n0nx0x2 build (problem solved, finished!)

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Grimoire
 
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n0nx0x2 build (problem solved, finished!)

Post by Grimoire »

Hello all,

I'm new to synth building but have done my share of other diy projects like high end speakers and amps

Now I'm building nonxox2 with custom front panel (group buy)
Xoxbox kit bought from willzyx without cpu and front panel

I already soldered the saw, and square generator and filter which worked fine (soundcard probe tested). Voltages also measured fine.

The envelope tested 12V on D35 but couldn't measure the short peak at D36 (saw a small change on my multimeter, but doesnt have a hold function)

Then I soldered the VCA and tested it, but there was no note to be heard from the headphones probed on right VR8 pin-hole (components side of the print) The left hole produced a low frequency buzz.

Anyone have a clue what's wrong here?
(Tried to use the search function but couldnt find an answer)
Last edited by Grimoire on Sun Jun 22, 2014 1:56 pm, edited 2 times in total.

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antto
 
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Re: n0nx0x2 build (gate problem?)

Post by antto »

the signal at D36 is a very short impulse, something like 1ms or so
it's purpose is to retrigger (charge) the envelopes
such things can't really be measured with a simple multimeter (unless it's a more advanced one)
so don't worry about it that much

for that specific test (D36) you could use the headphones technique or record with a computer (soundcard) and see if you got a short impulse... but beware: the signal there goes as high as 12V (for a short moment) so don't hook headphones/soundcard directly, but thru a resistor!
i probe with my soundcard usually with a 100k resistor in series
if you're probing with headphones - you should hear a very very short/sharp "pop"

now, for the other test - the VCA
the VCA may work properly and yet you may not hear anything if:
- the VCO is oscillating at some very low or very high frequency (which may happen if you don't provide some sane control voltage)
- the VCF cutoff freq is down very low (so make sure you set cutoff/envmod/decay to max)
- the volume envelope doesn't get triggered for some reason (the build manual instructs you to manually trigger it)

also check if you're probing the right pin on the volume pot, one of them is connected to ground..

Grimoire
 
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Re: n0nx0x2 build (gate problem?)

Post by Grimoire »

Thanks for the advice,
I figured its indeed best not to worry and go on with soldering the other parts
Maybe its working fine... Will get back here later with an update on what works and what not!

Grimoire
 
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Re: n0nx0x2 build (gate problem?)

Post by Grimoire »

Finished the build,
But unfortunately no sound (from headphones)

Like I wrote above I failed the gate test, so I assume something went wrong there. Any voltages I could specifically check?
Saw and square generator worked, also resonance and cutoff from the filter.
Solder joints seem fine

Before I put the microcontroller in I checked if there were no strange too high voltages that could possibly do damage.
Machine starts up, all the leds seem to work, and at certain settings i can get the 1-16 bar to run when I hit play. So I tink that part works
No sounds from pressing the 'keyboard' keys at any setting

Grimoire
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by Grimoire »

will start with the eagle voltage file to check things

any tips and suggestions are very welcome:)

Grimoire
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by Grimoire »

Measuring 6.2 and 1.9 mV at R146

Should be double of that according to the eagle file?

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antto
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by antto »

on one side of R146 (towards the cpu) you should have either 0V or 5V depending on whether a note is ON or not (5V when ON)
but if the sequencer is playing patterns - it would be hard to get a sane reading on a multimeter

if you have a recent version of n0nx0x there - switch to Pattern-Play mode, make sure the sequencer is not running, and press TAP - this would trigger an infinitely sustained note (test-tone) so then the gate (R146) would be high all the time, and you'll be able to measure 5V then (hopefully)

if you don't have a recent version of n0nx0x - switch to KEYBOARD mode instead, and hold one of the keyboard keys (any) to get a sustained note (but you'll have to hold it down while measuring)

Grimoire
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by Grimoire »

Sorry couldnt edit post on ipad (captcha not showing)

Measuring 6.2 and 1.9 mV at R146 ( should be double)
2v at R137 and on negative side of d34

Double voltage on J6 pin 3 (1.8V)
Low voltage on J6 pin 1 (0,6V)

Grimoire
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by Grimoire »

Running the newest beta i think, just got the chip!
if you have a recent version of n0nx0x there - switch to Pattern-Play mode, make sure the sequencer is not running, and press TAP - this would trigger an infinitely sustained note (test-tone) so then the gate (R146) would be high all the time, and you'll be able to measure 5V then (hopefully)
It works, I measure 4,94V :)

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antto
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by antto »

okay, so the cpu outputs gate properly

what voltages do you get on R133?

Grimoire
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by Grimoire »

2.6v and with gate open (like above) 11.5v

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antto
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by antto »

okay, measure the voltage on pin1 of IC15A (if you have BA6110, then IC15A would be empty)
see if the voltage there peaks at something like 0.5V when playing a note, and then decays to 0V

Grimoire
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by Grimoire »

Thanks for thinking with me here!

Tried it, and voltage seems already around 0.5v without hitting a note at pin1 of ic15a (im using ic15b)
When I hit a note it peaks (when i hold a note it is 8,5v) and gets back to around 0.5v but never to 0v

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antto
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by antto »

damn, i think my multimeter is fooling me, one of the probes doesn't make good contact some times

check the voltage at C41 (on the positive side) that should be a bit more reliable place to check for the volume envelope
it should peak at 320mV and decay to 0V on note ONs

also, check the voltages of the BA6110 against the reference map, and the orientation, the "notch" on the chip should point up towards the pots

if none of this helps - start looking closely at the components in the VCA section, see if any of them are wrong value, or wrong orientation, also check the solder joints for any visible issues

i'm kinda running out of ideas...

Grimoire
 
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Re: n0nx0x2 build (with regular xox kit. gate problem?)

Post by Grimoire »

I think the south pole of the C41 cap is what you mean with the positive side. There I get a pulse when hitting a key to about 440 mv then back to 0v (havent tuned the xoxbox yet by the way)
And the voltages on the BA6110 were correct.

So everything seems to be working so far, but still no sound trough the headphones (will check other output later)

Good idea to check VCA components and orientation on them tomorrow. Hopefully I'll find something

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