Hi folks. I was just wondering if someone would be kind enough to give me a blow by blow account of how to tune a moog prodigy? The two oscilators on mine seem to drift out of tune as i go higher up the keyboard.
I have read the section in the service manual about tuning the prodigy but it is somewhat confusing as it mentions trim pots that are not labelled on the back of mine? Am i doing something wrong? I have range and scale trim pots for each osc. Not freg, range and hi-end?
Any help on this would be amazing
cheers
The trim pot for that is not accessible from the Prodigy’s little holes in the back . Those are just for tuning each osc… You must open it up… You need to find the trim pot that controls the volt/octave scale (which is what makes the keyboard track notes correctly- Also this is what we named our band after “The Volt per Octaves” !!) hehe
The crappy thing is you CAN easily tune that trim pot without taking out the board BUT first you have to know which pot it is.. They are all labeled on the pot side of the board.. Which means for this round you basically have to take the prodigy apart and find the trimpot.. In the service manual it explains this procedure but it says to use a multimeter to ensure that it is exactly 1 volt per octave from C - C (or from A - A for that matter).
But i did it by ear pretty easily. By tweaking it with prodigy’s power on and plugged into the speaker. I used A 1 and A 2 and kept hitting them back and forth til they sounded an octave apart.. Then check the rest of the keys and make sure that all octaves sound in tune with each other.
The trim pot is actually tweakable from both sides of the board, but like i said you have to know which one.. There are only a few trim pots that you tweak from both sides.. This is because underneath the trip pot a hole was drilled through the board, to access the little screw that is in the trim pot. So make note of which one it is and where it is located from the bottom.. That way if there is a next time, it will be easier.
You can just pop the bottom of and tweak it while you play, with out having to take anything else apart.
I would also tune each osc FIRST, independently from one another. Meaning turn off osc 2, when tuning osc 1 and vice versa. Also make sure before you do this that the FINE TUNE pot (on the prodigy’s main control panel) is centered ! Then make sure they are tuned together… THEN tune the V/O scale til it tracks properly..
It took me about 30 minutes to get all the pots in the right place before i was happy… But i did it by ear.. If you use a multimeter and follow the manual’s directions it might take less time…
Hope this helps…
R58 as per the schematic but i dont have a board layout diagram. Maybe the ident mask can be read from the bottom of PCB.
cheers 
http://www.hylander.us/images/schematics/moog/MoogProdigyServiceManual.pdf
and here for PCB layout and detailed tuning instructions
http://www.pmerecords.com/Tech.cfm