MST VC LFO - DIY

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JohnLRice

MST VC LFO - DIY

Post by JohnLRice » Sat Apr 04, 2015 9:39 am

Finished the MST VC LFO this morning. :party: Here's some quick pictures:

Image

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lpgeffen
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this was one of my first Synthrotek builds

Post by lpgeffen » Mon May 04, 2015 5:09 pm

I got the pcb and panel from Synthrotek, sourced the rest from Mouser and built it in a few hours. Worked the first time and I use it all the time.
8-)

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ilya.n
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Post by ilya.n » Sat Aug 08, 2015 8:32 pm

I was wondering if I could use a 1M pot instead of 500K (happened to have handy the former not the latter).

Thanks.

wickedCircuits
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Post by wickedCircuits » Mon Aug 10, 2015 2:14 pm

ilya.n wrote:I was wondering if I could use a 1M pot instead of 500K (happened to have handy the former not the latter).

Thanks.
While you probably could use a 1M pot, it may alter the waveforms that the LFO produces significantly. I'd be interested in seeing the results :)

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Post by mmm » Tue Sep 08, 2015 10:52 am

ilya.n wrote:I was wondering if I could use a 1M pot instead of 500K (happened to have handy the former not the latter).

Thanks.
You have my blessing 8-)

1M will be fine

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ilya.n
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Post by ilya.n » Tue Sep 15, 2015 3:59 am

mmm wrote:
ilya.n wrote:I was wondering if I could use a 1M pot instead of 500K (happened to have handy the former not the latter).

Thanks.
You have my blessing 8-)

1M will be fine
Thanks George!

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ilya.n
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Post by ilya.n » Tue Sep 15, 2015 4:47 am

BTW i am getting the range of 40s to 130HZ, is this normal?

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Post by mmm » Tue Sep 15, 2015 2:12 pm

ilya.n wrote:BTW i am getting the range of 40s to 130HZ, is this normal?
Here's the specs I submitted:

Specifications:

Voltage controlled LFO with Sine, Triangle and Square wave outputs.
Skew control for altering Waveform symmetry.
Iv+ = 11.75 mA
Iv- = 12.2 mA

Manual range: Approx 51 Second to Approx 102 Hz.

Time with Max range, +5V CV: 1,450 Hz
Time with Max range, -5V CV: 1 Hz

Time with Min range, +5V CV: 2 Hz
Time with Min range, -5V CV: Stalls. I think. Not much change after 3 hours.
-4.5V CV: 1.33 hours/ cycle. Pos 80%, Neg 20% with centered sym.
-4.75V CV:

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wily
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Diode

Post by wily » Thu Dec 31, 2015 12:31 am

I built one of these six months ago from the Synthotek kit and it's a great little LFO. Very useful for OSC FM.

Recently it stopped working (wouldn't oscillate), and I pulled out the multimeter and noticed one of the diodes (D5 IIRC) is no longer functioning. Any ideas why this could occur?

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Re: Diode

Post by mmm » Thu Dec 31, 2015 12:59 am

wily wrote:I built one of these six months ago from the Synthotek kit and it's a great little LFO. Very useful for OSC FM.

Recently it stopped working (wouldn't oscillate), and I pulled out the multimeter and noticed one of the diodes (D5 IIRC) is no longer functioning. Any ideas why this could occur?
Bad diode? it happens. call Synthrotek.

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Re: Diode

Post by mmm » Thu Dec 31, 2015 1:38 pm

wily wrote:I built one of these six months ago from the Synthotek kit and it's a great little LFO. Very useful for OSC FM.

Recently it stopped working (wouldn't oscillate), and I pulled out the multimeter and noticed one of the diodes (D5 IIRC) is no longer functioning. Any ideas why this could occur?
Actually, D5 is one of the reverse voltage protection diodes. It's a 1N914.
You can replace it with that or a 1N4148 or any small signal diode with a reverse PIV of 30V or more.

The board probably isn't getting balanced power. thus, it protests. :confused:

They cost like $0.02.

If that is what failed, that will get you up and running quickly.

GM

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Re: Diode

Post by synthetek » Thu Dec 31, 2015 3:16 pm

mmm wrote:
Actually, D5 is one of the reverse voltage protection diodes. It's a 1N914.
You can replace it with that or a 1N4148 or any small signal diode with a reverse PIV of 30V or more.
Same thing happened to mine , I plugged in another module with a bad power cable and then my MST LFO stopped working. I found out that it was D5 and replaced it and everything was fine.

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Re: Diode

Post by mmm » Thu Dec 31, 2015 5:54 pm

synthetek wrote:
mmm wrote:
Actually, D5 is one of the reverse voltage protection diodes. It's a 1N914.
You can replace it with that or a 1N4148 or any small signal diode with a reverse PIV of 30V or more.
Same thing happened to mine , I plugged in another module with a bad power cable and then my MST LFO stopped working. I found out that it was D5 and replaced it and everything was fine.
Glad it doubled as a fuse :guinness:

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wily
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Post by wily » Mon Feb 08, 2016 12:29 am

Oops, forgot to watch this thread, I'm bad at foruming.

Just to let you know, I replaced the diode a few weeks ago and it's working great again. Pretty sure I didn't do anything dodgy with PSUs but you never know.

These are really great little LFOs. I should build another one.

Edit: PS, thanks mmm! :hihi: :guinness:
wily

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Post by mmm » Mon Feb 08, 2016 12:52 am

wily wrote:Oops, forgot to watch this thread, I'm bad at foruming.

Just to let you know, I replaced the diode a few weeks ago and it's working great again. Pretty sure I didn't do anything dodgy with PSUs but you never know.

These are really great little LFOs. I should build another one.

Edit: PS, thanks mmm! :hihi: :guinness:
:bananaguitar:

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colossus
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Post by colossus » Wed Feb 24, 2016 8:50 pm

Built one of these up last week. If any newbies are wondering, it was a really, really simple build. Highly recommended as a first or second build. And it sounds great!

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strangegravity
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Post by strangegravity » Wed Apr 06, 2016 1:36 pm

Likely the most used LFO in my rack. CV response is great, 4 HP three simultaneous waveforms. Cant beat it!

Great looking build OP!

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stringsthings
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Post by stringsthings » Tue Jun 28, 2016 5:15 pm

Finally got around to building this. Fired right up. Very pleased with this module.

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Post by dubtoms » Mon Aug 22, 2016 9:58 am

Hello, I finished building one of these today but it does not seem to oscillate. The red led is always shining when powered and it looks like I’m not getting anything from the outputs…
What do i need to check ? What voltages should I get at control pins ?

Thanks in advance,

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dubtoms
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Post by dubtoms » Thu Aug 25, 2016 12:10 am

BUMP :hmm:

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Post by dubtoms » Wed May 03, 2017 8:00 am

That was a lot time ago but I pretty much learned that you need to check pinouts for transistors before substituting them... :hihi:
I ended up figuring that by myself but I had a lot of support from Mr. Mattson himself, who is very responsive if you contact him via email.

Anyway, it's a great little module, like pretty much everything in the MST line ! :yay:

JohnLRice

Post by JohnLRice » Wed May 03, 2017 8:31 am

dubtoms wrote:That was a lot time ago but I pretty much learned that you need to check pinouts for transistors before substituting them... :hihi:
I ended up figuring that by myself but I had a lot of support from Mr. Mattson himself, who is very responsive if you contact him via email.

Anyway, it's a great little module, like pretty much everything in the MST line ! :yay:
:tu: :party:

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Post by mmm » Wed May 03, 2017 10:21 am

dubtoms wrote:That was a lot time ago but I pretty much learned that you need to check pinouts for transistors before substituting them... :hihi:
I ended up figuring that by myself but I had a lot of support from Mr. Mattson himself, who is very responsive if you contact him via email.

Anyway, it's a great little module, like pretty much everything in the MST line ! :yay:
I actually ran into that when I designed my VCO. The "stock" pinout for the FETs on the CAD schematic program were a different pinout than the specific FET I was using. I didn't even think about it before ordering the prototype boards. It was "real fun" troubleshooting that...

:mmm:

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