Schlagwort-Archive: knob


after 4 weeks of drying the boards on my heating, i tryed to arrange a date with doogie, who helped on the phase one. not knowing, how the pitch-wheel and the floppy was connected, the synth was just closer to be doomed. but, after 6 weeks or 7 we arranged a double day, to slowly rebuild the kurzweil from its parts.

first test run
kurzweil loose connected

reassembling … how to start without a manual on that level. so … isolating the parts from the case and other connected parts, was in the focus here. the power supply was also not to trust, but with a headphone, we went sure, that no noise nor sine waves came from that part, beside the expected voltage.  it looked good for the moment, power was there, no cable was missing, the defect buttons were easy to change … so lets try it.

second test run
kurzweil loose connected

nope, nothing to see on the display, not lights on, no sound nor growling from a short cut were to hear, so we ripped all parts of the case and connected each cable to a part, that was numbered or signed in somehow. but … fail. some 2-3-4 ends of cables were without a mark. hm, …. we tried to start the engine, but one of the ribbon cables starts smoking, a sure sign of a short cut, that was not the right port for that cable.  we stoped and looked on each board, not seeing the difference, we have had to made. so we started again, and the cable went hot instantly – again.

kurzweil inside
upside down inside the kurzweil

the engineers on kurzweil showed us, where the fork is hanging around. pumping current over a tiny, 0.14 mm² of cable, couldnt be more worse. they used big cables for big wattages, but why did they did that different, on the engine board then? we looked closer after some minutes, or was it hours of cluesless talkings. we suprisingly found 2 connectors without a cable, so we switched something between the sampler, i think the scanner and the engineaudio analog or digitized, anyhow, could be the case. we stoped breathing when we switched on the power plug again … and … the display starts working. but, as i estimated on old-fashioned-hardware, each part of the system needs to be connected the way it should, so we couldnt check part by part, we had to stuff all together, with the hope, its allright then.

k2500 boards
k2500 display and scanner board

the five knobs or buttons on the input board, which were dead as distances holder, they were quickly replaced by some from the a-z/+-# keyboard. five pieces, let one cost 50 cent, made that accident happen, that we started to enjoy then later. the system came up, the boot-cycle went successfully done and the thing came to life. but having everything upside down, not knowing what buttons to push, we tried some intuitive haptics by accident, but after everyone of us three tried it, some preset with playable pattern suprised us thru the headphones and speakers with sound. the rest was routine to not mixup the three packs of screws and as we nearly closed the parts of the case, the kdfx board went back to my mind.

i had spare parts to drop in, with more power, more harmonic distortions and bigger rooms to simulate. but first, i wanted to get warm a bit with that tier, to check, if its worth the switch from software-based production to this kind of hardware. i would notice, it is it worth, but fiddling the menue was not funny, so the vast.programmer needs to be setup … next or the very next weekend … some day. that reopening, droping in, updating the firmware with a floppy drive, then stimulating to live once again will need a long way to get warm with that idea. one nice part is, that after that years, the software is still online on kurzweils server, that is a big plus in that whole story.


a friend organized a used kurzweil k2500s, without function, but with a kdfx-card for 50 bugs. even the spare parts would bring some dozen or hundrets on eGay, if the resurrection wont happen. s on the item was the sampler, it was included with some megabytes of ram, to capture sounds from outside the synth. it was a synth workstation with scsi, floppy  disc and some pre-burned rom to create sounds from 48 voices, with several dsp-chips. but actually, not more then noise came out of the headphones and mix-out, this time.

kurzweil from rear
kurzweil on the knees

that machine had a price tag of around 8000 $, when it was available in the stores, but fully equiped it could costs something like 19.995 USD.  after 18 years, since 1996, when it was build ( born ) the inflation and process of development smashed the price, but wait. on the web some people were able to pay something like 600 or 800 bugs, some with hard-disc even for 1500$ or was it €? but first, it needs to be opened and repaired. i heard, that the owner before tried to fix the death buttons with to much „flutschi“ – the expats name for contact spray. that evil stuff killed not even the buttons, the fluid went over the whole pcb and made irregular connections between the input knobs and switches. grant!

kurzweil cables crowded
crowded cables in the kurzweil

so we opened the case carefully, without knowing, where what was placed. some ribbon cables with different sizes, some black audio or what else matter wants to flow thru that line? we would find out later, that the star-scheme of the power distribution was grown by need, so it looked pretty unsorted and far away from engineering forces. but what, where was it from … california … so its all big block here or what? removing cables, writting some hints on the ports or the cable itself should help to re-build that thing, some days later – was the plan. also checking and repairing some of the buttons needs to be done then later on.

kurzweil cabling
inner cabling from the kurzweil

but digging deeper inside the top-half of the case, extracted more and more confused coupled cables between everything. and the best, the input terminal was so retared placed, that the whole thing was needed to dis-assebled, to get in touch with the human-interface. no one during the construction thought about buttons for cents, which gonna die after some thousend or millions of clicks. so, maintanance, patience … hopefully having enuff bread-crumbs droped on the way to the front pcb, and markers, … around. the parts inside had all in all a very cheap optic, the transistors on the output-board, were such 6 cent types, you wouldnt take for your weekly macgyver-course. the ribbon cable and the connectors where fixed with metal-safeties, but that non-flexible line is worse when you want to build something extraordinary.

kurzweil job wheel
k2500s job wheel

but wait, how to clean up that mess – was the first question, when i heard about that beast. unprepared, but motivated, we digged out the pcb after some hours and due the lack of material, we decided to shower everything with hot water and some minutes of dive, we hopefully cleaned the flutschi away of the board.  kurzweil droped a lot of energy inside the psycho-acustic-algorithms, that the discussions from the hife-scene from that time, was less then a farce. the dsp and the software running on them was the fat steak of the machine, the keyboard wasnt even layed on on roses, instead, simple mdf-wood was takes as spacer.

showered input panel
kurzweil in the shower

so, without some fuel of isoprophyl-alcohol, the cleanup would be a mess, but it wasnt that harsh. it took some 15 or 20 minutes, to shower both input boards twice and then the swom in that bath for half an hour or so. drying the boards, wouldnt be a thing, but the cables were somehow sensible to that fluid. so the boards went drying on the heating for 2 weeks or more, then i would be motivated again, to put everything together with the  want and need of harmonic synthesis from that famous piece of hardware.

so, we need to be patient and come back in some days, to take part 2 of that ride.