Elektor Formant Modular

Hi,
i finally got the old formant system repaired, and it run´s..
But from time to time the oscillators won´t "start". Means, if i 
switch off and on again, then sometimes the oscillators produces sound. 
But sometimes i need to do a retune on the "start" poti of the circuits.
Anyone else have this problem ? it´s very annoying when you don´t 
know if the system works, if you switch it on..
If i test one VCO alone, and the other two unplugged it always works.
But the psu is big enough ...

Kind regards
Wolfgang

Check the dynamic impedence of the psu, if one vco works allways on 
it's own, then that state's that there is an issue with the psu not 
delivering enough current on switch on.

There may be enough current when the system is on, but it is the 
initial powerup that is a problem. This could be caused by either 
wiring or not enough capacitance on the output of the psu, it may also 
be the output rail's not reaching full voltage quick enough, alot of 
companies use an inteligent switch on the output of their 
powersupplies, this switch is basically the same as the speaker 
disconnect switch on Hi-Fi amplifier's, it wont switch on until the 
psu voltage is stable.

rgds

Laurence

















--- In ElektorFormant@yahoogroups.com, "stecki2" <steckenleiter@T...> 
wrote:
> Hi,
> i finally got the old formant system repaired, and it run´s..
> But from time to time the oscillators won´t "start". Means, if i 
> switch off and on again, then sometimes the oscillators produces 
sound. 
> But sometimes i need to do a retune on the "start" poti of the 
circuits.
> Anyone else have this problem ? it´s very annoying when you don´t 
> know if the system works, if you switch it on..
> If i test one VCO alone, and the other two unplugged it always 
works.

> But the psu is big enough ...
> 
> Kind regards
> Wolfgang