bentron

ok, the box works again. i fried the pic :-[ seems like i shortet the gate pin somehow while testing the gate driver ic. however, the friendly guys in the chatroom ;D told me to use the udn2981 8 Channel Source Driver IChttp://www.pescadoo.net/annexe/simda/chips_data_sheets/UDN2981.pdf to increase my gate voltage. i got one of them yesterday and it works perfect. :D no additional circuitry required, just connected it like described in the datasheet. thanks alot to all of you for the fast support! greets, bentron

Ok, i'll try to describe the problem as precise as possible: I'm using an AOUT and the dac's are still working. means i have correct cv voltages on all eight channels. Also all gate channels are working except channel 4 wich is the one i connected the ULN to. It doesn't react to any midi messages and outputs a constantly varying voltage between about 1,5 and 2,5 volts (i measured directly on the corresponding pin at j5, to sort out possible shorts at the jack sockets and wires). I connected the ULN exactly as described, i just used some wire for testing purposes and connected pin 9 and 10 to ground and +12v and then wired the gate out to pin 1 measuring the voltage at pin 18. When i didn't mesure anything, i double checked the connections to the ic, but everything ok. i measured every pin of the ULN while connected, when i noticed the gate output was dead. Interesting thing is: the (broken) gate delivers, as described above, a constant gate voltage about 2v. when i reconnect the ULN to the broken gate, the voltage drops to 0v. ??? ??? So all in all it's "just" gate channel 4 thats affected, everything else works properly. greets, bentron

hi seppoman, thanks for your response. i picked up a ULN2803 today and just connected it like described in the datasheet - means i didn't use any additional components, just the ic. That didn't work and now i have a big problem: the gate port i connected to the ic is dead - it produces a constant voltage between 1,7 and 2,5 volts and doesnt react to midi messages anymore - did i destroy the pic? ??? ??? i'm sure i had the right pinning on the ic but should i have used any additional components? and is there any possibility to get the gate port back working? i thought of replacing the software in the pic - i´ll try that and post the results. any additional suggestions wuold be great. thanks & greets, bentron

Hi there, i´ve just completed my midibox cv and it works really good. But i have one (maybe stupid) question regarding the gate voltage: I need to have a higher gate voltage than 5V, because i have a Roland SH-1 Synth wich doesnt react to the gate signal from the box, so i read the manual and noticed that it starts triggering at about 7,5 V. So is it possible to increase the gate voltage? i mean, i did a previous project where you could just increase the circuit supply voltage to increase the gate voltage. but i have doubts that this will also work in this case. And since i am pretty new to electronics, i will not try it either :) I´m using the AOUT Version, so maybe there is an option to increase the voltage only for the 2 gates provided by the AOUT? Thanks in advance for your suggestions! greets, bentron

hi, well i´ve tested several configurations with all 4 AOUT_LC boards, but always the same effect. even if i swap the lc modules around. :( So i think the problem resides on the core. The only thing that comes to my mind now is the crystal on the CORE. i´m not sure if it's parallel cut, since the datasheet doesnt give any useable info. I don`t have another crystal to test, so before i start rippin the old one out and gettin a replacement: Is it even possible that this causes my problem? thanks for the info on the s/h, but i think that's getting too complicated in the end,. ;) since the zipper noise isn`t really a problem anyways, my ears are just very picky ;) Intentionally i wanted to build the midibox cv with the AOUT module but i had big trouble getting the MAX6007B shunt. Any supplyers in EU or substitute parts known? Thanks & best regards, Max

hi, after some failed calibration attempts i decided to completely finish the unit and put it in its housing to eliminate possible error sources. Well that was quite a success since the button noise, constant gate voltage and the strange rebooting are gone now, ye-haw ;D (must have fed some voltage to the ground with those alligator clips ;) or something like that) But one problem remains: I've set the all cv channels to 8/8 bit, see a part of the code here (but i assume it`s correct): but still i get some strange behavior on every second cv channel (e.g. 2,4,6,8): While calibrating, the 1V setting cannot be reached - maximum possible is about 0,6 to 0,8 Volts - while the other voltages are ok (min, max, 2,4,8,) When connecting a synth then, the octaves are like - it's hard to describe - cut in half. the 4 lowest notes of every octave are played twice, so when playing the complete octave, the notes are like this: c1, c1#, d1, d1#, c1, c1#, d1, d1# an then it continues with the same notes one octave higher. I've tried with 8/8 V/OCT, Hz/V and 12/4 Hz/V with several analog synths but it`s always about the same, so the problem must source somewhere else. And again, CV Channels 1, 3, 5 and 7 work perfect, without any trouble. Any suggestions? Thanks again & best regards, Max p.s.: any recommendations on a simple s&h ciruit to eliminate that zipper noise? i assume a part of the SHX8 would do, but as mentioned, my electronic knowledge is very limited ::) :-\

I forgot to mention, that i noticed a problem while calibrating: on the second channel of every AOUT_LC board (CV2,4,6,8) i only got about 0,6-07V with the 1V setting - while all other voltages where ok. HMM, while checking it right now, i notice that the 7805 on the core gets very hot - even though i swapped it with a new one and now using a 9VDC 200mA instead of 9VAC 800mA. i don`t have any clue ???

Hello everybody, i´m new in the Forum and let me first say thanx to Thorsten for this great diy project!! I've just successfully completed a Midibox CV with 4 AOUT_LC Boards, everything seems to work in terms of hardware and software - means i´ve tested all voltages, burned bootloader, uploaded mios & MidiboxCV App. All soldering points seem to be fine. But when testing with my SH-101 and MS-20 i noticed some strange behavior: When plugging the gate into the sh-101 i triggers the synth constanly with a weak gate signal. The 4 buttons connected through DINX_1 make a very audible noise when pressed - on higher octaves it seems almost like the buttons are triggering/gating the synth. ??? And while plugging the gate or cv cable to the Patch-Panel of the ms-20 (e.g. shorting the pins), the midibox cv reboots instantly. Besides that, the triggers and cv's themselves all seem to work - but all with the problems named before. I'm pretty sure i've set the correct output-curves, jumper settings, etc. I´m pretty stuck with this problem, since my electronic knowledge ends when it comes to trace problems in a circuit :-[ Any suggestions on this? Thank you in advance and best greets from vienna, Max