My VCFive was working perfectly until I fired up the rack the other day and it just died on me. It passes audio on highpass mode, but no resonance, and on BP or LP it passes no audio and does not self-oscillate. Does anyone who is familiar with this circuit know where I should start looking for the ...

When mating the two PCBs, should the power header be on the top (by the potentiometers) or the bottom (by the jacks)? It looks as though the main PCB should be oriented so the power header is on the bottom, but I just wanted to make sure before powering it so I don't fry anything.

Hi mskala, will you consider offering PCB/panel sets?

If these are the CGS114 boards all I can say is good luck. I built one of these a few years ago -- one half worked perfectly, one half still does not work to this day. These specific boards are notorious for being problem-prone... the one I got was bowed in the middle, and I suspect there is a broke...

Yeah, seeing the 18k and the 180k together it is a little more obvious, though I guess my eyesight is going because even under my shoplight its hard to tell... but yeah I should have caught that. Anyway Guest you sussed it out the hard way, can't tell you how helpful that was. Thanks again! :hail: P...

I just measured the rest in that bag and they all measure 18k!! argh I guess a tayda packing error... I kind of got lazy about verifying resistor values, I guess that will teach me. Here's hoping this fixes it!

yeah it's definitely brown grey black orange brown... wtf

it measures 18k pulled completely out of the board... I'm going to put in a 180k and see if that does it... if it does, I'm so sorry you had to troubleshoot my stupidity Guest... remind to get you a nice fruit basket or something...

I measured in situ with the good unit for comparison. Good unit measures 18.5k in situ, bad unit measure 8.8k. (I can still pull one leg up if you want.)

As far as I can tell the board is identical in all respects (component values, polarity, etc.) to the board in the working unit... it's just not behaving the same. It's really got me bummed

wait, resistance, no, I went by color code. I measured the voltages on it with my meter.

R47 is the 180k to -12v... It is the correct value, it reads -12v on one side and -3.21v on the other.

These are the voltage readings I get with my less-than-stellar DMM. Sorry I don't have a scope I know that would be much more helpful. Basically on both the good and bad units, all the marked points fluctuate are the same until you get to the top of the 47k (next to IC5a) and then it's fluctuating b...

At the slowest frequency pin 2 fluctuates between approx. -3.08v and -3.27v. Pin 1 stays flat at 11.08v.

yeah, R49 (R43 below) is correct value (47k) and the saw is present on one side, attenuated on the other. All those resistor values are correct. I went around and re-flowed that area, looked for bridges, etc.-- no dice. :( The 180k that goes to -12v reads -12v on one side and ~ -3.21v on the other. ...

Hi Guest, thanks for the reply. Assuming IC5a is the top right TL072 in the pic of the circuit board I posted-- 1 = 11.08v 2= -3.21v 3= 0.01v 4= -12v 5= 0.63v 6= 0.63v 7= 1.58v 8= 12v On the working unit these are: 1= -5 - 5v (squarewave sig I guess) 2= -.3-3v 3= 0.01v 4= -12v 5= 0.63v 6= 0.63v 7= 1...

Here is the schematic of the original, just for reference. My problem appears to be somewhere in the gray area lower right, since the saw and triangle outputs work fine. https://sneak-thief.com/modular/roland-system100m-vco.png Probing for differences against the XVCO that works, I found the cathode...

Just built an FC XVCO TWO, my second one. Works fine except there is no squarewave output! I have tried swapping the pots and jacks board, and also the ICs, from the working module, so the problem must be a passive component or trace on the main board. The VCO is a sawcore and the saw is fine so the...

Can you be more specific about what was so amazing/different about it? I've never heard one in person, just curious.

Came across this: https://wmdevices.com/products/soft-start-module for $30 it seems like a decent solution. Also looking into DIYing a simple 555 timer based delayed relay to accomplish the same goal. If anybody has any schematics for an equivalent of the above (basically switch power on via relay a...

Side note: I've been having so much fun with the SDSV+ that my rack has remained with only it plugged in... Only problem is now I think I need 4 more of them! Seriously considering building a few more and putting them in their own rack and PSU.

pointless update: I built a simple test rig on stripboard and measured the SDSV+ current draw with my DMM: spec is +/- 30ma and it's sitting at ~ +/- 27ma, so no problems there --- unless this inrush current is too fast for my cheap chinese DMM to read. How long do these spikes last? A few ms? I mea...

After unplugging every module from my rack except the SDSV and BIA in attempt to narrow down the culprit, everything powered up fine with just those two... so I guess it is an inrush current problem.

Hi all, When I power my rack on if the SDSV+ is plugged in the rack seems to receive partial power -- BIA is dead, LEDs are dim on a few modules (NLC 1050 mix/seq), and the SDSV+ itself lights on trigger but gives no audio. This is behavior that I normally associate with a short somewhere in the pow...

Same

EDIT: Whoops, I did get a message and totally missed it during lockdown.