[sdiy] Roland SH 101 tuning

Antonio Tuzzi antoniotuzzi at gmail.com
Thu Dec 9 10:04:19 CET 2010


Hello friends,

I'm trying to tune this sh101 (is not the first time I do an sh101 tuning )

and something strange is happening:

when I go in TEST mode 
and I try to do the D/A calibration

1)
when I move the VR2 (D/A TUNE), the closer I can get is  -22~25  mV  against the 0V   (+-1mV) wanted

2)
the test mode on D/A Width with VR1
gives 2.50 against 2.75

3)
test mode on D/A lienarity
gives 2.33 against 2.5

tension coming out from the transformer circuit are vey stable 

and the circuit gives back  +5v     and -5V  without  ripple



MORE

playing notes are oscillating with a random pattern, oscillation are in the order of cents

the oscillation is visible on the CV out to

the tuning is unstable when use the sequencer too (detaching the keys)

If I use the resonance as generator

I'm getting the same tuning problem

so must be something NOISY in the "CV" path


Any idea?

thanks

Antonio







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