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TWO59 VCO module (Building Thread) by FEEDBACK
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3, 4, 5, 6  Next [all]
Author TWO59 VCO module (Building Thread) by FEEDBACK
NiteEagle
No need to comment about the your build manuals Andrei. They are one of the best in DIY. That doesn't mean I didn't make a mistake of some kind. The other VCO is probably my fault. More on that later. This one first.

Yes, I purchased all the matching parts from you. 2n5457 etc.

Here's the triangle going into C31.



and coming out.



Here's a shot the resistors that you sent for the 2n5457 for your reference.



Just to explain the double height stand offs are because I socketed the THAT340 with out even thinking. I bought some header extenders so the tempco will clear.
[/img]
strat-1
NiteEagle wrote:
No need to comment about the your build manuals Andrei. They are one of the best in DIY. That doesn't mean I didn't make a mistake of some kind. The other VCO is probably my fault. More on that later. This one first.

Yes, I purchased all the matching parts from you. 2n5457 etc.

[/img]


I know you didn't criticised my manuals, I just made a statement about building many vcos of this project.....this shows the pcbs are not faulty.
They can be faulty from factory, not from design. The producer who I'm working with, have the decency to mark all the defective boards.

The scope picture looks fine, everything in order. It's not clear for me if the voltage refference is correct, before capacitor the signal have to be from 0v to 4v, after the capacitor from approx -2v to 2v.
...So your error is in sine section, look for a short, misplaced value etc.
At the moment I'm in another country at a concert, when I will return I can measure the voltages on a board...if you will not find the error until then.
NiteEagle
Hold off on the voltage checks until I get back to you. Up to you, but I don't want you to waste your time. I have the scope on .1V scale so that triangle is nowhere near where it should be. Let me look at the square wave and check that first part of the oscillator around the THAT340 and then the U4A integrator (right?) and try to see why the voltage level is so low.
groove
What should the frequency range of the VCO be (approximately)? Does it go 20-20k in HF mode? Mine seems to be going from ~50Hz to a few K, I'm wondering if I made a mistake somewhere...

All shapes look good and V/Oct tracking is pretty decent after a pass at calibration.
strat-1
groove wrote:
What should the frequency range of the VCO be (approximately)? Does it go 20-20k in HF mode? Mine seems to be going from ~50Hz to a few K, I'm wondering if I made a mistake somewhere...

All shapes look good and V/Oct tracking is pretty decent after a pass at calibration.


The range is from 27.5HZ - 3000HZ. You should apply cv for high frequencies. So everything is working ok fpr you.
groove
strat-1 wrote:
groove wrote:
What should the frequency range of the VCO be (approximately)? Does it go 20-20k in HF mode? Mine seems to be going from ~50Hz to a few K, I'm wondering if I made a mistake somewhere...

All shapes look good and V/Oct tracking is pretty decent after a pass at calibration.


The range is from 27.5HZ - 3000HZ. You should apply cv for high frequencies. So everything is working ok fpr you.


Great, thanks. Excited to start the second VCO today.
Slomen
On my front pcb´s R45 says 20k, but in the build guide it says 18k. Should I go with the build guide?

EDIT: found my answer in the top post w00t
strat-1
Slomen wrote:
On my front pcb´s R45 says 20k, but in the build guide it says 18k. Should I go with the build guide?


Use the values from the guide. You have the rev1 boards. I updated all the values started with rev1.1 boards. It's the same pcb, so nothing is changed in the sound, I just corrected the printed silkscreen values for the circuit to work at 12v.
If you will look at the schematic you will see I highlighted what parts you need for the circuit to work with 12v and what parts are needed for 15v.
Slomen
Thanks!
strat-1
Slomen wrote:
Thanks!


Cool Armus-skin of evil avatar smile)
Puzzler
I build 2 VCOs and both show similar behavior. Unfortunately I first soldered the 2N5457 wrong so connected was G(pcb)-D D(pcb)-S and S(pcb)-G, inclusive poweruing up. But nothing smoked up or anything.

So all the time its like this:

Switch set to HiFreq gives a very high frequency and the freq pot is not responding at all. As seen in this picture (saw output):



Turning the switch to Lowfreq gives this (saw output):



Freq pot still not responding ofc. Is some IC gone because of the misplaced 2N5457? Or what else did I do wrong?
I checked all the rest but couldnt find any suspicious thing so far.
Any halp would be appreciated!!
strat-1
Puzzler wrote:
I build 2 VCOs and both show similar behavior. Unfortunately I first soldered the 2N5457 wrong so connected was G(pcb)-D D(pcb)-S and S(pcb)-G, inclusive poweruing up. But nothing smoked up or anything.

So all the time its like this:

Switch set to HiFreq gives a very high frequency and the freq pot is not responding at all. As seen in this picture (saw output):



Turning the switch to Lowfreq gives this (saw output):



Freq pot still not responding ofc. Is some IC gone because of the misplaced 2N5457? Or what else did I do wrong?
I checked all the rest but couldnt find any suspicious thing so far.
Any halp would be appreciated!!


The wrongly placed fet will not affect the rest of the circuit, there is a 100u condenser in path of the signal, this condenser will not allow dc voltage to pass to the rest of the circuit.
You say you don't have waveforms at all at the output ?
Puzzler
I do have waveforms, but the frequency is too high on Hi and Low, as seen in the picture.
Switch set to Hi gives a frequency of 5khz minimum.
And ofc the freq, finetune pots are not working.
Sometimes i hear (dont have an oscilloscpope) an unstability in the frequency, it shifts slightlyup and down for a second. Maybe thats connected to the problem.
strat-1
Puzzler wrote:
I do have waveforms, but the frequency is too high on Hi and Low, as seen in the picture.
Switch set to Hi gives a frequency of 5khz minimum.
And ofc the freq, finetune pots are not working.
Sometimes i hear (dont have an oscilloscpope) an unstability in the frequency, it shifts slightlyup and down for a second. Maybe thats connected to the problem.


Please verify if c6 (near u4) is 4,7NF, a smaller value can raise the frequency.
If the value is ok, the mistake is in exponential converter, cv summer section, so you should verify r1-r30. Many wrongly placed resistors from the cv summer (mixer) can raise overall frequency.
Puzzler
Found the problem, VCO is working fine now. Thank you strat-1!
strat-1
3 days work smile



Here is how I solder pn3565 matched transistors. I use thermotube and thermalpaste to keep the transistors in contact.

Swyndger
Hello Strat-1!
You are using 1N5819 in the voltage supply. Not only here, but in almost all your builds (Shaper, Pre-BX, Chorus ...)
Now I have none of them here anymore, but I have a big pack of allmost 100 pc 1N5817.
Can I use them for the VCOs and Shaper, or shall I wait till my order of new 1N5819 arrives?
strat-1
Swyndger wrote:
Hello Strat-1!
You are using 1N5819 in the voltage supply. Not only here, but in almost all your builds (Shaper, Pre-BX, Chorus ...)
Now I have none of them here anymore, but I have a big pack of allmost 100 pc 1N5817.
Can I use them for the VCOs and Shaper, or shall I wait till my order of new 1N5819 arrives?


Yes, without a problem!
jimi23
strat-1 wrote:
3 days work smile



Here is how I solder pn3565 matched transistors. I use thermotube and thermalpaste to keep the transistors in contact.



Will PC CPU thermal paste work in this application? I have some of that left over, I assume its similar stuff. Finishing my VCO's this week, before moving onto the Shaper
strat-1
jimi23 wrote:


Will PC CPU thermal paste work in this application? I have some of that left over, I assume its similar stuff. Finishing my VCO's this week, before moving onto the Shaper


Yes it will work, that's why it's called thermal paste smile
Psy'low
Very well explained manual!
Just noticed it lacks one 2K2 resistor in the BOM.
Will test it this week...
rithma
Is there any quantifiable difference between a 12v and 15v build?
I have both types of supplies, and I heard from several places "you get more bandwidth" from op amps running on +/- 15v, so I am curious why the designer ultimately chose 12v for the guide and BOM.

Which is best?

...btw I've noticed I am tracking my shipment every 15 minutes or so like a madman. Can't wait for this one.

/rithers
strat-1
rithma wrote:
Is there any quantifiable difference between a 12v and 15v build?
I have both types of supplies, and I heard from several places "you get more bandwidth" from op amps running on +/- 15v, so I am curious why the designer ultimately chose 12v for the guide and BOM.

Which is best?

...btw I've noticed I am tracking my shipment every 15 minutes or so like a madman. Can't wait for this one.

/rithers


I chosed 12V, because the kit is designed for eurorack version. I understood also, some builders want to assemble the kit for other formats so I highlighted the 15V values on the schematic.
You can't get more "bandwidth" from the opamps here, there is only 5Vpp signal in the circuit so the 12V power is more than sufficient.
I compared a lot the 12v and 15v version and I heard no difference in the sound.
Think were you want to put the module in your system, it will give you the answer. (what voltage to use)
Slomen
Here is how I solder pn3565 matched transistors. I use thermotube and thermalpaste to keep the transistors in contact.

[/quote]

Am I fine without a thermotube and thermalpaste to keep the matches trans in contact? I have thermal paste, but I dont have that tube. Where can I Get them?
strat-1
Slomen wrote:


Am I fine without a thermotube and thermalpaste to keep the matches trans in contact? I have thermal paste, but I dont have that tube. Where can I Get them?


You don't need thermotube, it was just an example.
Just bent the transistors in a way they will remain in contact and everything will be ok.
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