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WIGGLING 'LITE' IN GUEST MODE

My Weston Audio 2VL1 Build Diary
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2  Next [all]
Author My Weston Audio 2VL1 Build Diary
wendallsan
Hi all,

I'm building a pair of Weston Audio 2VL1's and figured I'd document the process.

The module consists of 2 VCO's and 1 LFO in a 3 board, 10hp design, so it's a little module with a lot of functionality.

The components are easy to source, I was able to amass everything with an order to each of Thonk, Tayda, and Mouser.

The documentation is super detailed compared to what I've had on other projects-- there is literally a 20 pages manual put together by the creator that is very thorough. The boards seem well laid out and have nice, think traces on them so chances are better that I won't jack up a thin solder trace during my building.

This is the first PCB I've worked with that has components listed by number rather than value, which slowed me down a bit at first, but I think I like this approach as you know exactly what point something should be and there's less finding you still have an extra resistor once you've thought you've put everything into place. I'm happy my first builds didn't do this, though, as that taught me how to read resistor and cap values better. I'm sure that this is second nature to most folks here by now, but it was nice for a beginner like myself. Labels are clear and anything not obvious on the board (the polarity of a tantulum cap, for instance) is well explained in the documentation.

I was able to assemble the 1st board so far without issue (as long as I can find where my last IC's for this board went ...). Looking forward to having the next board together and another update in a day or two.

devinw1
Dang you're fast! Guinness ftw! SlayerBadger!
wendallsan
An update and more pics!

I finished building the second boards and realized that the top-most boards are pretty much solid pots and jacks, so those were easy boards to throw together compared to the other two.

Initial tests didn't go well, but I never expect things to work out of the box. hmmm.....

The first module's LED's lit up, the LFO worked, but the VCO's did not, and 2 of the chips on the bottom board were getting hot.

The second module emitted a pop and a foul smell when plugged in, so I probably burned something out. Dead Banana

The smell seems to come from the group of caps at the middle of the bottom board-- not sure if its one or both sides.

I'll be troubleshooting these soon!

My updated thoughts on this build are that these are HEAVY and SOLID modules. The faceplate is about twice the thickness of others that I have in my collection, and the assembled modules have a very weighty feel. The PCB's are also extra thick, a very nice solid construction. The board makes use of two-row headers between boards in some clever configurations, and the 2 lower boards are densely packed. The build has been very easy and the instructions are clear on all things but the orientation/polarity of the LED's on the boards, but that was a good homework assignment for me to see if I could read the schematic.

I picked up a copy of the "How to Diagnose and Fix Everything Electronic" book and am reading through that in hopes I'll start to grasp the process of troubleshooting circuits that are misbehaving.

More Pics of these modules coming together:




devinw1
Ah crap, 0 for 2!! We'll get it sorted tho.

On those chips getting hot, please triple check the orientation of all the Ics. I know it seems stupid bit I've put an op amp in backwards once or twice myself and gotten toasty! The silk screen notches should be visible even with dip sockets so you can check against that thumbs up
wendallsan
devinw1 wrote:
Ah crap, 0 for 2!! We'll get it sorted tho.


I checked the IC's and "shore 'nuff", one of the bigger ones was inverted on the VCO that had been popping and smelling bad when plugged in. A quick check of it resulted in the same results as the other VCO: the LFO worked, but the VCO outs didn't seem to be doing anything. I wiggled some knobs and presto-- waveform achieved. The pots full to the left just don't make any audible sound, of course!

With that discovery in mind, I checked the other module's VCO's and yup, all I needed to do was turn the knobs to find that the VCO's were working!

Wow, that was waaaay to easy of a troubleshooting project, I didn't even get to ask any questions !! seriously, i just don't get it

But these modules are working and ready to calibrate! nanners
wendallsan
Finished shots! Ready to calibrate! It's peanut butter jelly time! It's peanut butter jelly time!


devinw1
Yessss! Nice one! The old flipped chip will get ya every time!

And yeah, the coarse tuning knob has a pretty huge range, so with no CV going into the 1 V/oct jack, you can take it down into the "no sound" range basically.

BTW looks cool with the non traditional knob color scheme!

SlayerBadger!
wendallsan
Which trims are which on the module? They're not labelled and I don't think that is actually documented (maybe in the schematic?) ... or if it is I've failed to find it! help
devinw1
They are labeled on the back side of the boards, if you peek in there you can see the ones on the middle board, but the ones on the back board should be pretty visible. The 1 V/oct and Hi Freq trim for each VCO will be on the back board on the corresponding side as where the knobs are for that VCO.

The middle board has the saw shape trims for each VCO on it, again lined up with the side that corresponds to the knobs for that VCO.
wendallsan
devinw1 wrote:
They are labeled on the back side of the boards


d'oh! d'oh! d'oh!

Foiled by the board having two sides!
wendallsan
That VCO Tuner app you mention in the calibration instructions seems very cool! I'm trying to use it to calibrate my VCO's.

With Resolution set to "quick and dirty" and pitch range set to narrow > coarse, I get 3 "bands" of info to tune by. I can't seem to get all 3 lines to "line up" using just the VCO VOLTS/OCT trim. I can get one or the other pretty well 'dead on', but then the other band is off by 5 cents or so. Is there a solution for this-- for example, would adjusting the HF FREQ trim help with this?

Here is what I'm currently looking at:



Can't wait to try this on my other VCO's as well once I've got it figured out!
devinw1
Despite having mentioned that app in the build notes, I haven't actually used it much, but make sure your tuning knob is to a point where the app isn't operating in a crazy low regime or something. It may not recognize super low frequencies (or really high ones) very well. When I tune manually I like to go from C1 to C4 or 5, then pop over to C8 (4.1khz) and C9 to check high frequency trim.

Anyway, manually with logic pro's tuner I usually don't see anything worse than 2-3 cents so you're not far off. It may be fine. Again not too familiar with the app.

Btw as I mention in the guide, so many tuners have trouble with high frequencies (above C7 or so). I find my o scope's hardware frequency counter (and my ear) to work better. For example if I set my C8 to 4186 Hz via the scope, and it sounds good to me, often Logic's tuner and the other 3rd party tuner I have will start flipping out and saying it's an F or something . Hah
wendallsan
They are in the rack!

Clearly the most colorful modules to date. Seriously tempted to buy and build two more to make a PRIDE oscillator bank.

Hopefully will have some time tonight to get them into a patch and humming!


devinw1
Sweeet! SlayerBadger!
wendallsan
Oh no! screaming goo yo

Somehow, somewhere between my test bench and the rack, my "orange" oscillator has stopped it oscillating. VCO2 on my 1st module is now outputting a constant +5V signal when its frequency knob is between fully CCwise and about 2 o'clock position, and then outputs a constant -5V signal when its frequency is adjusted above the 2 o'clock position. This seems to be occurring on both the saw and square wave outputs. I can also get this voltage flip to occur using the PWM pot and the square wave output-- turning it above 12 o'clock sends the voltage high, turning it down sends it low. VCO1 and the LFO are still both working fine.

Any suggestions on where to start testing things to get this oscillator back online? hmmm.....
devinw1
Hmmm. Perhaps a dumb question but have you got the sync switch clicked in the middle (off)?
wendallsan
devinw1 wrote:
Hmmm. Perhaps a dumb question but have you got the sync switch clicked in the middle (off)?


Hi and thanks for the assistance!

Sadly, no, the problem isn't that simple. The switch was the first thing I tried as well when I noticed that nothing was coming out of the oscillator.

Turning on the Sync switch so that VCO 2 syncs with VCO 1 results in some weird waveforms, but not what I would expect to see. This creates a very narrow pulsewidth waveform that is either high or low, but adjusting the frequency knob on VCO 2 doesn't change much else, and the high/low switching point is the same point that the voltage goes high or low when sync is disabled.
devinw1
OK, yeah that shouldn't make a difference now that I think about it, but just wanted to make sure you checked the obvious stuff first hihi .

If you're sure all the solder joints are good and everything is connected OK, the first think you could try swapping is the LM13700, as it is possible half of it got blown somehow. Do you have an extra 13700 to swap in? Do be careful as those chips are fairly ESD sensitive.
wendallsan
devinw1 wrote:
the first think you could try swapping is the LM13700, as it is possible half of it got blown somehow. Do you have an extra 13700 to swap in? Do be careful as those chips are fairly ESD sensitive.


I don't have any extra LM13700's on hand, but lucky for both of us, I bought and built TWO of your modules, so I was able to pop the LM13700 out of my working module and try it out in the non-working one. Sure enough, VCO2 works fine with this IC in place, so I'm chalking up the other IC as "bad" as you suggest. I'll order another one next Mouser order I place and then both these modules should be in business!

Rockin' Banana! Rockin' Banana! Rockin' Banana!

Thanks for the excellent suggestion! I wish I knew enough electronics to understand what to try out for myself, but I'm working on learning what I can towards these ends.
wendallsan
Antistatic mat and wrist strap setup has been ordered to prevent future IC issues as well. Thanks for making me aware of this possibility! Mr. Green
devinw1
Oh good! Yeah, I'll tell you I'm quite careful with electronics and the only things I've ever killed via handling/soldering are JFETs and OTAs. Both are extremely ESD sensitive. The wrist strip and mat is a great idea, and when you handle the OTAs, wrist strap up, then touch the ESD foam in the IC's package, then pick up the chip by the ends (or use ESD safe tweezers). This way you should have no problems! Luckily 13700s are still plentiful and cheap too, so not too much harm done here smile

Glad you got it worked out, and I can guarantee that the more you build and diagnose problems, the more you will learn! SlayerBadger! SlayerBadger!
honeyb
Sweet build! Hope you are loving them. I went for Swedish colors myself.
wendallsan
Very nice indeed, an excellent color scheme!

I'm finding the module to be very flexible with all its features, lots of interesting sounds modulating itself with itself (with itself)! I'm toying with the idea of using it as a primary and secondary oscillator for a complex VCO, with the LFO being extra icing for the project.
honeyb
wendallsan wrote:
I'm finding the module to be very flexible with all its features, lots of interesting sounds modulating itself with itself (with itself)! I'm toying with the idea of using it as a primary and secondary oscillator for a complex VCO, with the LFO being extra icing for the project.


Agreed! Interested to hear some of the ideas you come up with.
wendallsan
My new LM13700 arrived today and the antistatic mat was put to use as it was installed. Module 2 is back online and 2 more of these fine module have been ordered! You only thought this thread was over! I plan to build an entire oscillator bank from these modules and a couple other goodies. Stay tuned for what I hope will be a badass little module with not much of a footprint for what it can do ... probably 4 months of soldering and troubleshooting from now!

(warning: amateur at work)!

screaming goo yo screaming goo yo screaming goo yo

Also stay tuned for some fun oscillator sync examples you can do with your own 2VL1 by itself or with some friends! Also impressive to see Weston Audio hard at work with his new drum module and thru-zero designs!

It's peanut butter jelly time! It's peanut butter jelly time! It's peanut butter jelly time!
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