Just theorizing here: could a faulty cap across one of the lines cause swings in voltage?
Recently I shuffled some units around, pulled the 960 out of the system and put it back. I've noticed that now the + voltage takes an eternity to settle after powering up. It will swing up to 15.6v and then drift randomly between that and 14.8v for maybe 15 minutes before finally settling on 14.9, while the - voltage heads right to -14.9 and stays there, rock-solid. I've had a meter hooked up for the last few days trying to figure out the pattern.
I'm inclined to say that the problem isn't due to the PSU, which is a dotcom NOS by Power One, because my dotcom VCO doesn't drift in pitch at all but the two MOTM vcos do,
together, and along with the + voltage. The 960 is the only thing between the PSU and the MOTM units, so it's the only thing that appears wonky.
Matthew
On 23-Nov-09, at 8:19 PM, Paul Schreiber wrote:
a) technically, they are not 'bypass' caps, they are 'bulk' caps. A 'bypass' cap is a small value cap (like 0.01uf) that is very close to an IC's power pin. It is there to 'bypass' RF frequencies to ground cause by the lead inductance of the part. The caps used in the '960 are there to reduce voltage drop when wiring large cabinets, where the '960 is say 20-30" away from the main supply (or if you are wiring say 2-4 of them up in a big cabinet.
b) the caps are across the +-15V lines, so every connector "sees" the caps.
Both bypass caps and bulk caps are needed in 'real systems' to counter effects of the 'real world'.
Paul S.
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