Vintage Simmons Drums (UK) Users Group

Hi group, I recently became the owner of an SDS9 and like
many owners found it to have a few issues. A few of them I
have rectified already ie broken pots, replaced dud nicad
memory battery etc. The unit is from the US and as such has
a 115Vac power supply input. I am currently using a 230 to 115
volt step down transformer to power the unit but would like to 
convert the unit to plug straight into the local supply of 230Vac.

I have a nice copy of the schematics and I am an Electronics
Tech by profession. With the unit open, I see that the toroid
power supply transformer has the incoming 115Vac connected to
a pink and a brown wire via a 2Amp fuse and the main switch.
The tranny appears to be a common unit suitable for use at both
115 and 220/230Vac. I have come to this conclusion as there are
3 unused wires, Orange, Black and White which are left unconnected
but "capped off" with clear heat shrink insulation. It is my
guess that these are for use when 220/230Vac is supplied.
Obviously I could be completely wrong but it would be nice to 
confirm my thoughts from someone who has an SDS9 used at 220/230Vac.

Is there anyone on the group with a "euro" version who can confirm
my guess? Also I have noticed that the transformer looks quite
small considering it is protected by a 2Amp fuse. When operating,
it gets really warm, almost too warm for my liking.

The unit has a few other problems, such as intermittent triggering
of channels. I have so far confirmed by bench testing that the actual
channels are functional and that the triggering problem is occuring
due to an issue either in the CV multiplexing circuitry or the CV
D to A conversion section. I am going to remove the OS eprom and 
read the code out of it, disassemble the binary data and analyze
its function. I will then write up a faq on everything I discover
on my "journey" to return the unit to its full fuctionality so as to
aid others in keeping theirs in correct operation. I hope to include
a fault flow chart and rectification diagram to aid in sorting problems. I have had over 30 yrs experience in synth repair and
reverse engineering so this all should be do-able.

Sorry for the long post but I'd rather do some research than just dive in and dig a bigger "hole" to fill.

All help would be gratefully received

cheers

Richard

Ok, here are the voltages of the primary coil and their colours: 240V = orange, 220V = pink, 110V = white, 100V is brown. The other side is the black one.
Have a nice weekend.

[Non-text portions of this message have been removed]

I forgot: Replace the fuse by 1A type.

[Non-text portions of this message have been removed]

Thanks Michael for the info. It  is as I thought. Interesting tho
in the unit I have that they have chosen to connect the primary voltage
between pink 220V and brown 100v. This would give a differential of 120v which at 115v would give a slight undervoltage at the secondaries.
and thus increase the tranny current slightly.

Using the white 110v and Black 0v as u suggest would have been a better
choice. The Secondary voltage would be a tiny bit higher but it wouldn't be a big deal as the voltage regulators would have handled this fine.

If anyone is after technical help on things , please ask away as I am happy to help on any electronic questions and will do my best to answer them

Thanks again

Richard

--- In Simmons_Drums@yahoogroups.com, "Michael Buchner" <buchnerelectronics@...> wrote:

>
> I forgot: Replace the fuse by 1A type.
> 
> [Non-text portions of this message have been removed]
>

Hi Richard

I'm a newbie top this forum, but I just bought an SDS9, thats in bad need of repair. I found a local repairshop, that will do it, but if I bring a schematics the repair wil have a much greater chance of succes. In your original post you write that you have the schemaitcs. Would you mind posting this in the files section of this group? Or share it with me in some other way? It would be greatly appreciated.

Regards

Thomas

--- In Simmons_Drums@yahoogroups.com, "jabathaslut" <warlandr@...> wrote:

>
> Thanks Michael for the info. It  is as I thought. Interesting tho
> in the unit I have that they have chosen to connect the primary voltage
> between pink 220V and brown 100v. This would give a differential of 120v which at 115v would give a slight undervoltage at the secondaries.
> and thus increase the tranny current slightly.
> 
> Using the white 110v and Black 0v as u suggest would have been a better
> choice. The Secondary voltage would be a tiny bit higher but it wouldn't be a big deal as the voltage regulators would have handled this fine.
> 
> If anyone is after technical help on things , please ask away as I am happy to help on any electronic questions and will do my best to answer them
> 
> Thanks again
> 
> Richard
> 
> --- In Simmons_Drums@yahoogroups.com, "Michael Buchner" <buchnerelectronics@> wrote:
> >
> > I forgot: Replace the fuse by 1A type.
> > 
> > [Non-text portions of this message have been removed]
> >
>