Jupiter 4 Tuning
Posted: Sun Jun 22, 2014 11:30 pm
Hey guys,
i know a few of us have Jupiter 4's here..
was wondering how yours all hold up tuning wise?
Mine has always been a bit out of tune.
Today i decided to try and tune it - I warmed it up and tuned it nicely (using the 4 trimpots) - the scaling is almost perfect so i didn't want to mess with that (internal voice card trimmers). My psu voltages are all spot on (within tolerances set out in the service manual)
Thing is, when it's turned off, the next time the voices are all out either way by say 20 cents..
I could just tune it before every session (only took a couple minutes), but i would like to make it more stable.
Curiously - wikipedia says this about tuning - i can't find the article that this references:
[i]The VCOs can garner unstable tuning if aging or low-quality electrolytic capacitors are used (two for each voice card). Synthesizer repair shops can replace these tuning capacitors with stable polystyrene capacitors for an instant perfect tune. Individual oscillator card VCO tuning is accessed by four capped holes in the middle of the back of the case, but the unit should be allowed to warm up before adjusting for at least 20 to 40 minutes prior to adjustment.[/i]
Has anyone done this? i.e.: changed the 'tuning' caps for polystyrenes? and which ones are the tuning caps?
I'll eventually go through and re-cap all my synths, but i'd rather not pull it apart to do so unless i have to.
I'd be very curious to know how your Jupiters hold tune? and if you have recapped and noticed a difference etc. I've a desoldering station on the way, so it wouldn't be too hard.
i know a few of us have Jupiter 4's here..
was wondering how yours all hold up tuning wise?
Mine has always been a bit out of tune.
Today i decided to try and tune it - I warmed it up and tuned it nicely (using the 4 trimpots) - the scaling is almost perfect so i didn't want to mess with that (internal voice card trimmers). My psu voltages are all spot on (within tolerances set out in the service manual)
Thing is, when it's turned off, the next time the voices are all out either way by say 20 cents..
I could just tune it before every session (only took a couple minutes), but i would like to make it more stable.
Curiously - wikipedia says this about tuning - i can't find the article that this references:
[i]The VCOs can garner unstable tuning if aging or low-quality electrolytic capacitors are used (two for each voice card). Synthesizer repair shops can replace these tuning capacitors with stable polystyrene capacitors for an instant perfect tune. Individual oscillator card VCO tuning is accessed by four capped holes in the middle of the back of the case, but the unit should be allowed to warm up before adjusting for at least 20 to 40 minutes prior to adjustment.[/i]
Has anyone done this? i.e.: changed the 'tuning' caps for polystyrenes? and which ones are the tuning caps?
I'll eventually go through and re-cap all my synths, but i'd rather not pull it apart to do so unless i have to.
I'd be very curious to know how your Jupiters hold tune? and if you have recapped and noticed a difference etc. I've a desoldering station on the way, so it wouldn't be too hard.