[sdiy] SCI Pro One 15+ power rail

[Tom Wiltshire]

Olav is right to question the Mode and Repeat/Ext switches. My Pro-One has some dodgy switch contacts, and if these switches don't close properly, it's easy to get the synth in an unplayable state. I occasionally have to waggle mine back and forth a time or two.

I also second his analysis of "probably not the DAC". To say the DAC is at fault from those symptoms is a hell of a leap. It could be any of the VCA, the Gate circuitry, the envelopes, the output, the oscillators, etc etc. You need to narrow that down a lot more.

T.

On 28 Aug 2013, at 23:34, Olav Martin Kvern <okvern at ix.netcom.com> wrote:

> Hi Csaba,
> 
> re: "...still no sound with the keyboard played or from the CV/Gate [...] Not sure what the problem is but I'm suspecting the DAC"
> 
> If you don't get anything using CV/Gate from the external inputs, the DAC is probably not the problem. I'm hoping that's good news. When you have the middle Mode switch set to Repeat/Ext and provide a gate through the Gate input, does it trigger the envelope generators? Does the Gate LED in that section light up?
> 
> If (at some later point) you do find that there's something wrong with the DAC, the AD558 is still in production (according to www.analog.com).
> 
> Great synth--mine is still working fine. I walked miles through orchards in 1983 to pick up my tech manual from the SCI office. I'm sure the orchards disappeared long ago.
> 
> Thanks,
> 
> Ole
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