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Roland System 700 DIY VCO
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2, 3  Next [all]
Author Roland System 700 DIY VCO
roginator
I was after best design of uA 726 to add that VCO to my system ...

so I decide it will be System 700 oscillator with all features!!!

im new to PCB design but so far im good with it ( at least I think i am)

Idea is to put 700 VCO into MU format 2 space modules .. and that is not mission impossible!

here is how new PCB will look ...100% original clone!



and this was original ..



I did some calculations and all parts for 700 VCO will be around 150 euro including panel and knobs ( I can offer plain PCBS if somebody will be interested) it will be awesome sounding VCO and simple DIY project!
jcoplin
Interesting, but where can you get ua726 that aren't fakes? Do you have a proposed panel layout?

James R. Coplin
roginator
jcoplin wrote:
Interesting, but where can you get ua726 that aren't fakes? Do you have a proposed panel layout?

James R. Coplin


I have some 726 for my needs for start .. panel layout soon!

I will offer PCBS !
roginator
this is just idea how panel layout will look!

ringroad1
heh, I've been looking closely at the System 100 oscillator recently. I'm similarly keen on making an accurate clone.

I've got some ua726 on a speculative order from China, but like James says, there's a likelihood that they are fakes. Also there's the concern of building new stuff with (very) obsolete parts. Have you been able to test your ua726? (and how?)

The Curetronic clone of the System 100m (not System 100) VCO uses a CA3046 instead of the ua726, presumably using one of the transistors inside as a heater. I'm wondering about going down this route and keeping the 726 for spares if I can work out how it's done.
roginator
I have many gear with 726 so to test it is no problem smile!!

so far i have enough to make some nice 702 VCOs !!

and PCB design is done .. here are some pictures !!


(attachment deleted) - luka


here is scan of original VCO PCB



SCHEMA

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

PCBS arrived ...


(images deleted) - luka
roginator
Half done ... now shopping for rest of small parts smile


(attachment deleted) - luka
steffensen
Whats the size of these boards? Im thinking eurorack ofc. grin
Good work! thumbs up
BugBrand
Curious about the special of this design?

uA726, yes, should provide decent temperature stability - but there'd be more standard (ie. NOT using the rare-as-anything uA726) ways around this.

Beyond that, it appears not too dissimilar to quite standard saw-core VCO approaches + not irregular waveshaping.

Not meaning to rain on your parade! Just curious..
Nice blue PCBs though!
astroschnautzer
Interested if they fit euro, bought a working ua726 from polida2008 at ebay a few months ago.....
lysander
BugBrand wrote:
Curious about the special of this design?

uA726, yes, should provide decent temperature stability - but there'd be more standard (ie. NOT using the rare-as-anything uA726) ways around this.

Beyond that, it appears not too dissimilar to quite standard saw-core VCO approaches + not irregular waveshaping.

Not meaning to rain on your parade! Just curious..
Nice blue PCBs though!

I'm interested in this too for the sake of curiosity.
Very nice work on the PCBs though!
filterstein
Great, I'd like pcb's for two vco's.
But i'd like it better if you could supply the 726's too.
Be carefull with testing them in good equipment, i got fakes that would have shorted the circuit out.
roginator
Hi Guys

- PCB size is 126mm x 135mm ..and its copy of original one !
- It fit 5U format perfect smile)))

I have 1 left BUT can run another limited run of 20 pcs
https://www.muffwiggler.com/forum/viewtopic.php?t=78319&highlight=702

- I have enough 726 ( original ones for my needs so .. ) smile


.....

here is picture of Panels that are in production for this baby VCOs smile
if System 700 VCOs were good mr.Moroder they are good for me we're not worthy .. I love sound of vcos based around 726 smile))))

ashleym
Having never studied the front panel of one of these, I had never noticed the switch above the modulation input for dividing it by 10. Now that is a good idea thumbs up
sonicwarrior
What is 'Pitch' vs. 'Semitone'?
matia
those original vco's look identical to what's inside my SH7 ;-) they will sound huge!!!!
roginator
There is small error on PCB !!

so far only 1 error I found ( heh might be more .. but one is ok oops )
roginator
PCB should be corrected like this (correction made on PCB file)
janvanvolt
4 Parts missing and then first audio tests :-)

For reference/stuffing:

Q1 - NF510
Q2 - 2SC945
Q3 - 2SA733P
Q4 - 2SA733P
Q5 - 2SC945
Q6 - 2SC945
Q7 - 2SC945
Q8 - 2SK30A-GR
janvanvolt
LM311 and 15pf missing, then i'm finished and ready for first sounds.
EML
Hi Roginator,
I've sent you a PM.
Eric G
I found really nice System 700 pix:

Arkdigital: http://www.arkdigital.net/Pages/RolandSystem700.html
janvanvolt
Okay, my VCO's are finished.

Can anybody check what the minimum level of pots/switches i need to use to verify operation ? it definitely needs the range switch (but still no signals)
janvanvolt
VCO done.
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