Minimoog, Oscillator 1 & 2 Propblem

[1000keys]

Hi all,

I`m new to this forum.

I`ve a Minimoog for a longer time now and observed in the last time a significant difference in sound only with the square waves of oscillator 1 and 2.
The square of the 3. sounds completely clean and strongly hollow (like it should be) and like those of my other synths. But 1 and 2 more like a sawtooth wave and slightly velvetly, but despite hollow but far less than the 3.

Has anybody an idea where I have to spot this in the electronics.
I know, the Instrument is pretty old and rarely used, absolutely no scratching of any other pot, all is working fine, even the wave selectors.
All other waveshapes sound also completely the same.
I`ve been already told, if the +/- 10 Volt of the powersupply wouldn`t be there correctly ALL 3 oscillators wouldn`t work.
Also, there are no caps in that circuit area, only resistors, but other caps would eventually ! cause all this, I`ve been told.

Have I to focus other parts inside ?

[thealien666]

Hi and welcome.

Anyone familiar with the venerable Minimoog D knows that this is the usual behavior for this classic synth, with all its other classic quirks like: the envelopes short peaks higher then the set sustain level, the saturated filter when mixer levels are set to more than 7, the mod wheel modulation faint bleeding even with the mod wheel at minimum, the different glide speeds for a given time setting depending if it goes up, or down, the slight and slow pitch drift of the oscillators over time, the different pitch bend range of the pitch bend wheel depending on up or down, etc etc...

All part of the Minimoog D charm, and all perfectly normal.

A perfect, precise, digital machine this certainly isn't. And we can thank Bill Hemsath, Jim Scott, Chad Hunt, and of course Bob Moog (the creative team behind the Minimoog D) for that !

So, stop worrying about it and simply play something on it !!

[1000keys]

As nobody else gave a respond it seems true that you hit the point.

But still it`s very odd to me that a Minimoog has oscillators with Imperfect square waves.
There MUST be somehow anything be done to adjust.
It`s really disappointing to have mostly saw instead of square waves.
I won`t let lose before I`ll find a way to improve.

But about the rest, the saturation of the Filter I know about, and the Envelope behaviour.
But the rest you mentioned I don`t have on mine.

Thank you despite.

[GregAE]

Check out the first couple of minutes of this video and you'll see that the the Mini's square wave is far from an ideal square:

https://www.youtube.com/watch?v=jvA4hdHpJfA

- Greg

[EricK]

That's my video, I just got the Mini over the summer and had it serviced at that time. Here are some shots of the waves to save you a few minutes.

[1000keys]

Oh, how impressive what images sometimes can tell.
I`d wish I could have a machine like that but I cannot afford. They seem to be pretty expensive.
Curious about, if my Mini would show the same or similar.

[EricK]

I only paid about 300 for that oscilloscope, and you can find them much cheaper than that on places like ebay.


http://www.ebay.com/usr/workingman.mv?_ ... 2749.l2754
I purchased mine from this seller, and it was packed well and had been serviced. I think he is in Missouri. He currently doesn't have anything for sale but a good friend of mine and tech pointed the unit out to me. You can find all types of used and off-brand scopes as low as 20 bucks, with no guarantees of course.

Eric

[chekmate99]

hi there,

is it possible for someone to briefly explain the connections between the synth and your oscilliscope - do you require a CV Output and ground from your synth or are the connections being made with the cover of the synth being opened?

thanks,

Chris.

[EricK]

To monitor the waveform I simply used a small patch cord connected to the mini's audio output and touched the probe to the tip of that plug.

[RL]

Hi Eric,
it seems your scope is AC coupled. You better connect it DC coupled.
Have fun,
Rudi

[EricK]

Rudy,
Done. Was I about to damage something?

[RL]

Was I about to damage something?

No, of course not.
The wave forms look better when it is DC-coupled.
Have fun,
Rudi

[chekmate99]

Thanks Eric - works fine with my oscilloscope.

Chris.

[EricK]

Rudi,
Thanks for the tip. I bought that scope and had/have absolutely no idea how to use it so I tweaked knobs until I got a reading. I use it for eye candy. I have no EE skills, and no Elmer but love watching the waveforms nonetheless.

Checkmate,
No problem. You still might want to read the manual because prior to Rudi's post I had no idea that more information would be imparted to the wave depending on the settings. I'm not taking any measurements though and that scope is way more powerful than anything I would ever use it for.

[1000keys]

I only paid about 300 for that oscilloscope, and you can find them much cheaper than that on places like ebay.


http://www.ebay.com/usr/workingman.mv?_ ... 2749.l2754
I purchased mine from this seller, and it was packed well and had been serviced. I think he is in Missouri. He currently doesn't have anything for sale but a good friend of mine and tech pointed the unit out to me. You can find all types of used and off-brand scopes as low as 20 bucks, with no guarantees of course.

Eric

Thanks Eric for the advice, but currently as for the money it looks desasterous to me.

But one important question:
It looks like you picked up the audio signal on the output.
It is more important to see the shapes after having picked up the signal directly on the oscillator board before having been "influenced" by anything coming after ?