Subatomic's fabrication journal for #121

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subatomic
 
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Subatomic's fabrication journal for #121

Post by subatomic »

Hi people, I've finally started soldering, so here's the worklog so far.
Feel free to post comments or questions...

http://www.subatomicglue.com/x0xl0g
Last edited by subatomic on Mon Nov 07, 2005 4:13 pm, edited 2 times in total.

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subatomic
 
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potential problem.

Post by subatomic »

I've completed the PSU and VCO and
I came into a potential problem with the VCO:
- seems the pitch is kind of jumping around when I probe the circuit.
- also, the VCA readings of the waveforms are off from the fab manual.

It might be nothing, but I thought I'd ask.
You can read all the details and measurements about this problem in my x0xl0g.

If you have an idea about whether this issue is really a problem or not please let me know,
I'd rather fix it now before moving on...

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subatomic
 
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Re: potential problem.

Post by subatomic »

subatomic wrote: - also, the VCA readings of the waveforms are off from the fab manual.
Someone in another thread answered this, apparently I have an RMS meter and forgot to take that into consideration when doing my measurements (doh!):
Guest wrote:a multimeters vac setting usually measures
the rms value not the peak to peak value
rms for a sine wave is about one third the peak to peak value
this is most likely the reason for the reduced meter readings
So that's good, at least one of that's not a problem.

So that leaves just one more (possible) problem:
subatomic wrote: - seems the pitch is kind of jumping around when I probe the circuit.
What do you think? Ever seen the pitch jump around when testing the VCO?


From my worklog:
subatomic's x0xl0g wrote:Second potential problem: Am seeing some instability at times where the waveform jumps up an octave or so. Not sure why, but it seems to happen unpredictbly, only when I'm touching a lead to the waveform selector switch (the place you test the signal), or touching the switch (interface end) with my fingers. If I attach the lead and leave it all alone, it seems to stabilize to either the low or the high pitched waveform (doesn't seem to settle-to/prefer either one).

So the question at this point is: are these real problems, or just the product of testing. Is it something that will stabilize when I'm not poking around the circuit?
Last edited by subatomic on Mon Nov 07, 2005 4:03 pm, edited 3 times in total.

evilxsystems
 
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Post by evilxsystems »

I have the same problem...I think it is due to the headphones loading down the circuit...I just decided to hold off on the tuning until I get the whole thing built and can easily give it the exact voltage and monitor the sound more easily. I also can't hear my resonance...I can tell my cutoff is working but I can hear it resonating....I'm hoping that's also due to bad (ie too good) headphones.

-jason

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Post by Guest »

unless you have a test voltage applied to the
input of the vco
it will float around and change randomly
causing the frequency of the vco to change randomly

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Post by djarago »

rms voltage for a sine wave is divided by sqrt(2) of the peak value

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Post by subatomic »

Anonymous wrote:unless you have a test voltage applied to the
input of the vco
it will float around and change randomly
causing the frequency of the vco to change randomly
Haven't attached the 2VDC/3VDC CV for testing yet because I was going to wait until the seq section was built so I could simply press buttons. :wink:
I hadn't expected the floating behavior, but it makes sense now. :oops:

Thanks everyone, so my VCO and PSU are good.
Time to move on to the next step :D

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VCF results, cutoff good, resonance not sure...

Post by subatomic »

I just completed the VCF section, and am testing resonance and cutoff. The FabManual just says "probe the potentiometer". But it doesn't say which pins to probe, so I tried them all...

On pin 1 of VR4 (looking from the top, leftmost pin), I'm getting a great cutoff sound as I twist VR3.

On pin 6 of VR4 (from the top and rightmost pin), I'm getting weird results when I twist VR4, it seems that 90% of the range of the pot yields no change in sound, then in the last 10% the sound snaps on and I can kind of hear it change, but it isn't acidic (but that may be hard to hear).

On the other pins, I'm not hearing anything at all, but I'm assuming that's normal.

Again, I'm not providing a voltage, so it's floating (I'm getting random pitches). Could this be my problem. Or am I probing the wrong pin? Or something else? By the way, TM3 is centered...

thanks,

ps.. Could someone update the fab manual with what pins to probe? :)

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Post by memology »

The Kester 63/37 solder arrived today as well. It has a lower melting point and a faster state change than other solders (narrower band of temperature range for liquid to solid transistion), so should be easier to work with than the recommended 60/40 solder. 63/37 changes from liquid to solid in a 0deg band (instantly) while 60/40 has a 13deg band where it is pasty before solidifying..
You still might want to consider using 60/40 for some components like pots, switches, ICs - that "13deg band where it is pasty before solidifying.." could be very useful if you ever need to remove or replace things that have multiple solder connections.

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Re: VCF results, cutoff good, resonance not sure...

Post by subatomic »

heh, I was just about to delete my post when you posted, memology. I just realized my mistake. I used the 1M pot instead of the 50kb.
memology wrote:could be very useful if you ever need to remove or replace things that have multiple solder connections
I think you have a spy cam at my workbench somehow. :) so yes, I will have to unsolder it. But fortunately I use 60/40 for all the "big" parts, like pots and such since I have a 1lb of it, and only 1/2lb of the 63/37... Using 63/37 for sensative stuff like transistors.

oops. :oops: :cry: figures the one thing I'd mess up on would be the pot with the most pins and huge solder joints. :roll:

My recovery strategy... I'll probably try the solder sucker first, then solder wick, and then finally trying to melt multiple at once. Soldersucker might not be too bad since I can melt from either side of the board with the solder sucker on the other side for full sucking power. I'm optimistic. Will resume tonight...

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ba6110 replaced, x0x r0x now

Post by subatomic »

status update:
got my ba6110 in the mail this weekend. x0x makes sounds now out the headphone jack. pretty fun.
Still need to solder in the LEDs and put it all in the box...

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Post by experimental »

Thank you for the update-

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subatomic
 
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121 works

Post by subatomic »

121 works, been sequencing some fun stuff this morning.

I noticed a potential bug and wondering if it's fixed in the latest firmware (sf.net is down right now so I can't try an update).

I don't know how it happened, but the x0x got into a bad state in Pattern Edit mode where none of the 16 sequencer LEDs would light while I'm pressing Prev and Next (normally these would show you which note in the pattern you are currently editing). I got the LEDs to shine again after connecting the USB, after which they light while pressing prev/next showing me what slot is currently being edited... It's very difficult to edit notes when you don't know where you are in the pattern! :)

Not sure why plugging in USB would fix it, but I'm guessing it's a side effect...

Anyone else get this before? Will the latest firmware fix it? Everything seems to be operating very normally otherwise. Very fun.





Background:
I believe what I was doing right before the lights stopped showing was this:
- I remembered I had to hit "Done" to save my pattern. So while the cursor was on slot 1 I hit the Done key. This screwed up the pattern so that 1 was the ending of the track, track was now 1 note long. After being confused and screwing around to see what I did wrong (pressing buttons and turnings the mode knob) I noticed that the prev/next didn't light up the 16 seq lights anymore....

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