[Order] Roland 100M VCO PCBs/panels aka System X Oscillator

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MikkoM
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Post by MikkoM » Thu Aug 11, 2016 10:07 am

What is the function of 5.6nf cap in this circuit and can it be replaced with some other value ? I have little trouble to find that value.

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fitzgreyve
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Post by fitzgreyve » Fri Aug 12, 2016 2:47 am

MikkoM wrote:What is the function of 5.6nf cap in this circuit and can it be replaced with some other value ? I have little trouble to find that value.
It's a filter on the CV input - you can probably change it to 4n7 or 6n8 with minor effect on the ciruit.

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Post by shiftr » Sun Jan 22, 2017 6:19 am

I've build this a while ago but i can't get it stable enough to be really usefull.
I think it's mostly the temperature shift when i calibrate it out of the case and then it gets a lot hotter inside the case.
I've seen people use a special heater circuit in this thread. Is that a PCB that is available from somewhere?

[EDIT] :doh:
Just look at the frequency central website first before posting.
It's there : http://www.frequencycentral.co.uk/?page_id=249

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mbroers
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Post by mbroers » Tue Jan 24, 2017 10:07 pm

Ive heard there is a mod to change the pitch knob to a rotary switch for octave but I can't find documentation anywhere.. has this been covered in a different thread or forum?

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sicpaul
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Post by sicpaul » Wed Jan 25, 2017 6:33 am

thread of octave switch: viewtopic.php?t=118055
I love mine :love: - not to forget i love the whole Sys-X VCO(s)
thanks to Mark and Rick :yay:
Maybe of interest too: 100m/Sys-X VCO driver (including Octave switch)

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mbroers
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Post by mbroers » Wed Jan 25, 2017 11:44 am

thanks!

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DJMaytag
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Post by DJMaytag » Thu Feb 09, 2017 11:48 am

Grumskiz wrote:I'd say use polystyrene or another high quality type for the 2n2 capacitor that is next to the JFET. This is the cap that gets charged to produce the sawtooth wave, all other waves are derived from it. The other caps are less critical, I think, so use whatever you have.
Rick seems to use mostly Tayda parts, at least in his BOM PDF's with links, so the 2n2/5n6 would probably be similar to these, if not these exact parts:

2n2 at Tayda and 5n6 at Tayda

Earlier in this thread someone had a Mouser cart with WIMA's in it, but someone noted they wouldn't fit. It looks like there are some new parts at Mouser that are thinner that some other WIMA caps in these sizes. The Tayda box-poly caps are 7.5mm long x 2.5mm wide (I don't think the height matters). It looks like these WIMA's will fit that footprint:

WIMA FKS2D012201A00JSSD

Should these work out OK?
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fitzgreyve
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Post by fitzgreyve » Wed Feb 15, 2017 4:17 pm

sicpaul wrote:thread of octave switch: viewtopic.php?t=118055
I love mine :love: - not to forget i love the whole Sys-X VCO(s)
thanks to Mark and Rick :yay:
Maybe of interest too: 100m/Sys-X VCO driver (including Octave switch)
I'm currently out of octave switch PCBs - if there is renewed interest I can get a batch ordered.

I still have a small stock of VCO driver PCBs and panels.

PM if interested in either.

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williamcarthief
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Post by williamcarthief » Wed Feb 15, 2017 7:18 pm

I PM'd but just want to tell the whole world of my desire for three octave switch pcbs.

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OB1
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Post by OB1 » Thu Feb 22, 2018 2:44 am

Has anyone done a Mouser project for this build? I saw one in this thread, but the link seems to be dead.

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OB1
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Post by OB1 » Fri Mar 09, 2018 3:46 am

Just finished one of these - it's a great VCO! Gonna build another one straight away!

Image

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truman_k
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Post by truman_k » Sun Mar 18, 2018 12:54 am

did anyone has problem in adjusting the duty trimmer to get a full range of pulse width? i can only achieve a certain range from 50% to 16%. I can only shift it up or down never been able to get the full range of 100-0% or even 50-0%?

is there anything mod need to be done to achieve this?

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fitzgreyve
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Post by fitzgreyve » Mon Mar 19, 2018 4:38 am

Looking at the FC VCO schematic, R44 (220k) (connected to the manual pulse width pot) should control the manual PW range - reducing the value of this resistor will increase the manual PW range.

I'm interested how you get on with this ?
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truman_k
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Post by truman_k » Tue Mar 20, 2018 3:12 am

fitzgreyve wrote:Looking at the FC VCO schematic, R44 (220k) (connected to the manual pulse width pot) should control the manual PW range - reducing the value of this resistor will increase the manual PW range.

I'm interested how you get on with this ?
Thanks for your suggesstion, i may give it a try, and let you know the result

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truman_k
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Post by truman_k » Tue Mar 20, 2018 11:11 am

After changing the 220K (R44) to 150K, I got the range of duty cycle from 50% to 1%, which is good enough. (I have tried 100K, which reduced too much, maybe a 120K is a good choice but I don't have that on hand) :nana:

Thanks fitzgreyve

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Gamma Phonic
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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by Gamma Phonic » Fri Mar 13, 2020 10:04 am

Hi, I’m new here and new to modular in general.
Years ago, I bought this panel and pcb but never got round to building it until just now. I’ve soldered everything in and it all looks good but when I plug in power to test it I get absolutely nothing. From all three of the waveform outs, not a peep. I’ve reflowed all of the solder points, twice. I’ve checked them all with my multi meter. They’re all good. But still nothing. I’m not new to soldering, but I’m far from an expert in electronics and I was wondering if anyone had any advice for troubleshooting? My only thought is that the ICs might be bad? But I have spares which I have tried with no luck. Any thoughts on how to proceed would be welcome.

Thanks

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woodster
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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by woodster » Fri Mar 13, 2020 11:53 am

If you're confident in your soldering, and all IC's are installed correctly in the right places then maybe check if you've wired up the Jack's wrong?

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fitzgreyve
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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by fitzgreyve » Fri Mar 13, 2020 1:53 pm

Gamma Phonic wrote:
Fri Mar 13, 2020 10:04 am
Any thoughts on how to proceed would be welcome.
Post decent pictures (PCB top, bottom, wiring) and we'll see if anyone can spot anything (if this has the plug-in "heater" PCB, probably best to remove it and photo separately).
Under developement:
- "Muse"
---------------------------------------
https://fitzgreyve2.blogspot.com/

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tobb
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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by tobb » Fri Mar 13, 2020 6:57 pm

For fun have drawn couple years ago this vco in 4U format,added the heather and octave switch range,also did the VCF/VCA,etc. never tested so far.
100M vco.jpg
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Gamma Phonic
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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by Gamma Phonic » Sat Mar 14, 2020 5:06 am

fitzgreyve wrote:
Fri Mar 13, 2020 1:53 pm
Gamma Phonic wrote:
Fri Mar 13, 2020 10:04 am
Any thoughts on how to proceed would be welcome.
Post decent pictures (PCB top, bottom, wiring) and we'll see if anyone can spot anything (if this has the plug-in "heater" PCB, probably best to remove it and photo separately).
I’ve just noticed the socket for the CA3046 is a bit wonky. I’ve checked the connections for continuity and they seem fine, I’ll take it out and redo it anyway.

Thanks in advance for pointing out were I have gone wrong lol.
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Gamma Phonic
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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by Gamma Phonic » Sat Mar 14, 2020 5:35 am

woodster wrote:
Fri Mar 13, 2020 11:53 am
If you're confident in your soldering, and all IC's are installed correctly in the right places then maybe check if you've wired up the Jack's wrong?
Thanks for the tip. I’ve checked it and it all seems to be in order.

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fitzgreyve
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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by fitzgreyve » Sat Mar 14, 2020 10:57 am

Can't see anything obvious from the pics (haven't gone as far as checking values!).

the lack of any output at all suggests that the sawtooth core (first page of schematic) isn't oscillating, I would get this working first and worry about triangle and pulse after.

I'm assuming resistor values etc. have already been checked - again I'd just look at the core to start with.

Refering to attached schematic:
0. check +12v and -12v present at all relevant IC pins.
1. check that voltage at pin 1 of IC1 (tl072) changes when "range" control is moved - you should get approx 3v swing at pin 1over the whole range (proves CV input summing is working)
2. all the transistors look to be correctly oriented, but check TR1,TR3 are PNP, TR6 is NPN. Also, if not using BC547/BC557 the pinout may be reversed.
3. If not using 2N5485 for the FET, again check for reversed pinout.
4. IF TR6 is defunct, it could be holding the core in "reset" (more likely if switched to "strong" sync) - setting to weak sync AND removing R22 temporarily could rule that out until it oscillates.
5. Where did you source your CA3046 ?

I've built four of these with no significant issues.
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Under developement:
- "Muse"
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https://fitzgreyve2.blogspot.com/

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Gamma Phonic
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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by Gamma Phonic » Sat Mar 14, 2020 4:27 pm

fitzgreyve wrote:
Sat Mar 14, 2020 10:57 am
Can't see anything obvious from the pics (haven't gone as far as checking values!).

the lack of any output at all suggests that the sawtooth core (first page of schematic) isn't oscillating, I would get this working first and worry about triangle and pulse after.

I'm assuming resistor values etc. have already been checked - again I'd just look at the core to start with.
I followed your advice. I think it might be the CA3046, I read only very small voltages on the pins (<0.1V). Which is odd. Even if it was a dud, I would expect to read something on at least some of the pins? As I said, I’m no electronics expert. I bought two of them from an eBay seller, same results on both.

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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by dougt » Sat Mar 14, 2020 9:17 pm

CA3046 with a 2018 date code seems fake to me. Did you get it from China?

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Gamma Phonic
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Re: [Order] Roland 100M VCO PCBs/panels aka System X Oscillator

Post by Gamma Phonic » Sun Mar 15, 2020 2:38 am

dougt wrote:
Sat Mar 14, 2020 9:17 pm
CA3046 with a 2018 date code seems fake to me. Did you get it from China?
It was a London based seller. But I think it’s a dud. Can you, or anyone else, recommend somewhere to buy a good one? In the meantime, I’ll go double check the resistor values.

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