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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Why is my Lunetta not working?
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electri-fire



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PostPosted: Wed Apr 07, 2010 10:14 am    Post subject: Why is my Lunetta not working?
Subject description: An inventory of problems you may encounter and their solutions
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Why this topic?

I've been into building Lunetta's since late summer 2009, when I acquired an assortment of electronics parts, including more than a hundred CMOS chips.

I've encountered problems, did research, found strategies to cope with some weird malfunctions, have been helped by fellow forum members.

A guide on building Lunetta's has been written by droffset. Last time I read it a troubleshooting section has not completely materialized.

Here's a place to discuss your issues, hints and tips on getting your Lunetta to work as you expect it to.
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electri-fire



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PostPosted: Wed Apr 07, 2010 10:54 am    Post subject: Cleaning off the resin / flux after soldering Reply with quote  Mark this post and the followings unread

Using solder flux and resin core solder greatly facilitates soldering. sure that's true.

Some manufactures state these additions/ products enhance the reliability, "protecting" and "isolating" the solder joint.

IT IS A LIE!

Solder flux is an acid that cleans your board by etching away the top layer of copper. But is doesn't stop etching after soldering.

The resin from your solder is in fact a conductor creating shorts.

Les Hall (inventor) was the first to point this out to me when I took my non functioning Lunetta with me to the EM2009 meeting.
I had checked a hundred times for mistakes, cold joints, and solderbridges to no avail. Les got it working for me by cleaning the circuitboard.

For this we scraped away the resin between the traces and dissolved it with vodka, as this was all cleaning agent available.

I've seen people using "rubbing alcohol", and there's dedicated products for this purpose available (recommendations welcomed here).

I use scrapers like a mini screwdriver, a dental probe, and a metal wire brush first, then a stiff shorthaired brush with 100% alcohol, wich is what I happened to have in the medicine cabinet. But like stated above, some sort of solvent will likely do the job.

Do not underestimate this. More than once or twice, eager to try my latest solder achievements, I tested first without cleaning and not have it work until after meticulous scraping and cleaning the board.

I'm not talking solder bridges here. I measured resistance of near zero ohms between traces that had nothing but the solder core resin between them.
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PostPosted: Wed Apr 07, 2010 3:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've never cleaned my boards in any way, and I've never experienced one of them "not working" due to anything I could fix by cleaning them. It has always been a wrong component, wrong orientation, solder short, or, far more often, a fault in the interconnections to the controls.
I'm not saying that it's not possible that resin will act as a partial short, I just know that my boards are covered in it, and it has never caused a problem.
As for flux,......!?!?
I can't understand why anyone would use flux on electronics. Plumbers use flux when they're soldering guttering together! If your parts and board are clean, and your iron is at the right temp, (around 280-300 deg in my experience) you don't need to eat the surface away with flux to make a good solder joint.
All that being said, I do plan to try out the "clean the resin off" theory on a VCF which, although it "works", doesn't sound as sweet as I think it should. The potential for resin to increase stray capacitance is probably a lot more of a problem than partial shorts, and this would be more critical in the resonance path of a VCF than anywhere else. (IMHO)

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PostPosted: Wed Apr 07, 2010 3:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yup, don't use flux and resin is not a problem except for few critical spots, such has been my experience too.
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electri-fire



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PostPosted: Fri Apr 09, 2010 5:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Hmm, I'm wondering why I would be the only one with this problem. I do not etch PCB's, so working on perfboard may have something to do with it. With all these in/outs on a single IC I have lots of tracks adjacent to each other.

That sucks, to be honest. I have solder bridges a lot. Diagonal cutters , small files and scrapers, a desoldering pump, solder wick and even dental burs I have been using to deal with these.

But I'm like 95% certain of multiple occasions where the sole problem must have been the solder resin. Am I turning crazy here?
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PostPosted: Fri Apr 09, 2010 10:57 am    Post subject: Reply with quote  Mark this post and the followings unread

electri-fire wrote:
Hmm, I'm wondering why I would be the only one with this problem. I do not etch PCB's, so working on perfboard may have something to do with it. With all these in/outs on a single IC I have lots of tracks adjacent to each other.

That sucks, to be honest. I have solder bridges a lot. Diagonal cutters , small files and scrapers, a desoldering pump, solder wick and even dental burs I have been using to deal with these.

But I'm like 95% certain of multiple occasions where the sole problem must have been the solder resin. Am I turning crazy here?


I don't think so.
I haven't built a Lunetta yet, but I have done a bit of PIC stuff. The last one was a knightrider sequence on stripboard and before the flux was cleaned off properly, there would be some random flickering when a certain LED should have been lit. Once the board was fully cleaned, the flickering disappeared......
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PostPosted: Sat Apr 10, 2010 2:23 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't think it's a perfboard or stripboard thing. The SoundLab I built is a stripboard layout, it's quite big, and is jam packed full of components, uncleaned, and worked perfectly first try. Confused
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PostPosted: Sun Apr 11, 2010 11:57 am    Post subject: Reply with quote  Mark this post and the followings unread

So I'm going from breadboard to perfboard, any suggestions, things to look out for, etc?
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PostPosted: Mon Apr 12, 2010 4:40 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm assuming that you're using CMOS.
Only the usual warning about tying all inputs low or high through a 100K resistor. Depending on what you want their default input to be.
And put a 100nF decoupling cap across every chip's power pins as close as possible to the pins.

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PostPosted: Mon Apr 12, 2010 7:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
I'm assuming that you're using CMOS.
Only the usual warning about tying all inputs low or high through a 100K resistor. Depending on what you want their default input to be.
And put a 100nF decoupling cap across every chip's power pins as close as possible to the pins.


Ok, I think that sums it up nicely for now:

Pulldown/pullup resistors, decoupling capacitors, and cleaning if all other troubleshooting fails.

On perfboard/stripboard: I've used board with three holes attached, didn't like that much. Now I used board with single copper pads (just because I had them).
The advantage of these is you don't have to cut traces. The disadvantage is you need to connect traces. duh. When buying new board I "think" I'd prefer copper strips and cut where needed. I haven't tried that yet though.

A bit off topic:
As I'm making a non frontpanel Lunetta now, I've arranged IC's next to each other that are most likely to be connected. 40106 oscillators central, 4040's next to those, then, (if I'd use gates, but this time I wont) I'd have those around the cluster of osc's and 4040's. Further from center come the multiplexers like 4051, the shift registers (I'm having 4015 and 4021), next the R/2R networks. At the edge of the board close to the output are my "VCO's" (VC powered 40106, maybe 4046 or xr2206, but I'm running out of room).

Ok, enough electri-fire spam for now. Have fun.
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PostPosted: Mon Apr 12, 2010 8:24 am    Post subject: Reply with quote  Mark this post and the followings unread

electri-fire wrote:

On perfboard/stripboard: I've used board with three holes attached, didn't like that much. Now I used board with single copper pads (just because I had them).


I kind of like that proto-board with several holes attached for Lunneta circuits. It's rare that you need more than that for a leg of an IC and it's easy to work with.
I've used LOTS of bare perfboard - no copper at all - it's a bit of a pain, but I'm used to working with it.
I don't care much for the single copper pads - but I'll use it if I've got it.
I recently got a truckload of stripboard (well, a bunch of it) in a purchase of parts from a guy...but I have not tried it yet.

That's my 2 cents on the subject....

bruce

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PostPosted: Mon Apr 12, 2010 8:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Just a noob's $0.02 on stripboard vs. perfboard: I prefer perf. In theory, I thought stripboard would make things easier and require fewer jumpers, but in practice I found it harder to follow what was connected where. Especially when it comes time to figure out why something isn't working, I find it easier to only have to follow traces I put there, instead of trying to find a place I should have cut but didn't (or vice versa). Of course, ymmv.
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PostPosted: Mon Apr 12, 2010 11:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey, nice blog slugger!
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PostPosted: Mon Apr 12, 2010 11:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey, just caught this thread... It was fun to fix Mathe's Lunetta with Vodka at EM09, and I must mention that the reason this was an issue is because there were lots of teeny metal fragments in the flux.

Flux itself is an insulator and will not mess up low frequency circuits like our audio stuff. It is, however, a glue-like magnet for any metal filings that happen to float around and that's what creates the shorts or resistive connections between nodes.

It was a joyful sign of things to come when we fixed Mathe's Lunetta with Vodka, as the three days of paradise had just begun, lol. I wonder what else I can fix with vodka... my attitude perhaps...

Oh yeah, a note on cleaning flux with any alcohol - you must wash it off the board, not just stir it around on the board. Put some on, brush it around, then flush it. That'll do the job.

Les

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PostPosted: Mon Apr 12, 2010 11:45 am    Post subject: Reply with quote  Mark this post and the followings unread

electri-fire wrote:
Hey, nice blog slugger!


Thanks, electri-fire!

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electri-fire



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PostPosted: Mon Apr 12, 2010 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
A note on cleaning flux with any alcohol - you must wash it off the board, not just stir it around on the board. Put some on, brush it around, then flush it. That'll do the job.


Yes, when you just dilute it and let it dry you've done nothing. I scrape, brush with alcohol, then dab off with a tissue, brush with more alcohol, soak it away with a tissue again.

I've read people wash with soap. I've seen written distilled water would be preferred as tap water is corrosive. Ah well, alcohol works for me.

Metal scraps in my solder resin?. Hmyeah, I have used files or burs sometimes to deal with solderbridges. But not always I think. At any rate, the solution has been to clean, metal filings or not.
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PostPosted: Mon Apr 12, 2010 12:29 pm    Post subject: IC Sockets Reply with quote  Mark this post and the followings unread

Tried everything and still flabbergasted? Doubt creeps in. Did I overheat when soldering? Did I fry the chip with static discharge?

You'll be happy if you used sockets for your chips.

It prevents overheating while your soldering skills are developing. It will save you desoldering your IC's in desperation. This would be extra frustrating if it's in vain because you overlooked something (again and again and again). As Andy mentioned, the latter is indeed the most common cause of malfunction.

.
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PostPosted: Fri May 14, 2010 11:47 am    Post subject: Reply with quote  Mark this post and the followings unread

How necessary is the pulldown resistor thing, in your experience... and could you explain a little more about where they would be used?

I am about to perf this project I am working on - mentioned in the simple arpeggigator thread. It has 4093 oscillators gated by a 4017. Would I put the 100k resistors before all of the inputs on the 4093's?

And then... does that mean I put them also on the clock input for the 4017,

And lastly, would they also go between the power source and input to the power to the chips?

Will the chips trigger if they are running off of 12V (without resistors), for example, but the triggers have 100k resistors before them?

I am planning on putting in sockets for sure... definitely worth it, in my past electronics building experience. I have never ruined a chip by over heating it, but I have had chips fail on occasion. A 30cent chip is cheap if it blows - not a big problem, but it becomes a big problem when you have to desolder and resolder 14 or 16 pins only to find out that the new chip doesn't fix the problem.
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PostPosted: Fri May 14, 2010 1:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Top Top wrote:
How necessary is the pulldown resistor thing, in your experience... and could you explain a little more about where they would be used?
This /../ project has 4093 oscillators gated by a 4017. Would I put the 100k resistors before all of the inputs on the 4093's?

And then... does that mean I put them also on the clock input for the 4017,


Pulldown (or pullup) resistors are more important when inputs are left unconnected, as in a patchable section of your Lunetta. For fixed connections like your 4017 clock, maybe there's need for them. I use no pulldowns for fixed clocks or other inputs, works.

I had a 4093 in my former (now abandoned) Lunetta with spdt switch between "Hi" or "external input", but next time for a 4093's I'll try pullups instead of pulldowns as in theory without a modulator at the "Gating Input" should default to the "on" state.
Erm... in short, decide for pullup or pulldown according the state you want your input to default to when unconnected.


Top Top wrote:
Will the chips trigger if they are running off of 12V (without resistors), for example, but the triggers have 100k resistors before them?

I've seen that in schematics, so I "think" they will.

Top Top wrote:
And lastly, would they also go between the power source and input to the power to the chips

I have seen schematics with smallish resitors in the powerline to "reduce power use and noise" , 100 or 200 Ohm up to 1K, never seen higher. I don't do that though, I might try sometime.
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PostPosted: Fri May 14, 2010 1:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

electri-fire wrote:

Top Top wrote:
Will the chips trigger if they are running off of 12V (without resistors), for example, but the triggers have 100k resistors before them?

I've seen that in schematics, so I "think" they will.


I had wondered about this as well for adding a clock divider to the mixed output of a few 4093 oscillators (to get lower octaves quickly). I wasn't sure if they would be strong enough to move it if they've been mixed through resistors. I can always just throw one on the breadboard and try it out.
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PostPosted: Fri May 14, 2010 2:28 pm    Post subject:
Subject description: feeding a mix into 40932 inputs
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Top Top wrote:
electri-fire wrote:

Top Top wrote:
Will the chips trigger if they are running off of 12V (without resistors), for example, but the triggers have 100k resistors before them?

I've seen that in schematics, so I "think" they will.


I had wondered about this as well for adding a clock divider to the mixed output of a few 4093 oscillators (to get lower octaves quickly). I wasn't sure if they would be strong enough to move it if they've been mixed through resistors. I can always just throw one on the breadboard and try it out.


just thinking again:
The 4093 is a Schmitt-trigger inverter, meaning it will sense a "Hi" once a certain voltage is exceeded. But then, all inputs do that I think, ignoring sub threshold voltages.

suppose with for instance four mixed inputs, just one is Hi, and this wouldn't meet the voltage standard for a Hi signal. Would more Hi's occuring simultaniously lead to higher voltage when mixed through resistors? It works with a 40106 I have that gets the + voltage from an R/2R DAC. I don't know how say, a 4040 would react, mine are all hardwired to fixed clocks.
You may have to tweak resistor values or use an opamp buffer. Or hey, maybe try a "Depth" pot to see if you can get some influence on the number of "Hi" 's required to exceed the threshold.

You won't get the exact 4093 mixed outputs devided down, just the peak signals of the joint outputs. Maybe adjustable?
It's an interesting issue, so I'm curious for your results.
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PostPosted: Fri May 14, 2010 2:49 pm    Post subject:
Subject description: feeding a mix into 40932 inputs
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electri-fire wrote:

just thinking again:
The 4093 is a Schmitt-trigger inverter, meaning it will sense a "Hi" once a certain voltage is exceeded. But then, all inputs do that I think, ignoring sub threshold voltages.

suppose with for instance four mixed inputs, just one is Hi, and this wouldn't meet the voltage standard for a Hi signal. Would more Hi's occuring simultaniously lead to higher voltage when mixed through resistors? It works with a 40106 I have that gets the + voltage from an R/2R DAC. I don't know how say, a 4040 would react, mine are all hardwired to fixed clocks.
You may have to tweak resistor values or use an opamp buffer. Or hey, maybe try a "Depth" pot to see if you can get some influence on the number of "Hi" 's required to exceed the threshold.

You won't get the exact 4093 mixed outputs devided down, just the peak signals of the joint outputs. Maybe adjustable?
It's an interesting issue, so I'm curious for your results.


My thoughts were that it would not handle mixed notes well for sure (more than one osc at a time) - it would probably be like playing chords into an octave pedal... The thought was, however, that this could also be useful for more easily producing percussive/noise types of sounds without a lot of other fancy modulation options.

But the main issue I was wondering was if the divider would trigger/divide at all with outputs that have had the voltage reduced by the summing resistors, even if they were only one oscillator playing at a given time.

Some of the other stuff you mentioned flew over my head... for lack of understanding of logic/electronics/cmos, I am sure...

My plan was to try a 4040 to divide the outputs of the 4093's.

I don't think that the added voltage output of more than one output would be more than 12V if it is powered by 12V, but I am not sure... it just doesn't make sense to me that it would be fed by one 12V supply but the chip would be producing more than that (conservation of energy and all that), but I could be wrong.
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PostPosted: Fri May 14, 2010 10:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok well I tried and the 4040 will not clock a source from after a 100K resistor when running at 12V.... makes me wonder how one could divide from more than 1 input source or if it is possible at all? Maybe smaller value resistors (will try it).

I tried putting a 100K between the + voltage and the power input pin (to see if running on the same voltage as the clock input would change anything - just a wild guess), and that didn't help.

Edit: tried using 10K resistors - it would trigger the 4040 with just one osc through a 10K, but as soon as they were mixed with 10k's it no longer worked. Tried the same thing with 1K's same deal... Maybe need a buffer or something to pull the current through...

anyway, maybe this discussion in general belongs in a different thread...
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PostPosted: Sat May 15, 2010 6:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
I'm assuming that you're using CMOS.
Only the usual warning about tying all inputs low or high through a 100K resistor. Depending on what you want their default input to be.
And put a 100nF decoupling cap across every chip's power pins as close as possible to the pins.


I'm very curious (and not knowing) here.

In my latest device - the Atari Jazz Console V2 - I've got clock crosstalk going on. Now - I've assumed it could be due to the 4023's and 40106's used, having multiple clocks within each of them, possibly effecting each other.
I DO have 0.1uF caps for each chip. COULD, the fact that they're each 3 to 5 millimeters away maximum, make THAT much difference?
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PostPosted: Sat May 15, 2010 4:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Top Top wrote:
anyway, maybe this discussion in general belongs in a different thread...


Ok, I've relocated.

http://electro-music.com/forum/post-295511.html#295511
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