Hi Christian,
Yes,
I find it useful when people post their results as well and wish others
did it more often, so hopefully my update will be of use to
someone.
Regarding
your Matrix 1000, looking at some info on the internet, I think the Matrix 6R & Matrix 1000 have different power supplies. But sadly I am not really experienced enough with electronics to recommend
whether you update your PSU or not, so perhaps some fellow readers with
more knowledge can advise you.
I know the Matrix 1000 came out several years later than the Matrix 6R and according to the following website was produced between 1987-94, see http://www.vintagesynth.com/oberheim/mat1000.php
Whereas Matrix 6 & 6R were produced from 1986 - 1988. So if your Matrix 1000 is from the later end of production, it may still be ok for some time before worrying about PSU upgrade.
However I did find an interesting link that might be of use, and certainly worth a read.
But
if you do decide to upgrade, make sure you have all the information
before hand. I learned a valuable lesson today about exactly that,
regarding my attempt to update the front panel tact switches on my
Matrix 6R, which I posted about on this group earlier and now need to
update as well.