Xpantastic!

Sag from an electrolytic going out on that voice?

James

> On Nov 28, 2018, at 5:01 PM, David Cumming david.cumming@... [xpantastic] <xpantastic@yahoogroups.com> wrote:
> 
> Hi,
> 
> My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas?
> 
> Thanks in advance, David
>

I would just change all of them for that channel. 

James

> On Nov 28, 2018, at 6:54 PM, David Cumming david.cumming@... [xpantastic] <xpantastic@yahoogroups.com> wrote:
> 
> Yeah I guess so. My soldering skills could stretch to replacing a few capacitors but I’m not exactly sure how to decide which.
> 
> I use a multimeter to find ones near the CEM 3374 that don’t hold charge compared to ones on a working voice board? 
> 
>> On Wed, 28 Nov 2018 at 23:52, 'James R. Coplin' james@... [xpantastic] <xpantastic@yahoogroups.com> wrote:
>>  
>> Sag from an electrolytic going out on that voice?
>> 
>> James
>> 
>>> On Nov 28, 2018, at 5:01 PM, David Cumming david.cumming@... [xpantastic] <xpantastic@yahoogroups.com> wrote:
>>> 
>>>  
>>> Hi,
>>> 
>>> My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas?
>>> 
>>> Thanks in advance, David
>> 
> 
>

I 'd change not only all capacitors, but the whole XPander and move to another neighborhood - just to make sure.

Change all capacitors, is not a good advice to a laymen. It can do more much more damage than the defect currently observed.

My advice would be to put more effort into locating the defect first, than just start some tedious solder work. IMHO the capacitor swapping thing is very fashy but often to no avail. Capacitors may break indeed, but no as often as indicated in these nice forums here. In fact, in the way over hundred of 80ies synths I had to repair, the capacitors only rarely had a problem.

I've seen lots of broken CMOS (40XX- and 45XX-type), OP-Amps (TL-type) and even resistors and ceramic capacitors (I've never read in a thread to change resistors or ceramic capacitors, but, yes the tend to break, in particular in California made Synths ;-)

I also note that electrolytics of that era are of much better quality as the material sold today. Why would you swap a electronic element, known to last more than 50 years, for a new part calculated be clever engineers to last ten years at most.

There are weak points in the Xpander VoiceBoard though:

the CMOS ICs and

the Styroflex S/H-charge capacitors.

Those components weren't build so well those days and tend to break quite often, that is, to become short, open or some state of random switching in between (funny).

Soldering of Styroflex caps is difficult and requires some experience. The must not get hot! There is no need to use Styroflex type again. You may use modern cap types here.

With you tunig problem, I'd first try to locate the tuning circuit in the schematics (or ask s.o. here) and then change/swap only t the parts for that functional instance. I'd start swapping the CMOS, then checking the S/H caps there, then the OP-Amps involved, then the electrolytics there.

Soldering of Styroflex caps is difficult and requires some experience. The must not get hot! There is no need to use Styroflex type again. You may use modern cap types here.

Hello David,        I've helped quite a few people fix their Xpanders/ matrix 12 over the years ( look in the history of this forum). I have never seen the Poly S/H caps fail.  The caps used  in the American made Matrix 12/ Xpanders are military grade and poly caps tend to repair themselves anyway. This is good news because you can't get audio poly caps anymore. ( when analog equalizers ceased being manufactured the relevant companies stopped making them)  I agree with other posters that the CMOS 4051 chips used to demux the control voltages to the voice circuits can fail. These would be  U706  and U707 for voice one on the xpander.  A relatively easy fix because all the chips are socketed on these synths. Which brings up another point. Over time chips can come loose in their sockets. If it were me I would ( carefully ) pull all the chips for the voice one circuit and push them back in ( re-seat them) this is also an easy fix.  You can use a chip puller or a small straight edge screwdriver can also be used.You may also try replacing C749 and C747. These are 2.2 uF   (note the decimal point) electrolytic capacitors. While not directly related to the tuning of the synth the are the most common failure by far on this particular synth.

 Best Luck Karl Schmeer 

   

 On Wednesday, November 28, 2018 5:22 PM, "David Cumming david.cumming@... [xpantastic]" <xpantastic@yahoogroups.com> wrote:
 

     Hi,
My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas?
Thanks in advance, David  #yiv5068428598 -- #yiv5068428598ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv5068428598 #yiv5068428598ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv5068428598 #yiv5068428598ygrp-mkp #yiv5068428598hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv5068428598 #yiv5068428598ygrp-mkp #yiv5068428598ads {margin-bottom:10px;}#yiv5068428598 #yiv5068428598ygrp-mkp .yiv5068428598ad {padding:0 0;}#yiv5068428598 #yiv5068428598ygrp-mkp .yiv5068428598ad p {margin:0;}#yiv5068428598 #yiv5068428598ygrp-mkp .yiv5068428598ad a {color:#0000ff;text-decoration:none;}#yiv5068428598 #yiv5068428598ygrp-sponsor #yiv5068428598ygrp-lc {font-family:Arial;}#yiv5068428598 #yiv5068428598ygrp-sponsor #yiv5068428598ygrp-lc #yiv5068428598hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv5068428598 #yiv5068428598ygrp-sponsor #yiv5068428598ygrp-lc .yiv5068428598ad {margin-bottom:10px;padding:0 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Hello Karl !

I received your email days ago and replied.
Again,- after some days I got the mailer demon "mail delivery failed 
..., permanent error".
Unfortunately you\ufffdre the only one I cannot send emails and it happens 
since Yahoo changed something.
In the attachement you\ufffdll find the note according to mail delivery error.
Maybe you\ufffdre able to contact your provider and fix it.

I keep it short here \ufffdcause I don\ufffdt think it\ufffds the place discussing our 
private stuff.
So, take it as some emergency notification via Xpantastic \ufffdcause I don\ufffdt 
see any other way contacting you a.t.m..

thx

PeWe

Hello there!
I just bought a Xpander but the voices are all messy .. the tune test fails on every voices and there is no bass sound. The notes are the same below C3... vcf is OK but I don't know how to test the DAC..😕

Hi

Frequently, fails like this are caused by open coupling caps at the output of each voice.  Part # would be Cx49 on the voice board a 2.2 uF electrolytic.

Look in the resources on this site  for an Xpander service manual. I think there is a simple DAC testing routine you can access from 
the Xpander's service page. 

- Karl

--------------------------------------------
On Wed, 5/8/19, pa7500@... [xpantastic] <xpantastic@yahoogroups.com> wrote:

 Subject: [xpantastic] Re: Xpander tuning issue
 To: xpantastic@yahoogroups.com
 Date: Wednesday, May 8, 2019, 4:17 PM
 
 
   
       
       
       Hello there!
 
 I just bought a Xpander but the voices are all messy .. the
 tune test fails on every voices and there is no bass sound.
 The notes are the same below C3... vcf is OK but I don't
 know how to test the DAC..😕
 
     
      
 
     
     
 
 
 
 #yiv0851312447 #yiv0851312447 --