Analogue systems

Ladies Tangents,

I took delivery of a RS350 yesterday and was quick you work a 
little magic to it that I thought you may enjoy.  Works great.

One thing, as always - doing modifications to a module under 
warranty will effect that module's warranty.  Although this is an 
easy mod requiring no cut traces or added holes on the 
faceplate, unless you're really comfortable with a soldering iron, I 
wouldn't attempt this

The beauty of this is the module can be easily returned to stock 
in the event you wish to remove it - just hang on to the jack you're 
going to have to pull.

This consists of  replacing one of the two duplicate output jacks 
and adding a double pole on-off-on  switching its place to allow  
for three different slew ranges, from long to 'give me a break' 
long.

Admittedly, for those of you who do more keyboard type work, the 
stock 350 is just fine. But...any of you would like to convert an 
otherwise stepped  random sample and hold to a freeform slow 
wobbling line of random voltage, this is the ticket.

I have posted a schematic of this mod in the file section of this 
site,  It can also be seen here:

http://www.buzzclick-music.com/RS350_mod.jpg

DIRECTIONS:

THE RS350 CONTAINS A 4066 CMOS QUAD ANALOG SWITCH.  
BEAUSE OF THIS, YOU SHOULD WEAR A GROUNDED WRIST 
WRAP WHILE DOING THIS MODIFICATION.

1) Remove RS350 faceplate by unscrewing the nuts which hold 
on the jack and the pot.

2) Remove the bottom board mounted jack - SLEW OUT B.  As 
the traces and pads for  this are huge, there shouldn't be any 
problem doing this - no risk of lifting pads unless you use a torch

Once the solder it removed form the four terminals of this 
connector, simply lift the jack upward until its free form the 
assembly.

3) Remount the faceplate.

4) Mount a double pole, on-off-on switch to the location where  
this removed jack used to be.  This switch will have six terminals 
on the back - two rows of three (see the schematic for a detail 
drawing).  The switch is such that it will rest as well in the center 
position and can be thrown upward and downward.  Its case will 
fit PERFECTLY in the spot where this jack used to be.

5) Solder two wires form the existing leads of the 100nf cap to 
the switch center poles.  This is the only tricky part.  

5A - Turning the board over to the solder side, solder one wire to 
the TOP lead of the 100nf cap. This is point  'A' on the schematic. 
Be careful that any exposed wire does not come in contact with 
any other part of the assembly.  Route this wire down the 
solderside of the PCB and wrap it around to the top side at the 
bottom of the board. solder the other end of this wire to the LEFT 
center terminal of the switch when looking at the switch form the 
rear and oriented so that the narrow dimension is horizontal 
(again, see schematic)

5B - Again turning the board over to the solder side, solder the 
second wire to the BOTTOM lead of the 100nf cap. This is point  
'B' on the schematic. Be careful that any exposed wire does not 
come in contact with any other part of the assembly.  Again, route 
this wire down the solderside of the PCB and wrap it around to 
the top side at the bottom of the board. solder the other end of 
this wire to the RIGHT center terminal of the switch.

6) Solder the first cap across the two top 2 terminals of the cap 
as shown in the schematic diagram.  MAKE SURE THE 
POSITIVE LEAD FACES TOWARD THE LEFT SIDE WHEN 
VIEWING THE SWITCH FORM THE REAR (see schematic).  
Electrolytic caps are such that the body usually indicated the 
NEGATIVE lead.  Make sure this lead goes to the RIGHT end of 
the switch.

7) Solder the second cap across the bottom top 2 terminals of 
the cap as shown in the schematic diagram.  MAKE SURE THE 
POSITIVE LEAD FACES TOWARD THE LEFT SIDE WHEN 
VIEWING THE SWITCH FORM THE REAR (see schematic)

In both 6 and 7 above, make sure you locate these caps as to 
not interfere with the mounting of the module back into it's rack.  
Basically, if you make sure the don't hang over the edge of the 
bottom of the board, or stick up higher than the edge of the 
faceplate on the Z axis, you'll be fine.

USING THIS MODIFICATION:

You have now installed two caps which allow you to add 
capacitance to the charging that causes the slewing, making it 
longer than it would have been without this addition.

Start with the switch set to the middle position.  When it's set like 
this, your mod has no effect, the module will operate as it did 
before it was installed.  Flipping the switcheither upward or 
downward will engage the each  cap, which will have a 
noticeable effect on the amount of slew currently dialed in. One 
will be longer, the other, the 10uf, will be ridiculously long.

All other functions (ON/OFF, VC Slew, V OUT) will be unaffected 
by this mod, no matter which position is set in.  They will still 
operate perfectly.

enjoy and BE CAREFUL WHEN SOLDERING!!!!!

- P