[sdiy] EMS VCS3 II negative power supply problems

Magnus Danielson magnus at rubidium.se
Fri Sep 16 21:57:17 CEST 2022


Check the buffer transistor. That had blown on mine.

The Mark II PSU is nicer than the Mark I PSU for VCS3/Synthi-A.

About the same time as the Mark I and Mark II shift, they moved the 
transistors off the PSU board. If they are on the board, move them out 
as this remove heat and it will eventually fail. Guess how I know.


On 2022-09-13 21:50, Mattias Rickardsson wrote:
> Hey,
> I'm trying to revive a VCS3 II where the power supply has issues on 
> the negative regulation. With an incoming -25 V it puts out roughly 
> -24 V instead of the supposed -9 V. Does anyone have experience with 
> similar problems?
> (The transformer was fried on the negative half, so I'm running it 
> from a bench supply. I have also replaced the regulating 741 and 
> TIP3055 power transistor)
> ((The phutney.com <http://phutney.com> site and its very readable 
> schematics also magically disappeared, which didn't help)) :-)
> Best,
> /mr
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