Xpantastic!

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:

http://www.jaycar.com.au/2-2uf-50vdc-low-leakage-electrolytic-capacitor/p/RL6420

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

>On Monday, February 20, 2017 4:43 PM, "dfoster.graphics@yahoo.com.au [xpantastic]" <xpantastic@yahoogroups.com> 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 circuitsIt 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