EMS Synthi A Problem

jun at h-und-p.de jun at h-und-p.de
Mon Dec 15 10:03:35 CET 1997

Dear List,

once again I want to bore you with my sick EMS. After having my A board checked
by someone who owns a VCS3 and getting told I should try and exchange the
rectifier I'm still having the same problem: on the -9V tree of the power
supply there is a ripple that causes an annoying sound on everything. Especially
on filter and VCOs this causes a modulation that is very  recognizable.
Some observations that I made: I am not able to adjust the negative branch
to -9V when there is only Board A plugged in, it is always something like
-10,3 V. On both branches there is aripple in triangle form which has the
same value on the scope. Unfortunately this scope is so old an completely
deadjusted, that it only works as a visualizer of waveforms. So I can't
measure this value exactly. When I plug in boards B and C, the ripple on
the +12V branch diminuishes. The one on the -9V not, it just changes the form,
becoming a rounded triangle. I'm suspecting now a defect in the transfomer but
I am totally insecure, as I am not an EE (I got this scope for free, in case
you're wondering). Hints, comments and suggestions for new powersupplies
are highly welcome. Thanks for your patience. 

Desparately yours


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