Archive of the former Yahoo!Groups mailing list: 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