Analogue systems

HI,

I think I've a problem with my RS integrator, and I think it's coming
from the power supply...
The Vco dont seems to be stable, like all the others part in fact, the
vcf and co, all are "like detuned" or make a very long oscillation...
I can find where is the fault... thus i supposed it's the power supply...

When I check the value, I have 
for the normaly 12v out, a value from 20.4v to 20.5v
for the 5v, it's ok, 5v are coming out
for the -12v, i obtain from -14.8v to -15v...

Is it normal?
Does someone have the same value?

I've replace all the composant (except the transfo) by new ones, but
nothing change...

Any advice, solution, are welcome!

thx!