Hi Terje,
--- On Sun, 2/28/10, Terje Winther <terje.winther@wintherstormer.no> wrote:
>From: Terje Winther <terje.winther@...>
>Subject: Re: [xpantastic] Xpanding my horizon
>To: xpantastic@yahoogroups.com
>Date: Sunday, February 28, 2010, 9:16 AM
>Hi all, and thanks for all the input regarding the Matrix-12 repair
>that I am doing.
>The unit is in very good shape and sounds good. Among other things all
>the displays are fine, panel is good, wooden sides are in fine shape,
>and all keys (except one broken) looks good.
>There are some trouble manuvering the synth, as several buttons don´t
>respond. It was kind of dirty before I started working on it, so I
>guess several of the buttons needs to be cleaned, as I had to do with
>they keys (both keytops and key contacts).
Good idea, you also might swing out the displays ( board is hinged ) and clean the
glass of the VFD's as well as the front panel bezel. It can really spiff it up.
>I have run across some various interesting failures:
>- One voice is dead, and I have pinpointed this to the fact that the
>VCA output (leg no. 14) of the CEM3372 is dead. All else on the chips
>works as it should; inputs, VCF sections and all. It is just the VCA
>that is gone. Usually when a CEM chip fails it is completely dead, so
>this was a puzzle for me. Swapping chips with other voices turns it
>into a working voice. So a new chip is needed here, then.
You can still find those.
>- The rotary encoders all work, thankfully. It is just the Schmidt
>trigger chips that seems to mailfunction, just as Karl Schmeer
>suggested (thanks!). If I rotate the encoder with a very specific
>speed - slowly, but not too slowly - I can make it increase somewhat,
>but it is difficult. Reducing with the same encoder is no problem.
>Need new chips probably, or maybe just clean up?
Thanx
That is exactly the symptom I had. I thought the encoaders were dirty but a little checking with a scope
revealed a distoted output of the trigger chip.
I used 74HC14 chip. You can get them for cheap.
I Changed out U6 and U13 on the potentiometer board. Its faster than taking the
encoaders apart and cleaning them but you may have to do this anyway.
> Then the real problems:
> - Only voices 1-6 can be heard. Internally all voices (both 1-6 and
> 7-12) seems to work fine (I can scope it all). This might be connected
Question: when you say unresponsive, I imagine you mean the voices can not be heard,
but what about the little green dots on the display? There are dots that show which
voices are being played on the Programmer display. Do these not light up?
> to the next problem...
> - The "Voices 1-6 / Voices 7-12" button is unresponsive, so I have no
> way to see if the second voice board is turned off or not. Are there
> any workaround for this?
You may know this already but, That button is only active in multi mode.
The buttons are just momentary push buttons. You could solder another pushbutton ( Normally open)
in it's place, on the bottom of the board with long extension wires.
This would be a temporary fix, just so you can access voices 7 - 12.
I can think of a some reasons the upper voices (7 - 12) would not play:
I am going on the assumption that all voices are set to the same patch.
A patch could have a VCA mod by a footswitch residing in voices 7 - 12, causing them to be mute.
1) Voices 7 - 12 turned off in master page.
2) Voices 7 - 12 Pan setting to off. ( in the master page)
> - Unresponsive buttons. How do you usually solve this? Clean them, or
> change them? It seems to me that there are standard momentary buttons
> underneath the large black front panel buttons.
I have had some luck with cleaning them but replacement is better. They used to be readily available,
but not so much anymore. I need to replace some of mine, to tell you the truth but
still need to find a modern part number.
Anyone?
>The power supply have a fairly high physical hum, so at one point it
>probably needs to be changed. The internal power is stable, but a
>little bit off spec, like +12.1 and -11.82. Is this to much off? I
>hope not, because that means I have to rebuild the whole power, with
>new regulator transistors and all.
I have seen the transformer cause hum like this. It is not failed, the metal plates of the transformer have come loose
and vibrate with the line frequency. There is no fix short of replacing the transformer.
The voltages sound close enough to be OK. If you scope it and there is no appreciable ripple < 50 mv
the power supply is probobly OK.
BTW It might not be a bad idea to the power supply. The electrolytic caps in the power supply get the most abuse, And are the most likly thing to fail "in anything electronic".
Best Luck
Karl Schmeer
