kirkdegiorgio wrote:
has a second PCBA with the all the bells and whistles on it.
The PCO uses a self-heated 3046 in the expo converter circuit. I would
suspect pot problems (although doubtful as I believe you've said they were
all recently replaced, yes?) or the 3046 not heating up as two possible
culprits. Much like what Analogue System does now on their filter and VCO,
in that all the trannies on the 3046 are on the same substrate, Serge used
segments of it as a heater to get the whole chip up above room temp for
compensation - much like the UA726 did by design (this was the equiv part
used in early Moog mini's and Buchlas, which consisted of a matched NPN pair
and a heater).
Another suspect could be the PSU. Are you running close to its capacity?
As daft as this sounds - is the PCO off to the end of the line of VCOs or
are there stable NTO's flanking it? If it's off to one end, is it furthest
away or closest to the end of the panel where the power is coming in from
the PSU?
- Peter
> but although the PCO no longerWeird - the PCO and NTO engines are identical. Same board. The NTO just
> warbles all over the place it does drift significantly more than the
> NTO/PCO's on my other panels ( it drifted flat 1 whole semitone
> over a week - whilst the other NTO/PCO's were still accurate during
> the same period)
has a second PCBA with the all the bells and whistles on it.
The PCO uses a self-heated 3046 in the expo converter circuit. I would
suspect pot problems (although doubtful as I believe you've said they were
all recently replaced, yes?) or the 3046 not heating up as two possible
culprits. Much like what Analogue System does now on their filter and VCO,
in that all the trannies on the 3046 are on the same substrate, Serge used
segments of it as a heater to get the whole chip up above room temp for
compensation - much like the UA726 did by design (this was the equiv part
used in early Moog mini's and Buchlas, which consisted of a matched NPN pair
and a heater).
Another suspect could be the PSU. Are you running close to its capacity?
As daft as this sounds - is the PCO off to the end of the line of VCOs or
are there stable NTO's flanking it? If it's off to one end, is it furthest
away or closest to the end of the panel where the power is coming in from
the PSU?
- Peter