing the solder around this part and the ref circuit.
If you have a service
manual, Look at the circuit around U815 and reflow all the solder
around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
I have gone and replaced all parts you suggested, re-seated the dac
and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins of U815 instead

of

4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac ($150) which I will

try

out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@..., "Karl" <shire03@> wrote:

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.

Hi Takis,

What does the your voltmeter read when you measure the zener(D805)?
I keep thinking it's something to do with this circuit.
I am going to open mine up and see what I get.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@...> wrote:

--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Karl,
done everything you pointed out,no improvements!
Anything else you can think of before we go for the DAC?
Thanks,Takis.

Hi Takis,

I also noticed that I get 3.79V at one of the pins of U815

instead

of 4.0V(+/- .05V) as the service manual points out!

Okay, lets look at D805, A zener diode which provides the

reference

for the DAC.Measure this with a good voltmeter, it should be

6.9V.

Again, try reflowing the solder around this part and the ref

circuit.

If you have a service
manual, Look at the circuit around U815 and reflow all the solder
around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
I have gone and replaced all parts you suggested, re-seated the

dac

and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins of U815

instead

of

4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac ($150) which I

will

try

out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@..., "Karl" <shire03@> wrote:

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.

Hi Karl,
the voltmeter reads 6.38v!
Takis.

Hi,
are you talking about the D805 diode?
If so, mine does not have a capacitor parallel to it!
Did yours have one all along? If so please let me know of it's specs
so that I can add one myself!
Thanks!


--- In xpantastic@..., "bjorn roland" <bjorn.roland@...>
wrote:

Tip...
A zener diode is always "noisy". It generates ripples in the voltage.
Ripples in referance voltage may cause autotune to fail.
To avoid these ripples there is always a capacitor mounted in

paralell to

the zener
to flatten out these ripples. Check ac voltage also, not only dc.
Ac will show ripples. Should be zero, but if not check out this

capacitor.

On Thu, Oct 2, 2008 at 5:02 PM, Tony Cappellini <cappy2112@...> wrote:

Hello Takis

Where did you make the measurement?
This sounds somewhat like the reading I got- when I measured one

of the

diodes near the battery. (as directed in the service manual test

procedure)

On Thu, Oct 2, 2008 at 1:12 AM, takisdamaschis

<takisdamaschis@...>wrote:

Hi Karl,
the voltmeter reads 6.38v!

Takis.

--- In xpantastic@... <xpantastic%40yahoogroups.com>,

"Karl"

<shire03@> wrote:

Hi Takis,

What does the your voltmeter read when you measure the zener(D805)?
I keep thinking it's something to do with this circuit.
I am going to open mine up and see what I get.

Karl



--- In xpantastic@... <xpantastic%40yahoogroups.com>,

"takisdamaschis"

<takisdamaschis@> wrote:

--- In xpantastic@... <xpantastic%40yahoogroups.com>,

"Karl" <shire03@> wrote:

Hi Karl,
done everything you pointed out,no improvements!
Anything else you can think of before we go for the DAC?
Thanks,Takis.

Hi Takis,

I also noticed that I get 3.79V at one of the pins of U815

instead

of 4.0V(+/- .05V) as the service manual points out!

Okay, lets look at D805, A zener diode which provides the

reference

for the DAC.Measure this with a good voltmeter, it should be

6.9V.

Again, try reflowing the solder around this part and the ref

circuit.

If you have a service
manual, Look at the circuit around U815 and reflow all the

solder

around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@...

<xpantastic%40yahoogroups.com>,

"takisdamaschis"

<takisdamaschis@> wrote:

Hi Karl,
I have gone and replaced all parts you suggested,

re-seated the

dac

and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins of U815

instead

of

4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac ($150) which I

will

try

out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@...

<xpantastic%40yahoogroups.com>,

"Karl" <shire03@> wrote:

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@...<xpantastic%40yahoogroups.com>,

"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@...<xpantastic%40yahoogroups.com>,

"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@...<xpantastic%40yahoogroups.com>,

"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.

Hi Takis,
I measured the D805 in mine: 6.95 Vdc. I notice it's a diode in a
transistor package. This is a very accurate reference diode. It
should read at least 6.9 Volts. Pin 1 is not used. I measured from
The left side of R856 ( just below it) to the middle leg of the
diode. My schematics identify this as a 6.9 V Zener. If the one in
yours shows a lower voltage than that, maybe this is causing the
tuning errors. The diode may not be bad, something maybe dragging it
down. I would take U815 out (turn Off first), then measure it again.
If you can't get 6.9V out of that ref, I would replace it.
BTW about where is the adjustment trimmer pointing?

Karl




--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@...> wrote:

Hi Karl,
the voltmeter reads 6.38v!
Takis.

--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Takis,

What does the your voltmeter read when you measure the zener

(D805)?

I keep thinking it's something to do with this circuit.
I am going to open mine up and see what I get.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Karl,
done everything you pointed out,no improvements!
Anything else you can think of before we go for the DAC?
Thanks,Takis.

Hi Takis,

I also noticed that I get 3.79V at one of the pins of U815

instead

of 4.0V(+/- .05V) as the service manual points out!

Okay, lets look at D805, A zener diode which provides the

reference

for the DAC.Measure this with a good voltmeter, it should be

6.9V.

Again, try reflowing the solder around this part and the ref

circuit.

If you have a service
manual, Look at the circuit around U815 and reflow all the

solder

around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
I have gone and replaced all parts you suggested, re-seated

the

dac

and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins of U815

instead

of

4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac ($150) which

I

will

try

out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@..., "Karl" <shire03@> wrote:

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.

Hi Tony,
I'm talking about D805 at the DAC circuit!



--- In xpantastic@..., "Tony Cappellini" <cappy2112@...>
wrote:

Hello Takis

Where did you make the measurement?
This sounds somewhat like the reading I got- when I measured one of the
diodes near the battery. (as directed in the service manual test

procedure)

On Thu, Oct 2, 2008 at 1:12 AM, takisdamaschis

<takisdamaschis@...>wrote:

Hi Karl,
the voltmeter reads 6.38v!

Takis.

--- In xpantastic@... <xpantastic%40yahoogroups.com>,

"Karl"

<shire03@> wrote:

Hi Takis,

What does the your voltmeter read when you measure the zener(D805)?
I keep thinking it's something to do with this circuit.
I am going to open mine up and see what I get.

Karl



--- In xpantastic@... <xpantastic%40yahoogroups.com>,

"takisdamaschis"

<takisdamaschis@> wrote:

--- In xpantastic@... <xpantastic%40yahoogroups.com>,

"Karl" <shire03@> wrote:

Hi Karl,
done everything you pointed out,no improvements!
Anything else you can think of before we go for the DAC?
Thanks,Takis.

Hi Takis,

I also noticed that I get 3.79V at one of the pins of U815

instead

of 4.0V(+/- .05V) as the service manual points out!

Okay, lets look at D805, A zener diode which provides the

reference

for the DAC.Measure this with a good voltmeter, it should be

6.9V.

Again, try reflowing the solder around this part and the ref

circuit.

If you have a service
manual, Look at the circuit around U815 and reflow all the

solder

around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@...

<xpantastic%40yahoogroups.com>,

"takisdamaschis"

<takisdamaschis@> wrote:

Hi Karl,
I have gone and replaced all parts you suggested,

re-seated the

dac

and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins of U815

instead

of

4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac ($150) which I

will

try

out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@...

<xpantastic%40yahoogroups.com>,

"Karl" <shire03@> wrote:

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@...

<xpantastic%40yahoogroups.com>,

"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@...<xpantastic%40yahoogroups.com>,

"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@...<xpantastic%40yahoogroups.com>,

"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.

Hi Karl,
I just got the new DAC! It's an HS3140C.I installed it
and.....nothing!Every test fails now instead of only some VCO's!
My original DAC is an MP7614KN, are these two incompatible and if so
why are they mentioned as both able to do the job?
Furtermore is there anything else I should have done when I replaced
the DAC that is not mentioned in the manual?
Thanks,Takis.

Hi Takis,
On page 34 of the Xpander service manual there is a DAC calibrtion
procedure. A different chip would need a calibration.
What about the reference voltage?

Karl





--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@...> wrote:

Hi Karl,
I just got the new DAC! It's an HS3140C.I installed it
and.....nothing!Every test fails now instead of only some VCO's!
My original DAC is an MP7614KN, are these two incompatible and if so
why are they mentioned as both able to do the job?
Furtermore is there anything else I should have done when I replaced
the DAC that is not mentioned in the manual?
Thanks,Takis.


--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Takis,
I measured the D805 in mine: 6.95 Vdc. I notice it's a diode in a
transistor package. This is a very accurate reference diode. It
should read at least 6.9 Volts. Pin 1 is not used. I measured

from

The left side of R856 ( just below it) to the middle leg of the
diode. My schematics identify this as a 6.9 V Zener. If the one

in

yours shows a lower voltage than that, maybe this is causing the
tuning errors. The diode may not be bad, something maybe

dragging it

down. I would take U815 out (turn Off first), then measure it

again.

If you can't get 6.9V out of that ref, I would replace it.
BTW about where is the adjustment trimmer pointing?

Karl




--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
the voltmeter reads 6.38v!
Takis.

--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Takis,

What does the your voltmeter read when you measure the zener

(D805)?

I keep thinking it's something to do with this circuit.
I am going to open mine up and see what I get.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Karl,
done everything you pointed out,no improvements!
Anything else you can think of before we go for the DAC?
Thanks,Takis.

Hi Takis,

I also noticed that I get 3.79V at one of the pins of

U815

instead

of 4.0V(+/- .05V) as the service manual points out!

Okay, lets look at D805, A zener diode which provides the

reference

for the DAC.Measure this with a good voltmeter, it should

be

6.9V.

Again, try reflowing the solder around this part and the

ref

circuit.

If you have a service
manual, Look at the circuit around U815 and reflow all

the

solder

around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
I have gone and replaced all parts you suggested, re-

seated

the

dac

and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins of

U815

instead

of

4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac ($150)

which

I

will

try

out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@..., "Karl" <shire03@>

wrote:

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.

Hi Karl,
I did the calibration procedure but unfortunately I can't get the DAC
trimmed down to 0volts!It keeps showing 4v(pin 6)!
Does that mean that the DAC is faulty?

Hi Takis,

Does that mean that the DAC is faulty?

Could Be, What happens if you put the old one back in, And check
it's calibration, from pin 6 of U815?

Karl


--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@...> wrote:

Hi Karl,
I did the calibration procedure but unfortunately I can't get the

DAC

trimmed down to 0volts!It keeps showing 4v(pin 6)!
Does that mean that the DAC is faulty?

--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Takis,
On page 34 of the Xpander service manual there is a DAC

calibrtion

procedure. A different chip would need a calibration.
What about the reference voltage?

Karl





--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
I just got the new DAC! It's an HS3140C.I installed it
and.....nothing!Every test fails now instead of only some VCO's!
My original DAC is an MP7614KN, are these two incompatible and

if so

why are they mentioned as both able to do the job?
Furtermore is there anything else I should have done when I

replaced

the DAC that is not mentioned in the manual?
Thanks,Takis.


--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Takis,
I measured the D805 in mine: 6.95 Vdc. I notice it's a diode

in a

transistor package. This is a very accurate reference diode.

It

should read at least 6.9 Volts. Pin 1 is not used. I measured

from

The left side of R856 ( just below it) to the middle leg of

the

diode. My schematics identify this as a 6.9 V Zener. If the

one

in

yours shows a lower voltage than that, maybe this is causing

the

tuning errors. The diode may not be bad, something maybe

dragging it

down. I would take U815 out (turn Off first), then measure it

again.

If you can't get 6.9V out of that ref, I would replace it.
BTW about where is the adjustment trimmer pointing?

Karl




--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
the voltmeter reads 6.38v!
Takis.

--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Takis,

What does the your voltmeter read when you measure the

zener

(D805)?

I keep thinking it's something to do with this circuit.
I am going to open mine up and see what I get.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

--- In xpantastic@..., "Karl" <shire03@>

wrote:

Hi Karl,
done everything you pointed out,no improvements!
Anything else you can think of before we go for the DAC?
Thanks,Takis.

Hi Takis,

I also noticed that I get 3.79V at one of the pins

of

U815

instead

of 4.0V(+/- .05V) as the service manual points out!

Okay, lets look at D805, A zener diode which provides

the

reference

for the DAC.Measure this with a good voltmeter, it

should

be

6.9V.

Again, try reflowing the solder around this part and

the

ref

circuit.

If you have a service
manual, Look at the circuit around U815 and reflow

all

the

solder

around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
I have gone and replaced all parts you suggested,

re-

seated

the

dac

and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins

of

U815

instead

of

4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac

($150)

which

I

will

try

out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@..., "Karl"

<shire03@>

wrote:

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.

Hi Takis,

My original DAC is an MP7614KN, are these two incompatible and
if so why are they mentioned as both able to do the job?

Looking at the data sheets These two parts( MP7614KN and HS3140C) are
the same, and should be interchangable. If you have an output of 4 V
on PIN 6 of the opamp(U815), then the op-amp could be at fault also.

Karl



--- In xpantastic@..., "Karl" <shire03@...> wrote:

Hi Takis,

Does that mean that the DAC is faulty?

Could Be, What happens if you put the old one back in, And check
it's calibration, from pin 6 of U815?

Karl


--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
I did the calibration procedure but unfortunately I can't get the

DAC

trimmed down to 0volts!It keeps showing 4v(pin 6)!
Does that mean that the DAC is faulty?

--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Takis,
On page 34 of the Xpander service manual there is a DAC

calibrtion

procedure. A different chip would need a calibration.
What about the reference voltage?

Karl





--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
I just got the new DAC! It's an HS3140C.I installed it
and.....nothing!Every test fails now instead of only some

VCO's!

My original DAC is an MP7614KN, are these two incompatible

and

if so

why are they mentioned as both able to do the job?
Furtermore is there anything else I should have done when I

replaced

the DAC that is not mentioned in the manual?
Thanks,Takis.


--- In xpantastic@..., "Karl" <shire03@> wrote:

Hi Takis,
I measured the D805 in mine: 6.95 Vdc. I notice it's a

diode

in a

transistor package. This is a very accurate reference

diode.

It

should read at least 6.9 Volts. Pin 1 is not used. I

measured

from

The left side of R856 ( just below it) to the middle leg of

the

diode. My schematics identify this as a 6.9 V Zener. If

the

one

in

yours shows a lower voltage than that, maybe this is

causing

the

tuning errors. The diode may not be bad, something maybe

dragging it

down. I would take U815 out (turn Off first), then measure

it

again.

If you can't get 6.9V out of that ref, I would replace it.
BTW about where is the adjustment trimmer pointing?

Karl




--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
the voltmeter reads 6.38v!
Takis.

--- In xpantastic@..., "Karl" <shire03@>

wrote:

Hi Takis,

What does the your voltmeter read when you measure the

zener

(D805)?

I keep thinking it's something to do with this circuit.
I am going to open mine up and see what I get.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

--- In xpantastic@..., "Karl" <shire03@>

wrote:

Hi Karl,
done everything you pointed out,no improvements!
Anything else you can think of before we go for the

DAC?

Thanks,Takis.

Hi Takis,

I also noticed that I get 3.79V at one of the

pins

of

U815

instead

of 4.0V(+/- .05V) as the service manual points

out!

Okay, lets look at D805, A zener diode which

provides

the

reference

for the DAC.Measure this with a good voltmeter, it

should

be

6.9V.

Again, try reflowing the solder around this part

and

the

ref

circuit.

If you have a service
manual, Look at the circuit around U815 and reflow

all

the

solder

around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@..., "takisdamaschis"
<takisdamaschis@> wrote:

Hi Karl,
I have gone and replaced all parts you suggested,

re-

seated

the

dac

and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the

pins

of

U815

instead

of

4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac

($150)

which

I

will

try

out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@..., "Karl"

<shire03@>

wrote:

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.