[sdiy] Concertmate MG-1 mods/schematics

[Michael Ruberto]

i apologize that the link to the schematics is no-longer working but 
xoom.com doesn't exist anymore. someday i'll get a new site up with these 
schematics and all the others that were there.

~M

>From: KA4HJH <ka4hjh at gte.net>
>To: "DTK" <aurastar77 at home.com>
>CC: synth-diy at dropmix.xs4all.nl
>Subject: Re: [sdiy] Concertmate MG-1 mods/schematics
>Date: Wed, 9 Jan 2002 04:53:22 -0500
>
> >Hello from the new guy :)
>
>Oh no, not another one...  8^D
>
>
> >I've got an MG-1 that I found at a pawn shop and resurrected. Man, do
> >I wish I had found this group about 6 months ago! :) Anyway, it's now
> >in good working order, and I've made several mods to it, installed a
> >MIDIJack, etc.
>
>At least it's working. Did you get all the decomposed foam rubber scraped 
>off?
>
>
> >For my next mod, I've decided that I want to try and slow down the
> >LFO rate. If I understand correctly, the LFO in this machine is just
> >another VCO.
>
>It's a simple triangle/square manually-controlled oscillator.
>
>
> >There's a slider type variable resistor for the rate
> >control, where lfo rate increases as resistance decreases. SO I was
> >thinking that I could just insert an extra resistor in line and that
> >would slow things down.
> >
> >Of course not... that would be too easy, wouldn't it? :) I tried it
> >out, soldered a 22k resistor in at a couple of different points, but
> >there was no change (as far as I could tell, anyway)
>
>Way too small a resistor. The frequency pot is 1M ohm, audio taper. You'd
>need another megaohm to cut the frequency in half.
>
>A simpler approach would be to increase the capacitance of C25 (6.8uF
>@16V). All you have to do is put another cap in parallel and switch it
>in/out with a SPST switch.
>
>
> >Is anyone here familiar enough with this little quasi-moog to help me
> >out? I'm really not even sure if I have the right idea or not. I've
> >been using schematics for the Rogue, which is (supposedly) nearly
> >identical in design. I've been unable to find any schematics or
> >technical information about the MG-1 online, so if anyone knows where
> >I can find anything, please let me know.
>
>Some schematic scans are here:
>
>http://world.conk.com/world/indridcold/synthfrm.htm
>--
>
>Terry Bowman, KA4HJH
>"The Mac Doctor"
>
>"By the end of Chuck Statler's 'Rock Videos' of Devo we agreed that even if
>Devo did not take the stage it was still the best concert any of us had
>ever attended." --Kim Thayil (Soundgardern), 1995




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