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unstable vco + power problems
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author unstable vco + power problems
atmosplak
Hello everyone!

Long-time lurker here with a question or two. FYI i've done quite a bit of research prior to breaking down and starting a new thread so hopefully i'm not beating a dead horse here.

I recently purchased a powered case (12u/104hp) housing two Meanwell RT65b PSUs with the following specs:

+12v 2800ma - max 3500ma
-12v 500ma - max 1000ma
+5v 8000ma

With my current rig, i'm approaching the -12v limits (pulling around 1.4amps currently) placing me at about 75% total MAX output. I've got quite a bit of +12v headroom still and I have no modules requiring +5v.

I plan on buying a 5v dummy load soon, but something tells me my issue is a result of something else.

Now for the issue. My Furthrrrr's been acting pretty funky lately - obvious instability, excessive drifting (it's analog, but gimme a break), and this interesting phenomenon where the blinking lights from its neighbor's lfo causes the FG to modulate. Can anyone shine a light on this?

I should have done more research prior to buying the case, I know, but it's the perfect size for my setup and i'm really happy with the build. I'm just unsatisfied with its power. Has anyone ever ripped the PSUs out of their off-the-shelf racks and installed more robust ones?


very frustrating Dead Banana
abelovesfun
I've never used your power or your oscillator, but noticed in my own case that LFOs would cause slight modulation in some of my MFOS analog VCOs.
I ended up separating the power and in my live rack, I now use four smaller power supplies (they are AI synthesis supplies, but anything will do).
I have one for oscillators
I have one for a row of MU
I have one each for two rows of Euro with high draw modules.

All of those sit inside the back of my case which has 2 rows of 5u and 2 rows of Euro in a 16 space shallow 19" rack.
arthurdent
atmosplak wrote:
Now for the issue. My Furthrrrr's been acting pretty funky lately - obvious instability, excessive drifting (it's analog, but gimme a break), and this interesting phenomenon where the blinking lights from its neighbor's lfo causes the FG to modulate. Can anyone shine a light on this?

If the LFO is right next to the Furthrrrr, maybe try moving it farther away, see if that makes a difference. It could be a proximity issue rather than one related to feedback through the power bus.
cornutt
Are the two power supplies operating separately, or do you have them strapped together? If they are separate, how is the -12V draw divided between them?
Rex Coil 7
... here we go again ....
atmosplak
arthurdent wrote:
atmosplak wrote:
Now for the issue. My Furthrrrr's been acting pretty funky lately - obvious instability, excessive drifting (it's analog, but gimme a break), and this interesting phenomenon where the blinking lights from its neighbor's lfo causes the FG to modulate. Can anyone shine a light on this?

If the LFO is right next to the Furthrrrr, maybe try moving it farther away, see if that makes a difference. It could be a proximity issue rather than one related to feedback through the power bus.


Yep, this is the route i ended up taking. I moved my FG to my Doepfer case (which I originally bought to house an all tube mini-rack). This'll have to do until I can address the issue with a more permanent solution.

Thx for the suggestion
atmosplak
cornutt wrote:
Are the two power supplies operating separately, or do you have them strapped together? If they are separate, how is the -12V draw divided between them?


I bought the case with power installed. AFAIK the two supplies are daisy chained as I only have a single power inlet. Not sure how the -12v draw is divided between them.

Assuming daisy chaining implies that they're connected in series, i'm inclined to think that they share the load, so to speak. I'm probably wrong in this assumption though.
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