problem with osc 3 octave (tuning)

[steevio]

i have an intermittent problem where my voyager goes suddenly out of tune. it seems to happen when the synth has been on a long time, like most of the day.

on further investigation i've found that its Osc 3, and if i retune Osc 3, it will be way sharp in the octave above and way flat in the octave below. its like the range of the osc has stretched.
once or twice when it happened, it seemed to reset when i switched it off then on again, but now it is staying like this,

anyone had this problem or got any ideas ?

thanks in advance
steevio

[thealien666]

Possible intermittent contact in one of the internal trimpots adjustments for OSC 3 maybe ?

[steevio]

thanks 'thealien666'

i'll check out those trimpots

[thealien666]

thanks 'thealien666'

i'll check out those trimpots

I would gently tap on each one while listening to OSC 3 and see if there's any slight change in pitch, and to possibly locate one that is flaky, maybe due to bad internal wiper contact or possibly a cracked solder joint around one of its legs. But then again, it might be something else completely...

I would NOT try to turn any trimpot, since this could result in having to retune the whole instrument!!!

[steevio]

thanks 'thealien666'

i'll check out those trimpots

I would gently tap on each one while listening to OSC 3 and see if there's any slight change in pitch, and to possibly locate one that is flaky, maybe due to bad internal wiper contact or possibly a cracked solder joint around one of its legs. But then again, it might be something else completely...

I would NOT try to turn any trimpot, since this could result in having to retune the whole instrument!!!

could i ask why you wouldnt try turning a trimpot if it was obviously the one causing the problem ?

why would one pot detune the whole synth ?

my guess is that the trimpot is likely to set the range for the osc, and would only affect that osc, turning it might clean the contact and save sending the synth for repair, its got to be worth a shot, hasnt it ?

or not ?

[thealien666]

I realize that my previous statement could be confusing, sorry. Let me clarify that...

My warning was for someone who would have the very bad idea of trying to move each trimpot, one by one, until they would stumble upon the one for OSC 3 range.

If you have a means to identify the exact trimpot that only affects OSC 3 range, and carefully and precisely mark its position prior to trying to move it, then you might get away with it.

But then again, you might end up with an even worst OSC 3 than you started with, if there's another underlying problem unrelated to that trimpot that is really causing the range of OSC 3 to be offscale.

[steevio]

its looking very likely to be trimpot RP14 which sets the high range.

its got a distinct spot where the frequnecy suddenly changes.
ive calibrated Osc 3 according to instructions from tech support, and i made sure that RP14 was set in a slightly different position away from the dead spot, but still in tune, and so far it seems fine.

the saga continues....

thanks for your help mate.

[thealien666]

You're welcome. I didn't realize also that you had obtained the tuning procedure from Moog. That would certainly help in adjusting those trimpots. Some of them are multi-turns, but some are single turn, and those can become problematic after resting in the same position for a long time.

Almost all the trimpots in my Minimoog D are like that (dead spot) but luckily after 37 years the tolerances of some components has changed so the trimpots no longer sit in the same position to have perfectly calibrated oscillators!

Cheers!

P.S. Did you have to prove to Moog that you were a tech in order to obtain, or did you sign a legal document that says that you are not allowed to publish or distribute, that Voyager tuning procedure?

[steevio]

no i didnt have to sign anything, actually the information is easily found on the web anyway.

it was a single turn pot that was the dodgy one.

ive had the RME running for three days now with no problem, it might be worth not trying to replace the iffy pot, best leave well alone now i think.

[thealien666]

...actually the information (tuning procedure for Moog Voyager) is easily found on the web anyway.

Huh? Where ?
For the Minimoog Model D, yes. But for the Voyager, I haven't been able to find anything yet... Maybe I'm not looking in the right places ?