TWO59 VCO module (Building Thread) by FEEDBACK [DISCOUNT!]

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Slomen
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Post by Slomen » Fri Jul 28, 2017 2:56 am

Image Does this look ok? Im using a silicon based "Heatsink".

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Post by strat-1 » Fri Jul 28, 2017 4:27 am

Slomen wrote:Image Does this look ok? Im using a silicon based "Heatsink".
It's not ok. You have to squeeze the transistors together. They should be in perfect contact. Bent the legs in a way they push the transistors to be in contact. The thermal paste should be a very small quanitity, it's role is to cover the scratches, imperfections etc.

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Post by Slomen » Fri Jul 28, 2017 7:22 pm

Thanks strat-1! So I think I fixed it, at least for now of my modules which is now working :party: Buuut, the other one is not. No sound.

There is one fuck up that I dont know is critical: I managed to use a wrong switch on the non-working module. I used a on-off-on switch. Do I need to swap this for the correct one? Or should it work with that switch and something else is wrong?

EDIT: another noob question.. I dont understand the first line of the calibration: "connect a oscilloscoop to pin1 from con2 and adjust sine for a 4.2Vpp amplitude,with vr6 sine ampl adjust." - How do I use my oscilloscope to do this (I have the O´tool)? How do I connect my oscilloscope to pin 1 con 2? Or do I just measure using the sine output?

This by far my most advanced build, I highly appreciate your help :)

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Post by strat-1 » Fri Jul 28, 2017 10:11 pm

Slomen wrote:Thanks strat-1! So I think I fixed it, at least for now of my modules which is now working :party: Buuut, the other one is not. No sound.

There is one fuck up that I dont know is critical: I managed to use a wrong switch on the non-working module. I used a on-off-on switch. Do I need to swap this for the correct one? Or should it work with that switch and something else is wrong?

EDIT: another noob question.. I dont understand the first line of the calibration: "connect a oscilloscoop to pin1 from con2 and adjust sine for a 4.2Vpp amplitude,with vr6 sine ampl adjust." - How do I use my oscilloscope to do this (I have the O´tool)? How do I connect my oscilloscope to pin 1 con 2? Or do I just measure using the sine output?

This by far my most advanced build, I highly appreciate your help :)
It's not necessary to change the switch, but if you want the module to be made by the book, my advice is to destroy the switch with a clamp tool or something. So you will desolder only the legs of the switch, not the entire switch. If you try to desloder the entire switch, you can destroy the board.
Use a desoldering braid to remove the soldering material, after you desolder the legs.
You can use the jack output for sine calibration.

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Post by Swyndger » Mon Aug 14, 2017 4:12 pm

Just to be sure: The both matched 6k8 Resistors in Kit 3 are R72 and R73, in the build manual decribed as 33k. Yes?

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Post by rithma » Mon Aug 14, 2017 5:24 pm

Yes the Sin shape is achieved by testing a variety of resistances, using
temporary trimmers in place of R72 and R73, with the particular JFET you are using. This combo can vary wildly depending on what slice of silicon was used to forge the roll of JFETS on which particular day, and perhaps the phase of the moon at that time.

See page 20 of the build manual "CHOOSING THE SIN TRANSISTOR"

I personally spent the extra money on the kit so that i wouldnt have to dig through jfets and trimmers to shape the sin.

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Re: THAT340 source

Post by Ilpolainen » Sun Aug 20, 2017 2:38 am

batank wrote:I regret not asking earlier, but can anyone recommend a source for THAT340?
(other than Newark/Farnell who charge a wicked $20 freight fee)
Mouser 887-340P14-U

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BOM THAT340

Post by Ilpolainen » Sun Aug 20, 2017 2:41 am

So I just thought to notice that you can add BOM THAT340 Mouser Part.No: 887-340P14-U.

Thanks for AWESOME job. Module not ready yet though. :)

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LED-values

Post by Ilpolainen » Sun Aug 20, 2017 4:13 am

I'm not much of an electrician, so is there any specs I should know about these LED's? I have understood, that they are not all similar, and I can't find any information about them in BOM or build Manual.

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Post by sduck » Sun Aug 20, 2017 12:47 pm

Someone posted part numbers for them - maybe near the front of this thread? I'm not sure. I'll post them here if I find them. I used them, and they work, although they're a bit too bright for my tastes. Not enough for me to dismantle enough to adjust the current resistors though.

Edit: link here - viewtopic.php?p=2504779#2504779
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Post by rithma » Sun Aug 20, 2017 4:51 pm

any specs I should know about these LED's?
I'm not so good at specking out LEDs either, but I took strat's advice and installed little sockets wherever variable parts go. If the LEDs look crappy, just pull out and try some other 5mm parts when you get them.

/E

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Post by rithma » Wed Aug 23, 2017 5:44 pm

Anybody know what the 4V7 diode does in the circuit? Looks to me like it just powers the LEDs; but I'm no engineer.

Will I break anything if I use a different value in its place (maybe a 5V zener?.... its the one part I dont have, and I'M DYING TO HEAR THIS THING!!!!!

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Post by strat-1 » Wed Aug 23, 2017 11:10 pm

rithma wrote:Anybody know what the 4V7 diode does in the circuit? Looks to me like it just powers the LEDs; but I'm no engineer.

Will I break anything if I use a different value in its place (maybe a 5V zener?.... its the one part I dont have, and I'M DYING TO HEAR THIS THING!!!!!
You can use a 5V zener, but no more than this.
It's not powering the led, it's driving the gate for FM modulation located in a CD4066 chip working at 5V.

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Re: LED-values

Post by strat-1 » Thu Aug 24, 2017 3:39 am

Ilpolainen wrote:I'm not much of an electrician, so is there any specs I should know about these LED's? I have understood, that they are not all similar, and I can't find any information about them in BOM or build Manual.
They are absolutely common leds, one opaque 5mm red and one opaque 5mm green.
With the new projects I have to prepare, I completely forgot to update the BOM.

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Post by rithma » Fri Sep 01, 2017 1:54 pm

I just finished building my VCOs, and I love them love them love them. Best documentation in DIY!!!

One VCO is working as expected( :banana: :yay: )
However one has
-no square wave output
-and this from the sin output:
Image

I haven't had much time to poke around yet, but maybe somebody has an idea of where to start looking?

In the meantime, I'm off to build the shaper. 8-)

/E

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Post by strat-1 » Fri Sep 01, 2017 10:29 pm

rithma wrote:I just finished building my VCOs, and I love them love them love them. Best documentation in DIY!!!

One VCO is working as expected( :banana: :yay: )
However one has
-no square wave output
-and this from the sin output:
Image

I haven't had much time to poke around yet, but maybe somebody has an idea of where to start looking?

In the meantime, I'm off to build the shaper. 8-)

/E

My advice is to use the good vco as a test target. Look at the schematics and read with the scope voltages in various points, repeat the readings on the bad module.
If something is different in a point, look there for a bad solder joint, short, wrong part, defective part etc.

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Post by rithma » Sat Sep 02, 2017 8:57 pm

Got It!!!
After building the troubleshioting wiring harness, and an hour of poking around, i found 1 bad joint (missing square wave) and one backwards JFET(bad sine wave). All works now! Chubby sine waves all around.

Thank sweet baby jeesus for sockets.

/Etienne

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Post by StudentsOfTheFuture » Wed Oct 04, 2017 11:24 pm

Bumped the other thread by mistake :oops:

First - thank you strat-1, this has been an awesome project!

Just finished my VCOs (from kits), one works 100% and one half works.

The half working one has an issue with the main board (because I can swap front boards and get the same thing) - the pitch fluctuates randomly and the waveforms sound distorted.

Any idea what might be to blame? I messed up installing the low freq linearity trimmer and ripped a trace replacing it, but the connections seem to test okay. And that seems like it would be unrelated...

Waveforms, FM, Frequency, Fine, and Lock all seem to work fine, other than the above. I haven't tested more extensively yet.

e: and to eliminate the obvious, components are where they should be, and caps/diodes/ICs are the direction they're supposed to be.

Per schematic it looks like something upstream of the individual waves, so I re-heated some joints around the transistor pair and IC.

I get good tracking for about a minute after leaving it off for a while. I thought I had fixed it and was just tuning it against the other one to make sure when the weirdness came back. That makes me think capacitors?
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Post by StudentsOfTheFuture » Fri Oct 06, 2017 2:25 am

Huh, now it seems to be working...

I reflowed some joints based on the schematic and my best guesses and no luck... then went to the movies, came back, plugged them in to do some voltage metering and... that seemed to do it somehow?

Checked the THAT340s and the transistors (basically... the hard stuff to replace) and the readings matched on both, and figured I should do a test run just in case. I was able to tune them within a note of each other without calibration, and I have them out of phase droning now just to make sure it holds - I'm getting normal osc drift, not random jumps! (and gosh they sound beautiful).

All of this has me thinking theres a bad joint somewhere. I'm wondering - any obvious culprits for the pitch fluctuations? I figured it was tempco, THAT, or PN3565s, but they all seem okay (actually, I should check the Tempco). And beyond that I'm not sure where to look (but feel free to direct me to schematic sections or general clusters - I do want to learn!)
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Post by sduck » Fri Oct 06, 2017 10:57 am

Clean the flux off?
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Post by StudentsOfTheFuture » Fri Oct 06, 2017 2:08 pm

That's usually my first step (pre-power, even). I guess if it ain't broke... On to calibration!

e: okay, I think i'm getting closer: I can get the weirdness for about a minute or two after powering on (30 seconds normal, then 2 minutes of jumpiness, then it goes away). Seems consistent with the other oscillator evening out its tuning as it warms, just way more pronounced til it gets there.

This is making me think its just due to a sloppy application of heatsink gel on the tempco.

Anyway, a very workable problem to have (I was thinking if all else fails, well, I know which one the mod osc is gonna be).
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Post by Jarno » Sun Oct 08, 2017 10:32 am

Finished the build of the two VCO sections today. But only one of them is working, unfortunately.
I've built them at the same time,so I stuffed components in both boards per value. The only differences are that I used solder straps instead of diodes in the non-working board (and diodes in the other), and that the non-working board has a 2N4339 and the working board has 2N5457, the paired resistors had the same value markings, but everything was packed together, so I couldn't distinguish if one pair of resistors went with the one FET and the other with the other FET, but his should only affect the sine output.
On the non-working board,none of the outputs work, I've isolated the problem to the main board, both control boards are OK. I haven't connected pin 9-10 as discussed in the errata section, but that shouldn't matter, right?
As it doesn't oscillate, I am suspecting U4 to be bad, does that make sense? If I check both sides of the 4n7 cap, I only see DC on the scope and no oscillation.

This is the one that does work :D :
Image
Image
Image

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Post by sduck » Sun Oct 08, 2017 1:13 pm

Why did you skip the diodes? I'd guess that's at least part of the problem. Put the diodes in there.
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Post by Jarno » Sun Oct 08, 2017 1:32 pm

Those are the diodes in the power supply section, and are meant to prevent reverse polarisation of the connector. This is not likely to happen (boxed header), therefore I replaced them by wires. Why do you think this is part of the problem?

Edit:
Mine is running on eurorack-standard voltages, so +/-12v (rather than +/-15v).

Edit2:
By the way, the picture above is of the functioning VCO, the one that does not function does have the polarity protection diodes.

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Post by StudentsOfTheFuture » Sun Oct 08, 2017 6:35 pm

The resistors I got seemed interchangable - they tested the same on my (limited, but usually good for finding 1% tolerances) meter.

I had the same semiconductor for both sine shapers, though - looked like the same batch.

How do the U4 pin voltages compare between the two? That would rule that out, at least.
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