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 Forum index » DIY Hardware and Software » Thomas Henry designs
My twin SN-Voice
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State Machine
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PostPosted: Sat Apr 07, 2007 6:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
And don't be affraid for it being too hot, better a bit too hot than too cold as when too cold soldering takes a long time


Yes, I agree with that advice Jan but just be careful in some instances that you don't lift or damage pads when setting the iron at higher temps for the tough ones. Wink A 50 W regulated iron sounds good for the task set to about 750F.

Bill
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State Machine
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PostPosted: Sat Apr 07, 2007 7:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
shouldn't the env/lock switch just directly effect the env on the noise section without patching?


The envelope/lock switch is wired for only two states but the chip will support 4 modes. The SN voice supports MIXER (LOCK) and ONE SHOT modes (GATED). When in the envelop LOCK position, which is MIXER ONLY in the sound generator, the GATE is ineffective and the chip will produce either noise or pulse continuously depending on the state if the PULSE/NOISE switch setting. When in the ENV mode, the the mixer will only output a signal for the duration of the chips internal one-shot pulse. This one shot is triggered by the GATE input. You can, however, sweep the noise within the duration of the GATE pulse for some cool sweeping gated sounds!

Quote:

oh and the noise bleeds into the tri out a bit is that normal?


Hmm, I have not used the TRI out that much but did not take notice, I will have to check and see about that. I would assume the S/N ratio should be OK but not fantastic. Noise is, well, noisy, especially with slammin' rail to rail digital type noise running around these circuits. Is it only bleeding when the NOISE is selected, or, does it always bleed through? I have to assume for a moment that the VCO will keep running, which is what the triangle output is derived from, even when noise is selected.

Quote:
the PWM still doesn't work though. could that normalled connection between the J7/lfo out and J3/linput be part of this? also it does now drop in pitch a tiny bit when its on either lfo or 50% ( i'm not sure if i have the switch positions wired right so it could be either one until i hear it working right)


The normalization of J3 and J7 is so that the LFO output can frequency modulate the VCO. The the LFO can also modulate the pulse width via the PWM selector S5. You can modulate frequency and pulse width together. If you want to only modulate the pulse width, then turn the LINER FM potentiometer R46 so that no shift in frequency is heard as the LFO changes or stick a plug with no signal into the J3 to break the connection from the LFO output on J7.

I would recheck the pot and switch wiring since this will most likely be the cause of your PWM troubles.

If you request, I can supply a sound file that sonically describes the proper operation of the PWM operation.


Let us know how you do ......
Bill
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Scott Stites
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PostPosted: Sat Apr 07, 2007 8:01 am    Post subject: Reply with quote  Mark this post and the followings unread

On the breadboad, I don't recall experiencing noise bleed-through with the LFO output.

Is your LFO working yet? Sometime during the development of the SN-Voice, I did manage to toast one of my fat boy's LFO's - that was when I was switching a lot of wires and signals around and think I inadvertently connected the wrong wire to the wrong terminal. I made a few blunders like that when messing with the SN-Voice on breadboard, but that's the only one that seemed to have actually affected (damaged) the SN76477.

Cheers,
Scott
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para



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PostPosted: Sat Apr 07, 2007 10:30 am    Post subject: Reply with quote  Mark this post and the followings unread

no the bleed is through the out of the tri vco, not the lfo. the lfo has always worked just fine by itself, i like it a lot actually. and the bleed isn't horrible at higher frequencies but it is pretty bad at the lower bass end. it does only happen with the noise out selected and does react to the all the noise controls. it is full on bleed

is this correct?

------------


for pulse/square audio out - when selecting the "env" selection switch it does nothing at all. it kills it completely. and the envelope will not effect it unless it is patched to do so. the "lock" will let it play constantly, though it does not let the envelop effect it at all.

this is correct i assume?

when the noise audio out is selected instead of square - the "lock" position will play constantly and will allow me to use the key input. when in the "env" position the key input will not work at all. only the gate will work.

is this correct?

-----------------------------------

i thought the key in and gate in were just for the envelope but the key is actually just for the noise along?


-------------------------------------

the PWM switching is the main trouble now. but please ignore the part where i tried to explain in passing that they are new switches that i have never used and i'm not sure if the pin and knob position will match up or will be reversed. it doesn’t have anything to do with my trouble i assure you, tested and working as you would predict them to, also please don’t waste your time making samples. your giving me enough of you time as it is.


anyway you said you think it might be something to do with my wiring but i have already said that i have traced each PWM feed, the lfo and the env back to their points on the board j2-10 and j3-6, and i get nothing at all. its not the switch or the wiring they have been tested again and are working as they should. the signals are just not getting to the J sections of the board. j2-10 and j3-6 give me nothing at all? the little bit of pitch change i mentioned before was the 5vdc out which is working correctly so that can be ignored as well.


i need to figure out what’s happening with j2-10 and j3-6? how do i do that? the schemes you sent just go to name tags and don't show the trace path. for example are they buffered with a 444 just before those points maybe, and i fried it? if the 4046 went something else might have too.




steven
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State Machine
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PostPosted: Sat Apr 07, 2007 11:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
for pulse/square audio out - when selecting the "env" selection switch it does nothing at all. it kills it completely. and the envelope will not effect it unless it is patched to do so. the "lock" will let it play constantly, though it does not let the envelop effect it at all.

this is correct i assume?


Yes, you have the total concept of the envelope select logic now Very Happy

I will have to address the two other questions a bit later this evening as I have to take a run out for a bit .... I am starting to grow mushrooms under my arms from being in a dark studio all weekend Shocked

Bill
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para



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PostPosted: Sat Apr 07, 2007 11:16 am    Post subject: Reply with quote  Mark this post and the followings unread

i unfortunately did my panel placement a little wrong then. i'll have to fix that with the other two.

enjoy the weekend
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State Machine
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PostPosted: Sun Apr 08, 2007 11:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
i need to figure out what’s happening with j2-10 and j3-6? how do i do that? the schemes you sent just go to name tags and don't show the trace path. for example are they buffered with a 444 just before those points maybe, and i fried it? if the 4046 went something else might have too.


Hmmm, why do I get the feeling that you are missing this attached document. This panel wiring diagram and the schematics you have should answer all your questions as to how things are wired into the board. This certainly should answer what J2-10 and J3-6 do.

Let me know if this helps Very Happy

Bill

[editor's note: added a PDF version. Not everyone can read .doc files. --mosc]


pot_wiring.doc
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pot_wiring_277.pdf
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para



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PostPosted: Mon Apr 09, 2007 2:59 am    Post subject: Reply with quote  Mark this post and the followings unread

no i have that.

i have measured those points on the board and they are dead. they should be feeding me the envelope signal and lfo signal right? but i get 0.000 - the env and lfo work just fine out of their patch points though.




steven
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State Machine
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PostPosted: Mon Apr 09, 2007 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
have measured those points on the board and they are dead. they should be feeding me the envelope signal and lfo signal right? but i get 0.000 - the env and lfo work just fine out of their patch points though.


I might expect these points to read very low as there are, I am not in front of the schematic, high value multi meg-ohm resistors in series with these signals. They are not buffered by any amplifier. These resistors tap off the attack/decay capacitor and the VCO capacitor then are sent to the PWM switch for routing into the sound generator.

When I get home I can give you some resistance measurements that you can perform that will tell us if things are OK.

Bill
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para



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PostPosted: Mon Apr 09, 2007 1:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

maybe my guess is wrong about that being the trouble then. i was expecting them to be mirrors of the lfo and env outputs or close to it. i would appreciate you taking the time to check that


steven
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State Machine
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PostPosted: Tue Apr 10, 2007 9:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
maybe my guess is wrong about that being the trouble then. i was expecting them to be mirrors of the lfo and env outputs or close to it. i would appreciate you taking the time to check that


Sorry, I did not get to that last night. I will do something this evening and offer you a few more suggestions. Since you have a DVM handy, I will offer troubleshooting suggestions that involve only that.

Bill
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State Machine
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PostPosted: Tue Apr 10, 2007 6:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
have measured those points on the board and they are dead. they should be feeding me the envelope signal and lfo signal right? but i get 0.000 - the env and lfo work just fine out of their patch points though.


OK, I took a few resistance measurements for you. Try these resistance measurements. This are assuming that the envelope and LFO circuits are working correctly as you stated they were.

1) With the SN Voice deenergized, place the PWM rotary switch to the LFO position.

2) Measure the resistance from IC4-3 to IC1-19. You should get between 4 and 4.5 meg ohms. IC4-3 is the LFO buffer input. IC1-19 is the PITCH input to the sound generator IC.

3) Place the PWM rotary switch to the ENV position, measure the same points and you should get between 6 and 6.5 meg ohms.

4) Measure IC1-19 to ground. You should get 1 meg ohm.

R63 is mainly responsible for the 6 meg resistance.
R62 is mainly responsible for the 4 meg and R53 for the 1 meg.

These resistors are all involved in the PWM biasing into the PITCH pin of the CSG chip, pin 19.

The PITCH input is really a miss leading name as this is really the VCO duty cycle control. The duty cycle is the ratio of the voltage at pin IC1 pins 19 and 16 times 50 ((Vpin19/Vpin16)x50)%. This will be the percentage duty cycle.

It is also important then to check that R18, MOD CTR TRIM is set correctly. Check that R18, R27 are correctly installed. These components set the voltage at IC1-16, EXT VCO control. This voltage should be no more than 2.5 V.

This should be enough information to get the PWM control working correctly.

Bill
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para



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PostPosted: Thu Apr 12, 2007 12:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks for that bill. i've been laid out sicker then i've been in years for last couple days, so things are still in slow motion. i'll try and get this over with tonight.

much appreciated !!
steven
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State Machine
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PostPosted: Thu Apr 12, 2007 3:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
thanks for that bill. i've been laid out sicker then i've been in years for last couple days, so things are still in slow motion. i'll try and get this over with tonight.


Oh sure, get well OK. Sorry your so sick. Crying or Very sad I had a very bad flu about 2 months ago that really put me down for a week so I know the felling my friend!

Bill
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para



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PostPosted: Wed Apr 25, 2007 12:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Bill, i'm sorry to drag this back up again and i'm sorry to have taken so long. i stayed sick and useless for a while and then got really sidetracked with other stuff.

so it seems to be a combination of things guided foremost by my stupidity. first i hadn't calibrated it at all, not having a usable scope, and thinking that i should get the PWM and noise working first. then when doing your testing i tried to calibrate it as much as i could and turned R18 then i noticed that i had the PWM strength knob i added wired backwards, so i should have at least heard a very faint pulse when turn down all the way, but in my defense R18 was turned down so no LFO was coming through anyway. now although the LFO is feeding the PWM when selected its incredibly weak. it can only be heard if the VCO pitch is in the mid octaves. and the ENV does nothing at all still. i answered your questions below, but i want you to understand that i don't really care anymore. sure its lame that these features don't work with the PWM switch but i can just patch them in which is completely fine with me. if at some point something clicks in your head based on the measurements below then i'd love to try further but i think i've wasted enough of your time. which i am very appreciative of by the way. i'm ready to move on though, i have so many other things to be working on its crazy. i have a box of pcb’s that need some serious attention, two more SN's too.




2) Measure the resistance from IC4-3 to IC1-19. You should get between 4 and 4.5 meg ohms. IC4-3 is the LFO buffer input. IC1-19 is the PITCH input to the sound generator IC.

i get an incredibly slow rise to 4.95 M


3) Place the PWM rotary switch to the ENV position, measure the same points and you should get between 6 and 6.5 meg ohms.

i get an incredibly slow rise to 21.5M
and 50% position is giving me the same 21.5M


4) Measure IC1-19 to ground. You should get 1 meg ohm.

i get 63.9k


It is also important then to check that R18, MOD CTR TRIM is set correctly. Check that R18, R27 are correctly installed. These components set the voltage at IC1-16, EXT VCO control. This voltage should be no more than 2.5 V.

IC1-16 to ground - i get 0.48v


oh and i have tested all of the resistors you mentioned to make sure i didn't get them wrong, but they are all correct.


don’t know what to say except thanks again,

steven




-----------------------------------------------------------------------------



here’s a really bad photo of my SN panel. the panel is 1/4" plexi and its actually florescent red / hot pink (i can’t figure out the pink thing either, i think i was brainwashed?) but the lacquer and the sticker are making it look orange on camera, it looks a lot better in person. notice the placement of the noise ENV gate and key, as i said before i messed up and have them in the wrong section but its really not a big deal. oh and i haven't grabbed any knobs for the rotary switches yet. 3 TH-XRVCO’S next to that. if i ever meet Mr. Henry i think i should probably buy him a drink or something.





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synthmonger



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PostPosted: Wed Apr 25, 2007 4:34 am    Post subject: Reply with quote  Mark this post and the followings unread

That looks great Para! Ain't nothin' wrong with using pink either!

What did you use to adhear the labeling?
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State Machine
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PostPosted: Wed Apr 25, 2007 1:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
4) Measure IC1-19 to ground. You should get 1 meg ohm.

i get 63.9k


You should be getting about a meg-ohm there. This reading you get will severely attenuate your signal level getting to this pin and will get barely any PWM. Either this resistor is wrong OR something is shorted across it. Take a close look at this portion ....

I will take a longer look at your other observations ...

PS: Cool, colerful panel !!! Cool

Bill
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para



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PostPosted: Wed Apr 25, 2007 7:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks, for those without a laser printer there is papilio :

http://papilio.com/inkjet%20glossy%20clear%20transparent%20vinyl%20adhesive%20media.html

i also use the white stuff when i can because the white backing shows off the print better. the clear isn't a very dark black and some colors come out faded, so you need to hit it with a clear coat of some kind to get it to bleed a little and darken the print.

all the stuff i do is made with papilio: http://thesquarewaveparade.com/


---------------

Bill that doesn't sound good. i guess i should go through and triple check my resistors. the thing is i am far from having the color code memorized so i have to constantly reference back and forth and then add them up. takes forever, but i guess its good practice.


when i was populating these boards i was scrapping the barrel on my supplies so i used every last one i had in some cases and then had to wait for another shipment. so they came from a few different places and could have gotten mixed up. its more likely that i have the wrong value in then anything else. you think i should just focus on the section that you mentioned before?


steven
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fonik



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PostPosted: Wed Apr 25, 2007 10:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

para wrote:
the thing is i am far from having the color code memorized so i have to constantly reference back and forth and then add them up. takes forever, but i guess its good practice.
when i was populating these boards i was scrapping the barrel on my supplies so i used every last one i had in some cases and then had to wait for another shipment. so they came from a few different places and could have gotten mixed up.

and these color codes are hard to read sometimes. once i found it impossible to distinguish brown from red on resistors from different suppliers. this way i mixed up 10k and 100k...
since then i found it more functional to check the value of the resistors before i solder them (at least one of a batch).

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para



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PostPosted: Wed Apr 25, 2007 11:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

thats a good idea. i should try and get in the habit.

this is pretty handy, i think i found it through someone's post here, i spend a lot more time reading here then i do typing:

http://www.schematica.com/resistor_color_codes/Resistor.htm
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State Machine
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PostPosted: Thu Apr 26, 2007 4:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
you think i should just focus on the section that you mentioned before?


Sure, check R53. Should be 1 MEG .... Br - Bl - Grn .... Very Happy Very Happy

Let us know.

Bill
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para



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PostPosted: Thu Apr 26, 2007 4:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

its correct.
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para



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PostPosted: Fri Apr 27, 2007 9:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

you know bill, i halfed all of my input control resistors and my tempco is a 1K i got from Bugs' group buy, could that be doing anything?


i guess i completely forgot to mention that HUGE change i made.



steven
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fonik



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PostPosted: Sat Apr 28, 2007 6:16 am    Post subject: Reply with quote  Mark this post and the followings unread

para wrote:
you know bill, i halfed all of my input control resistors and my tempco is a 1K i got from Bugs' group buy, could that be doing anything?


i guess i completely forgot to mention that HUGE change i made.



steven

that's exactly what i did. and it works fine as supposed to. this could do no harm as you keep the ratio of the input resistors (R33, R34, R35 and R61) and the tempco (R7) in the feedback path.

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para



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PostPosted: Sat Apr 28, 2007 1:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks matthias, thats good to know i didn't mess that up. those are exactly what i changed as well. i did the same on my XR's and they are fine.
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