DaveKennett

Dave’s Conn 642 MIDIfication PART 2 While awaiting delivery of parts, I decided to firm up my plan of attack. I already had an Asus barebones computer into which I had installed a 3 Ghz P4 processor, overclocked to 3.3 Ghz. I had been using it as a home theater computer, but the addition of a DVR pretty well put it out of business. It was suggested that a fast single core processor might be better than a slower multi-core anyway. That certainly was the case, as this computer worked flawlessly using the Miditzer fluidsynth and the onboard AC97 audio. I thought I might use the organ amplifier and speakers for the Miditzer, but a temporary hookup proved very unsatisfactory. I had an old stereo system, consisting of a Heathkit AR1500 receiver, and the Heath version of the Acoustic Research AR3 speaker systems. A quick trial was beyond success. The Miditzer sounded beautiful! My jubilance was short-lived however. Upon hearing some strange sounds, I removed the grill cloth and found that the foam rings surrounding the woofer speaker cones was disintegrating. I remembered an outfit in nearby Cleveland, Ohio that did speaker repairs. Empirical Sound did a top-notch repair job for $30 a speaker. Happiness returned! I have a maintenance manual for the Conn 642, so that made things a little easier. It was made in the mid to late sixties and is fully transistorized, but a little too early for integrated circuits. The top lifts up and the keyboards flip up, exposing a wonderland of electronic construction. It’s easy to understand why such an organ cost so much. I would try to keep everything intact. There are ten contacts under each key in the solo manual (fewer in the accompaniment), one for each of the keyed tibia voices, with the remaining contacts being used to mix various audio waveforms for all the other voices. There is a +30V buss that is switched by the keyboard to turn on various tibia notes through a keying transistor - one transistor for each note. The +30V is fed to a rotatable rod that runs the length of the keyboard, and there is a rod for each of the tibia tabs. Only one side of the rod is conductive, and each tibia tab (16', 8', etc.) rotates the rod through a control cable like those used to operate bicycle hand brakes. When a tab is down, the conductive side of the rod can make contact with one of the contacts under any key which is pressed. Thus, when a key is pressed AND a particular tab is activated, the appropriate note will sound What an awesome system! It is that keying voltage that I will use to feed the DIN shift registers. +30V would quickly wipe out the shift registers, so I added a 62Kohm resistor in series with each input to form a voltage divider with the 10Kohm pullDOWN resistor (my modification as mentioned in part 1) on the DIN board. This gave me a little over 4 volts at the chip. The chip specs state anything over 5 volts will destroy the chip, and that anything over 3 volts will be seen as a high. The 4 volts was an attempt to strike a happy medium. I had to add an isolation diode at each keyer as well so that the tibia sustain would work. If you are considering a similar modification to a Conn organ, I can provide additional details. Two DIN modules were used for each 61 key keyboard, so one CORE module and four modified DIN modules were used for the two keyboards. The pedalboard did not lend itself to any such technique, so a standard DIN module was used for the pedals, and another for the combination pistons I decided to add. These two modules were used with the second CORE module, which also accommodated a single potentiometer for the expression pedal. More about this later. I also ordered a 15" Hyvision touchscreen monitor from Newegg for the stop tabs. The board kits arrived, so it was time to heat up the soldering iron, and get busy. There are excellent step-by-step instructions by Jim Henry at http://virtualorgan.com/virtualorgan/FileLib/Assembling_a_MIDIbox_Core.pdf, and there is additional information at avishowtech.com and uCApps.de. If you haven’t soldered before, take the time to learn, as well as recognize a poor or cold solder joint. A poorly constructed module will surely insure failure. Look around the uCApps.de forum, and you’ll find plenty of help. You’ll need a 15 or 25 watt soldering iron, and I highly recommend a soldering stand with a sponge for cleaning the iron. Both are inexpensive at Radio Shack. You’ll also need some rosin core solder, wire cutters, and needle nose plyers. The ICs are the only components that are really sensitive to electrostatic discharge, so leave them in their protective wrapping until the bitter end. Since you probably don’t have anti-static workstation, you must be extra careful when installing the ICs. Get into position, sit perfectly still, and touch a grounded object - something metallic that is likely to be grounded through a grounding electrical plug (computer case?). While you’re handling the IC, do not move your feet or squirm in your chair. So far, this has worked for me. As mentioned various places, the use of a display is optional, but I sure got a nice warm fuzzy feeling when it lit up and started telling me things were OK. Jim Henry includes a link to general information on displays in his CORE assembly article and also wrote a nice tutorial on wiring a display at http://www.midibox.org/users/jim_henry/building_a_midibox_lcd_cable.pdf. A data sheet came with the display I ordered, and the connections did indeed match Jim’s. Be sure to orient the connector properly when plugging it into the CORE board. I built only one of the two CORE modules, and tested it before proceeding. I next built only one of the DIN boards as an initial test. That way, if I were doing something wrong, I would discover it before building any additional modules. To test the DIN board, I’ll have to load some software (firmware?). While I have been fiddling with computers for some years now, this process was still the most challenging. We’ll talk about that in part 3. Dave

Dave’s Miditzer 216 PART 1 When I first downloaded the 216, I was so taken that I knew I had to have a console for it. We had a 1960s vintage Conn 642 two manual with 25 pedals, but I was somewhat tired of the sound. Could that be the midi source for the Miditzer? Could I keep the Conn operable and still do the midi interface? After a couple weeks surfing the net, I decided to proceed. It then took about two months to complete after ordering the first supplies. But there were some bumps in the road. Special thanks to all those on the forums for smoothing out the bumps. I hope that by telling my story, I can make the path easier for others. Some internet research led to several hardware options that seemed feasible. I decided to order two CORE modules and six digital input (DIN) modules, along with some rainbow ribbon cable and connectors from SmashTV (http://www.avishowtech.com). They were shipped on July 25th. SmashTV was quick and accurate, but here’s what I did wrong. 2 CORE module kits w/PIC18F452, one Sysex ID 00, and one Sysex ID 01 No problem here! 6 DIN module kits I was planning to use the keying voltage from the Conn to apply a + voltage to the DIN board when a key was pressed. The board is wired with pullUP resistors, so that a key grounds the input when pressed. I had to modify the board for pullDOWN resistors. The schematic for this board at http://www.ucapps.de showed that a jumper could configure it either way, but that is not the case with the SmashTV boards. On the plus side, they use Dual In Line headers which mate nicely with easy to use crimp type IDC connectors. If anyone is interested. I could post the details for the modifications separately. 3 1/4" Potentiometers Used one for single expression pedal, broke one, and have a spare. 4 PCB mount MIDI jack Didn’t need them; they are included in the CORE kits. 4 2 pin SIL connector Used two for power hookup between COREs. 3 5 pin SIL connector Did not use. 2 IDC connector 16 pin Used one for connection of CORE to display (for troubleshooting) 1 (meter)16 conductor ribbon cable Used about a foot for display (soldered to display) 35 IDC connectors 10 pin Trashed a couple - ran out - had to order more. Order at least six more than needed. 6 (meter)10 conductor ribbon cable WAAAY less than needed. I ended up using about 80 FEET. I also ordered a 00DM2004A-B-B6NTW 4-line display from 411 Technology Systems in San Marcos, CA.(Used only for initial programming and troubleshooting) It served its purpose, and now sits in the box of leftovers from my project. That should be about enough for now. Next, I’ll talk about construction and programming the CORE modules. Dave

Thanks to all! I get my answers - and I plod along to the next step. I have discovered some things that might be useful to others, and soon should have a complete report on the project (midifying Conn 642). All the midibox stuff is built and tested, and two keyboards are working. I am now making the combination button panels to go under the keyboards. After that, it's pedals and expression - then maybe learn to play a little better! What a wonderful thing is happening here! Dave

Thanks Per, When I woke up this morning, It occurred to me that, unlike notes, the piston settings would be specific to Miditzer. The pistons and stops settings in setup now made sense to me. Your specific code examples clear up things even better. Thanks, Dave

Hi PK, Four DINs on one core for the two manuals, and two more DINs on another core for pedals and pistons. All the hardware is built and tested, but I now need to configure the second core. Then it's into the organ! Dave

Back again! Thank to all for the help on the codes for notes and keyboards. I now have two 61 key manuals working w/midio128 on one core. I guess I'm still missing something, as I have no idea how to program pistons in the .ini file. It looks like I just program the pedal notes with a 92 code for channal 3, but I could sure use some help with the pistons. Using another core with two DINs with midio128, I plan on adding 25 pedals, and 10 buttons under each manual. It looks like I can use a modified midio 128 to add an expression pedal, or a hex file from Per S to add 3 pots. I'm still a little confused there. I soon hope to start wiring in the Conn 642. Thanks for all the help Dave

I have built one core and one DIN. They work! But more questions arise. I'm digging into the .ini file and can see how many things are set, but for each answer, two or three more questions appear. I'm using one core with four DINs for two 61 key manuals, so I would have one manual (wires 1 - 64) assigned to channel 1, and the other manual (wires 65 - 128) assigned to the same notes on channel two. It could be other channels, but that's the Miditzer default. There was an earlier discussion about this, but the OP said "never mind, I've found it". I searched again through the sample midio128 file, but to no avail. I'm also somewhat confused about the examples being more complex than the list of note assignments. Actually, I'm confused about a lot of things - but I'll get through it! Once I get that, I'll try creating a SysEx file. That looks like real fun! Thanks to all for all the help! Dave Seems like this forum is responding reeeaaally slow on my computer today.

Thanks to all! Orders have been placed, and I am waiting anxiously. As I said earlier, I plan to invert the logic from the organ keys, and change the 10k resistors to pull-DOWN. I then can tap a 30v keying voltage from the organ through about a 56k resistor (giving just a little less than 5v). My question is this. What would be the down-side to increasing the resistor value from 10k to say 27k. I could then use a nominal 150k to drop the voltage. The 30v keying buss has fairly poor regulation under varying load, due to a 400 ohm resistor feeding the buss (probably for power supply protection). I thought this could help when several keys are pressed. Otherwise, I could probably reduce the value of the 400 ohm resistor. The inputs to the internal organ keyers are in the order of megohms. Any thoughts? Thanks, Dave

Thanks to all for the informative responses. New shopping list for SmashTV Two CORE modules Six DIN modules Assorted connectors and cables. I see that I must order both modules with different device ID, but it looks like as long as I specify a character display, a variety of types will work. I have seen one specific type recommended, but it was out of stock. Digi-Key and Mousser have such an overwhelming variety, that my confidence is shattered. I would appreciate any specific recommendations. Thank again, Dave

Wow, thanks for the quick replies, and for the welcome nILS. OK, here’s my new list for SmashTV. One CORE module, Four DIN modules, One AIN module, Assorted connectors and cables. While I could run the expression pedal directly to the CORE, I would still need 25 DINs for the pedals. By doing it this way, I could still connect the pedals, with inputs still available for the future. I would be running both midio128 and midibox64. Anyone see any problems with this approach? Oh! I guess I still need to work out details for a display for setup. Thanks again for all the help. Dave

Hello all! I’ve been lurking around for awhile, and I have learned much. Thanks to all of you who so generously share your time and talents. I THINK I know what I need. But I still have some questions, so here goes. I have been playing with Miditzer 216, and have decided to try to interface it to an old Conn 642 theater organ (two 61 key keyboards, 25 pedals, one expression pedal) with midibox. I would like to leave the organ intact. There is a 30v supply in the organ that is switched to transistor keyers through the keys. My plan is to use that voltage through a 56k resistor from each key, which would form a voltage divider with the 10k resistors on the DIN board, putting about 4.6 volts on the inputs. It appears that those 10k resistors can be configured as pull-DOWN resistors, with the input logic reversed on the DIN board. Is this true? Assuming the above works for the two manuals, the pedals are another story. My plan is to use reed switches and magnets on each pedal, thus completely isolating midibox. I think I can add a 10k pot to the expression pedal for isolation as well. Does anyone have a good source for the reed switches and magnets? It looks like a CORE module and 4 DIN boards will handle the keyboards. Can an AIN board be configured to handle the expression pedal, as well as the 25 pedals as digital inputs. This would leave some inputs from the AIN module, as well as the DIN modules to someday be configured as pistons (presets under the keyboards?). I plan to order kits from SmashTV. Can all this be connected to one CORE? (With PIC18F452?) If I need two COREs, should I get different addresses for the PIC ID header? If I use two COREs, can I merge the MIDI in one of the modules? It seems I should have an LCD display for setup. Is two row alphanumeric sufficient? Can a cable connect directly to the display? At this point, I’m simply trying to order the right stuff, and any suggestions would be greatly appreciated. I’m sure more questions will arise. Thanks again to all those who contribute so much to this forum! Dave