Many questions!
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Many questions!
Hi all, I'm brand new to this forum and also to the world of the Minimoog.
Ok here goes!...I have taken possession of a model D. It was last used about 30 or so years back, I'm in the process of renovating it and have a few questions. Rather than ask too many straight off the bat I'd like some info regarding a couple of mods it's had.
It appears to me that it has gained 2 or 3 toggle switches (see pics). I wonder if anybody's seen these mods before?
Where there should be 2 jack sockets on the left controller module there are 2 rotary controls! Any ideas?
Also, while I do have sound it is constant IE. play a note and it plays constantly until another key is played and then that tone/note plays continuously. I'm confused..
I've attached some pics of the areas. Any help or advice would be gratefully received.
Geoff
Ok here goes!...I have taken possession of a model D. It was last used about 30 or so years back, I'm in the process of renovating it and have a few questions. Rather than ask too many straight off the bat I'd like some info regarding a couple of mods it's had.
It appears to me that it has gained 2 or 3 toggle switches (see pics). I wonder if anybody's seen these mods before?
Where there should be 2 jack sockets on the left controller module there are 2 rotary controls! Any ideas?
Also, while I do have sound it is constant IE. play a note and it plays constantly until another key is played and then that tone/note plays continuously. I'm confused..
I've attached some pics of the areas. Any help or advice would be gratefully received.
Geoff
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- Posts: 10
- Joined: Tue Jan 17, 2017 11:27 am
Re: Many questions!
Update: The continuous tone is a function of the toggle switch above the oscillator modulation switch. So that's that one solved.
I now have this odd problem that osc 3 stays on on frequency IE: whatever key is pressed first dictates the tone regardless of what key is pressed next but this is only on osc 3. The other two behave correctly.
G
I now have this odd problem that osc 3 stays on on frequency IE: whatever key is pressed first dictates the tone regardless of what key is pressed next but this is only on osc 3. The other two behave correctly.
G
Re: Many questions!
The toggle switch next to the external audio in gain might use the well known, normally external cabled, self feedback track.
Switching the audio output to the external in and the activated external input volume used to overdrive the mixer and filter.
As these mods were normally done only on a very few or single instruments, they do vary in layout of the controls and the features.
Switching the audio output to the external in and the activated external input volume used to overdrive the mixer and filter.
As these mods were normally done only on a very few or single instruments, they do vary in layout of the controls and the features.
keep on turning these Moog knobs
Sequence:
Prodigy * minimoog '79 * Voyager * MF102 * MF103 * MF104z * MP201 * Taurus 3 * Minitaur * Sub Phatty * MF105 * Minimoog 2017+ MUSE * One 16
Sequence:
Prodigy * minimoog '79 * Voyager * MF102 * MF103 * MF104z * MP201 * Taurus 3 * Minitaur * Sub Phatty * MF105 * Minimoog 2017+ MUSE * One 16
Re: Many questions!
Figuring out the mods might help if we could see behind the back panel and under the modulation section.
Learn To Fix
Moog T1 Pedal Contact Board Upgrade: http://www.minimoog.net/daphne/moog-tau ... act-board/
Moog T1 Pedal Contact Board Upgrade: http://www.minimoog.net/daphne/moog-tau ... act-board/
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Re: Many questions!
Ok thanks guys.
The story has changed a little in as much as I've been reading the manual and this has demystified a lot.
That said I'm still a little confused with some of the mods. I'll get some pics of the internals up as soon as I can.
In the meantime...thanks again.
G
The story has changed a little in as much as I've been reading the manual and this has demystified a lot.
That said I'm still a little confused with some of the mods. I'll get some pics of the internals up as soon as I can.
In the meantime...thanks again.
G
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- Joined: Tue Jan 17, 2017 11:27 am
Re: Many questions!
Thanks Luckyluckynerd wrote:Figuring out the mods might help if we could see behind the back panel and under the modulation section.
Ok I've attached two pics of the mod behind the modulation section. It looks like whoever did the mod used a knife and fork to do it!
I'm thinking of either removing it and re-fitting the jack sockets or making a nicer job of the mod on tag-strip for example.
Any thoughts?
G
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- Joined: Tue Jan 17, 2017 11:27 am
Re: Many questions!
Thanks till,till wrote:The toggle switch next to the external audio in gain might use the well known, normally external cabled, self feedback track.
Switching the audio output to the external in and the activated external input volume used to overdrive the mixer and filter.
As these mods were normally done only on a very few or single instruments, they do vary in layout of the controls and the features.
Excuse my ignorance, I'm completely new to this (I'm liking it) are these toggles factory mods or more likely done by the previous owner?
I've now tested it by reading through the manual and it seems to be working as it should although I think it may need some calibration.
Geoff
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- Joined: Tue Jan 17, 2017 11:27 am
Re: Many questions!
Here are some shots from behind the front panel..(switches are indicated)
Re: Many questions!
This looks not like a factory modification.Old Scotty wrote:Excuse my ignorance, I'm completely new to this (I'm liking it) are these toggles factory mods or more likely done by the previous owner?
Most modifications that involved additional switches and knobs are very likely done by some technician or a musician. And not by Moog or a Moog technician.
And some of the pictured modifications appear not being done well.
keep on turning these Moog knobs
Sequence:
Prodigy * minimoog '79 * Voyager * MF102 * MF103 * MF104z * MP201 * Taurus 3 * Minitaur * Sub Phatty * MF105 * Minimoog 2017+ MUSE * One 16
Sequence:
Prodigy * minimoog '79 * Voyager * MF102 * MF103 * MF104z * MP201 * Taurus 3 * Minitaur * Sub Phatty * MF105 * Minimoog 2017+ MUSE * One 16
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- Posts: 10
- Joined: Tue Jan 17, 2017 11:27 am
Re: Many questions!
I thought as much. The work looks nasty, I'm going to make the connections much better.till wrote:This looks not like a factory modification.Old Scotty wrote:Excuse my ignorance, I'm completely new to this (I'm liking it) are these toggles factory mods or more likely done by the previous owner?
Most modifications that involved additional switches and knobs are very likely done by some technician or a musician. And not by Moog or a Moog technician.
And some of the pictured modifications appear not being done well.
Thanks G
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- Posts: 10
- Joined: Tue Jan 17, 2017 11:27 am
Re: Many questions!
Ok, I'm much more familiar with this Model D now.
Question:
The oscillators seem to fluctuate quite a lot. Any ideas? Capacitors perhaps?
Why is there a warm up time? I ask this because it is solid state after all.
Also I notice that the tuning adjusters have been modified. Were the originals regular potentiometers? (see pic)
Thanks for all your help so far.
Geoff
Question:
The oscillators seem to fluctuate quite a lot. Any ideas? Capacitors perhaps?
Why is there a warm up time? I ask this because it is solid state after all.
Also I notice that the tuning adjusters have been modified. Were the originals regular potentiometers? (see pic)
Thanks for all your help so far.
Geoff
Re: Many questions!
Trimpots have a limited life. As they age they can cause VCOs to drift. The ones in your unit are not original.
Don't replace any caps if they are original. The original polystyrene caps were designed to compensate for temperature changes and should remain in place.
Warm up time is required because the linear to exponential converter in the Minimoog VCOs contains a term in its transfer function that is impacted by temperature (read: the circuit is sensitive to temperature). The components warm up and eventually reach a steady operating point which the circuit functions at its optimal condition - accurate pitch tracking.
The other reason why Minimoog VCOs drift is the design of the system not just the VCOs. It takes more than replacing trimpots and caps. The power distribution must be corrected, reference biases must be redesigned, components with poor tempco specs replaced with modern ones, control sources must be redesigned.
Don't replace any caps if they are original. The original polystyrene caps were designed to compensate for temperature changes and should remain in place.
Warm up time is required because the linear to exponential converter in the Minimoog VCOs contains a term in its transfer function that is impacted by temperature (read: the circuit is sensitive to temperature). The components warm up and eventually reach a steady operating point which the circuit functions at its optimal condition - accurate pitch tracking.
The other reason why Minimoog VCOs drift is the design of the system not just the VCOs. It takes more than replacing trimpots and caps. The power distribution must be corrected, reference biases must be redesigned, components with poor tempco specs replaced with modern ones, control sources must be redesigned.
Gear list: '04 Saturn Ion, John Deere X300 tractor, ganged set of seven reel mowers for 3 acres of lawn, herd of sheep for backup lawn mowers, two tiger cats for mouse population control Oh you meant MUSIC gear Oops I hit the 255 character limi
Re: Many questions!
The original trimmers were wirewound and aren't made anymore. I used to sell them, but I sold off all my parts nearly 3 years ago. The mod done here is one approach to solving the problem of obsolete parts I've never seen before.
The electrolytic ones do need to be replaced. One of the ones in that mod in the first set of pictures is blue and looks blown already.MC wrote:Don't replace any caps if they are original. The original polystyrene caps were designed to compensate for temperature changes and should remain in place.
There's also 6 sets of 3 matched resistors on the right side of the oscillator board that benefit from being replaced. I'm in the process of making these kits again. I'm being gifted a good meter, which will speed up the process tremendously!MC wrote: The other reason why Minimoog VCOs drift is the design of the system not just the VCOs. It takes more than replacing trimpots and caps. The power distribution must be corrected, reference biases must be redesigned, components with poor tempco specs replaced with modern ones, control sources must be redesigned.
Learn To Fix
Moog T1 Pedal Contact Board Upgrade: http://www.minimoog.net/daphne/moog-tau ... act-board/
Moog T1 Pedal Contact Board Upgrade: http://www.minimoog.net/daphne/moog-tau ... act-board/
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Re: Many questions!
Hmmm interesting stuff.
I note that the main smoothing caps look a bit dodgy and thinking about it it's not a bad place to start.
I guess if the supply is flaky that might show down stream.(Ref osc varying)
Thanks guys
Geoff
I note that the main smoothing caps look a bit dodgy and thinking about it it's not a bad place to start.
I guess if the supply is flaky that might show down stream.(Ref osc varying)
Thanks guys
Geoff