Ok y'all here's the modification you've all been waiting for. I spent most of last night writing the text, looking through the circuits of my SH-101 and drawing the illustrations, so this had better be good! Hallvard ROLAND SH-101 modulation/filter modification -------------------------------------------- This is a modification for the Roland SH-101 synthesizer that let's it have external control over filter and modulation. The synthesizer still works as normal after the modification, but when the jack plugs are used, the LFO and VCF are externally con- rollable. Two GIF pictures are enclosed at the end of the construction article which follows. The are "UUENCODED", so you have to cut them out of the rest of this text and type "uudecode filename..uu" and you will be able to use them as standard GIF files. The modification consists of the following components: 2 pieces 3.5mm jack sockets with break contact 1 piece 100K ohm resistor connecting wire (prefferably of differnt colour to avoid confu- sion) Other than that a soldering iron and solder is needed, and an electric drill with appropriate drill bit to fit the two jack sockets in the SH-101 case. (The jack sockets don't have to be fitted in the case, if you'd rather not cut in it). If you'd rather not, you could take the wires from the synth. and use a small plastic box to put the sockets in (although it would be much more practical to fit it in the synth casing). I fit mine on the left, top side of the synth, just next to the "modulation grip" sockets and above the "MODULATOR" writing. Then I used white "rub-on" letters (Decadry, Alfac etc.) to label the sockets with "MOD" and "VCF". It almost looks as though it was made like this from Roland! So, with a bit of work you could get a really good and nice result. PS PS When you drill the holes, be sure to look on the inside of the casing, so you don't hit the plastic "standoffs" or anything else that could be in the way! OK, let's move on... I have enclosed two GIF drawings, one for each modification. The pictures show which wires go where on the jack sockets and where to connect on the circuit boards. MODULATION (LFO) MODIFICATION: ------------------------------ 1) Open up the synth. by removing all the screws on the back of the unit. By removing the big, black metal plate you get access to all the electronics. Wow! Can these small plastic and metal things on those boards really give me that great sound- unbelievable!!! After having recovered from this enormous experience and admired the innards of the synth long enough you are ready to go on... 2) Put the synth on something soft so it won't get scratched up, front panel down, and keyboard end facing towards you. On the right lower side you see a circuit board where the pitch bender is located at the very bottom. 3) By looking at the GIF picture (illustration no.1), compare it with the circuit board you have in front of you. Find the traces marked off in the illustration. Be sure to get the right ones! It's better to be safe than sorry on this one, so take your time!!! No need to remove this circuit board. 4) The GROUND connection is the easiest to find. This is the big, wide circuit trace which goes all around the circuit, but the bottom end (the end where the pitch bender is) is a good reference and connection point. This is by the way a common GROUND connection for both the MODULATION and FILTER jack sockets. 5) If you are SURE that you have found the other trace, you are ready to cut it in two. Use a flat bladed knife ("Stanley" or similar- the types used to cut in linoleum and carpets). Be sure not to cut any other circuit traces. 6) You can now solder the appropriate wires to the appropriate points to the jack socket. It's a good idea to use different colours for the different connections, to avoid confusion. The GROUND wire can have the same colour as the GROUND wire for the FILTER socket. All in all there are three connections on the circuit board and three connections on the jack socket for the modulation socket. FILTER MODIFICATION ------------------- 1) Turn the synth around, so that the keyboard end goes away from you. 2) Now, at the end nearest you, you can see a big circuit board which is possibly labelled "SYNTH BOARD" (on the right hand side in my synth). This board has to be removed to get access to the board under- neath. 3) Remove the two multi-pin connectors on the bottom end (the two connectors that are closest to the end where you are). You do this by pulling them up carefully. 4) Remove all the screws on this board- be sure to remove ALL of them, some are hard to see at first glance... 5) Lift up the bottom end (the side closest to you) of the circuit board, and turn it over the keyboard side- this way you don't have to remove (and un-solder) all the multi-cables. 6) You now have access to the board where you are about to install the wires for the filter (VCF) socket. Look at the circuit board (you don't have to remove this board as the solder side is up! Try to find some writing on the board where it says "Key follow", VCF mod", "env mod" etc... These are the connection points for the VCF sliders on the other side. 7) Locate an 8 pin IC between "env mod" and "resonance". This is easily found as there are two rows of 4 soldering points which are arranged very neatly. 8) Find the 2nd pin from the top on the right hand side and con- nect a wire here. Be sure to have the synth the right way, and look at illustration no.2 so you are sure you have the right con- nection! 9) At the end of this wire: connect a 100K ohm resistor, and connect this to point no. 4 on the jack socket, as shown in the illustration. In other words: the resistor goes between the connection point on the circuit board and the jack socket. Be sure that the resistor doesn't touch any other point, either on the circuit board or the GROUND point of the socket! 10) Connect the GROUND wire from the jack socket to the same point as the GROUND of the modulation socket- i.e. the end of the small circuit board closest to the pitch bender (see illustrations). 11) Check all connections twice and check for bad connections etc. If everything is OK then you can put the black plastic sheet in place (which goes on top of the battery compartment to show the battery directions). Now you can fold the main circuit board back in place- careful not to damage any wires! Put all screws in place and check if anything is missing. Reassemble the back panel of the synth. That's it! Congratulations-You've just made you're SH-101 able to respond to external control for modulation/filter! Finally I have to say that I won't be held responsible for any sort of damage, accident etc. due to this modification. I have tried to be as accurate as possible, describing the modification. Although it's quite easy to do the modification itself, it's a little hard finding the correct circuit traces (especially the modulation circuit), so I can't stress enough that you have to be SURE that you've got the right one before you start cutting and connecting. If connecting the unit to a Kenton Electronics' "PRO-2"(MIDI to CV/GATE/S-TRIGGER Converter), be sure to set the appropriate "AUX" trimmer on the front to absolute minimum! This probably goes for other units too. If you only get to do a short modulation although the duration should be longer you probably have too much voltage going into the SH-101, thus causing it to overload. Turn down the voltage and it will probably work fine. Hallvard Tangeraas, Oslo, Norway (hallvart@ifi.uio.no)