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Xpander skipping voice / voice fail

[email protected]
 

Hi all,


so I discovered this week that Voice 4 on my Xpander has died and is skipping when playing.


I don't believe its a dead voice chip as I switched the chips and couldn't replicate the issue on the switched voice channel.


Both OSC and PW are failing the auto tune.


So from the research i've studied online I could also try the following:


Replace the?capacitor at C449 as this seems to be a common capacitor that dies.

This would be a?2.2 uF?polarized electrolytic capacitor?with?a 50 VDC rating.


And then recap further caps on that voice and the power supply.

(I'm pretty sure that the power supply was recapped by a tech a couple of years ago though)


I could also try replacing the D4051BC chips on that voice.


I'm ok with a soldering iron but not by any means a qualified tech so I want to make sure i'm buying the correct capacitors, a local store sells this product:




Would that be ok to use to replace the?C449?capacitor? It seems like its the correct voltage and value but it doesn't say if its?polarized. Also how many of these should I buy if I need to start replacing other?capacitors on the voice channel?


any advice greatly appreciated?


D.
 

Hi,

Yes, you are correct. That cap tends to fail.? I bought a hundred of them
some time back, but have?only had to replace?2 or 3 of them, over the years.?
The part in your link should work?fine.?

One thing you might consider, capacitors fail over time, so...?
Look for a cap with a high mtbf? (mean time before fail)?rating.
Just because it's my M12 I found the highest mtbf possible.
Check digi-key.com

Best Luck

Karl
?
?
[email protected]
 

ok many thanks, i'll start by swapping the C449 cap and see how I get on.
[email protected]
 

So I finally had time to look into this, it didn't fix the problem.

Also I sadly made things worse when soldering the new caps in place.

i've managed to lift off a trace line from the board from too much solder heat, the line in question is the one that goes from the C449 cap to some resistors in a section called U108. I think I can fix it by using a loop technique to reattach some wire but i'm not sure what resistor that trace line goes to.

Of course I could take out the resistors in U108 but i'm trying to avoid that, any one know what one the C449 trace line goes to?

Its either - R186, RR183, R182, R181, R180, R179, R178.
 

?


>On Monday, February 20, 2017 4:43 PM, "dfoster.graphics@... [xpantastic]" wrote:


?
>So I finally had time to look into this, it didn't fix the problem.

>Also I sadly made things worse when soldering the new caps in place.

>i've managed to lift off a trace line from the board from too much solder heat, the line in question is the one that goes from the C449 cap to some resistors in a section called U108. I think I can fix it by using a loop technique to >reattach some wire but i'm not sure what resistor that trace line goes to.

>Of course I could take out the resistors in U108 but i'm trying to avoid that, any one know what one the C449 trace line goes to?

>Its either - R186, RR183, R182, R181, R180, R179, R178.


The cap C449 is the output signal from voice 4 to the panning and auto calibration circuits
It should feed?four ( 4 )?networks:

On Positive side of cap +
????????1????Goes?from the output of opamp U416? ( pin 6)?
??????? 2?? Goes to feedback resistor for opamp R470

On negative side of cap -
??????? 2?? Calibration circuit,? input resistor? R181
????????3?? Multiplexer chip U105?? (pin 3 ) ?on the main control board????????

After repairs you can check theses nets with an ohmmeter.

Using an?electronic ?solder with more flux ?may be helpful.

Hope This Helps
Karl

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