Xpantastic!

Hi Terje,

Wow Two M12's :-)

The version of the M12 service manual I have " Bought from Factory long ago" is 
pretty thin on details. 

It's just schematics and a few engineering change orders.
If you have not done so check out the Xpander Service manual. It's in the files 
section of this group.
The calibration procedures for the trimmers you speak of  are in there, as well 
as a detailed 

description of what really goes on during the auto tuning routine.

You probably already checked these things but just to be sure:
Do the 2.2uF caps that were replaced have a 50VDC rating? If not they will not 
pass the audio signal correctly. 

Actually "the entire board failing tune "points to a more systemic failure. 
Both the VCO and VCF are tuned the same way with the exception that the VCF's 
resonance
 is set to oscillate.  A specific voltage is applied to the individual VCO or 
VCF
and the output  frequency is monitored by the CPU to allow tuning.


I would start at the DAC circuit ( page 19 xpander service)  There is a trimmer 
in that circuit for 

DAC offset calibration. ( The procedure is at the end of the Xpander service 
manual page 34.
Maybe thats all that is wrong :-) 

If not :
There is also a procedure for checking the board reference voltage ( page 34) If 
this voltage is off spec it could 
cause errors. 
Try swaping  DAC's between the "known good board" and your failed one. Or any 
other parts in the DAC circuit.

There is a circuit on page 31 (Lower right hand corner in Xpander service)  
Which is used in the auto tuning routine. It is built around an LM311 voltage 
comparator 

which ties to the output of  each voice. 
Something may be amiss here.

Report back after these checks and I will think about it some more.

Best Luck

Karl
 


________________________________
From: Terje Winther <terje.winther@...>
To: xpantastic@yahoogroups.com
Sent: Fri, July 6, 2012 12:30:38 PM
Subject: [xpantastic] only one board active

  
Hi all,
Thanks a lot for all the help I have been given on this list. I have 
changed parts in the power supply, some CEM chips, all those el.caps 
who blocked tuning and sound, swapped some 74 series logic chips (so 
now all encoders works), and got new switches and rubber feet, and 
even a new key. And of course cleaned it up since all boards were out 
anyway.
The Matrix-12 is almost all right now - it is just one peculiar error 
left:
It seems that only one of the voice cards gets the proper commands.
Voice 7 - 12 fails tuning of VCOs and VCFs, but all other tuning 
passes and there is sound from all 12 voices (if I turn them on) and 
the voices are almost in tune, and VCFs seems to work like they should.
I also have another Matrix-12 in for service (yes, two M-12s in front 
of me - pretty sight!), and it too reportedly have an issue with only 
one of the voice cards working properly.
I have double-checked the connectors (the paralell connector and the 
two 3-4 pin connectors) and they all seems to be fine.
Any tips on what to do if one of the voice cards don´t responds?

On another question: While having all the boards out, I noticed that 
there are very few manual trimmers on the M-12, but there are some, 
and I can´t seem to find any info on how to calibrate them. I have the 
service manual, and I find the trimmers there, so I can pretty much 
guess what to do, but it would be nice to know for sure.

Terje Winther
terje.winther@wintherstormer.no
http://www.wintherstormer.no/