Moog Music Forum

Hello all,

I have a 1974 mini model d serial #3710 with new osc board. only problem is it is keyboardless... someone (whoever owned it previously) removed the keyboard assembly and cinch jones connectors and hardwired it to kind of work as a rack mount. I am looking to buy a keyboard assembly for this... I do have a pratt read key assembly from an Arp omni. but its jwire and i i have also thought about the possibliity of finding parts to convert it to a spring 2 buss version. So if anyone has a key assembly i would love to buy it! until then im going to try a kenton if its possible to use one in this situation... I added cv gate in/out and kbd out jacks .. I forgot to mention my mini is semi heavily modified.... sample and hold ,Rivera music systems lfo 4 , single and multi triggering, and rivera music systems distortion.. If anyone has any thought or knows of anything or if kenton will work for me or not please let me know ...!!

- john

so does anyone know of somewhere other than ebay know where i could look for a key assembly for a model d 1974 serial #3710?

also i added gate in/out and kbd out jack to my mini ( using the expanding
your minis patchability .pdf from the files section) how does this change my
controlability using a kenton on a mini that has a completely bypassed
keyboard?? ... i looked into the wiring a bit more and it looks like whoever
owned this previously removed all the cinch jones keyboard and mod whell
connectors and hardwired everything back together to bypass this completely.. I
just wanna be able to play my mini.. =) and if kenton can do it till i get a
keyboard assembly that would be great .. i can control the mini from my micron
or my o1/w or something. till then just wanna know if its possible now with
these added jacks.. =)

thank you
,
john

John,

Mini keyboards are dieing more and more frequently and there are no drop-in replacements available.
Finding another Mini action in good condition occurs very infrequently.
If someone put one on Ebay, you could be sure several people would be bidding against each other for it.

A two buss keyboard can be made to work, but you'll have to have a good understanding of Mini circuitry and be able to mod or make things as necessary to accommodate the differences.

For example, if the 2 buss keyboard you have uses diodes and isn't wired as a voltage divider, you'd likely have to completely rewire it.
This would involve 43 perfectly matched resistors wired in series.
Not a fun job, though you could probably get by with buying 0.1% resistors for more money. (about $1 ea.)
Still... a lot of work.

I have several Mini "scrapper" actions around, contacts, keys and other parts, but it would take considerable work to make a good reliable keyboard.
Doing it that way would cost a lot of money, labor-wise.

You could buy another Mini and swap things as necessary.
But again, lots of money to outlay.

I have even designed a replacement keyboard for a Model D that never needs contact cleaning (optical) and provides many new features including MIDI in and out, but I don't have the money to develop it as product.
I made a similar "never clean" replacement drop-in board for the Taurus 1 pedals, but the Minimoog design is much more involved.

So I guess my point is, there's no cheap solution I know of.
The keyboards are dieing and supply-and-demand ratios are widening.
You might have to wait or settle for what you've presently got.
I wish you good luck though.

Too bad about the mod section being removed also.. It seems as if that can mean you won't have the controllability you would have with a Mini that had Kenton installed, but I could be wrong. Minis are becoming more valuable and now days to find a part of a Mini will cost you a fairly decent amount. Depends on what you already have invested in the module itself. If you haven't got much into the module then you could afford to pay the premium to find the keyboard. It just seems like whenever I'm watching a part of a mini being sold, they go up fairly fast.

I wonder, the former owner who modded the heck out of that, how he controlled it?

heh well it does have the mod section.. its just rewired and hardwired only thing missing is a keyboard if possible ill post some photos.. as far as Kevin Lightner's response, i have an arp omni keyboard ( pratt read .. though it is j-wire) I had heard you can get parts from conn organs to rebuild such keyboards.. i would have to convert it to a spring action version i think parts will run roughly around 300-400$ .. bellcranks bussbars springs grommets etc. Ive just had a hard time trying to find a good picture of the pcb.. and or a good drwing of the circuit layout.. for the pcb board. as far as having a by passed keyboard will i be able to use kenton cv to control it externally?? the synth makes sound .. oscillators seem to hold tune pretty well... right now the best example i can give you of how it is working is like an octave cat.. if set on bypass mode.... ( turn the sustain up and the oscs will play and hold.. )and i can make noise but no tune.. ( no clue why some one did this to this synth.. lol the mods are pretty fun though
sample and hold and distortion ( rivera ) Lfo 4 and multi and single trigger which im not sure what they are for... I did add gate in/out jacks and kybd out jacks as per the old polyphony magazine mod from lords of the mini.. not sure how that helps my kentonability.

thank you for your responses! and further help would be great!
john

Here's the way I mod a Mini for external CV and Gate in.
Please note that I stock new edge connector pins and use them when performing this mod.

Extend keyboard CV from brown/white wire normally going to edge card pin 9A on board 2, to n/c switch on CV input jack.

Connect tip of CV input jack to a piece of wire.
The other end affix a new edge connector pin.
Insert into pin 9A of board 2.

Extend keyboard GATE from white/orange wire normally going to edge card pin 6A on board 2, to n/c switch on GATE input jack

Connect tip of GATE input jack to a piece of wire.
The other end affix a new edge connector pin.
Insert into both pin 6A and 20B of board 2 (or insert just to 6A and jumper R65 (pin 6A) to anode of CR10 (pin 20B))

Remove or snip the wire from the keyboard connector #5 (usually green) to the farthest (n/c) bussbar.

Replace R1 (590 ohm 1%) on board 2 with 50 ohm cermet multiturn trimmer and 576 ohm 1% resistor (50ppm or less) in series.
After Mini has warmed up and power supply calibrated, adjust keyboard to exactly 1v oct output using this trimmer.
(alternatively, you can use a 620 ohm fixed resistor for R1 with a 25K cermet trim across it.)
The keyboard will now be at exactly 1v/oct output.
Tune VCOs last.
Now the VCOs will be exactly at 1v/oct for external CVs also.

This mod cuts out the keyboard's CV and Gate and inserts your own.
The external CV then passes through the Mini's glide and is available on the orange filter keyboard tracking switches.

Also, Minis are in the key of F, where 1 volt in produces an F.
Most other synths are at C, where 1 volt produces a C note.
I'm not including the mod to automatically transpose the Mini from F to C, but otherwise this is how I will often mod them.

I also tend to replace all the summer resistors on the VCO board with newly matched precision resistors and often the same treatment is applied to the octave switch's matched resistors.
This increases their tracking and octave setting accuracies.
Some Minis used a dark blue style of 1% resistors that don't hold their values well over the year. The brown colored 1% resistors they often used tend to do better and remain more accurate.
The brown carbon resistors they used on the older Minis can be really off value by the way. I've measured some that were up to 40% off.
When found in the power supply section on older Minis, I tend to replace them with metal film 1% (50ppm drift.)
A voltage controlled synth is only as accurate as the voltages being provided.

Btw, I'm not a big fan of the Lords of the Minis site.
Much incorrect info and other good info I provided that wasn't credited.
When I see pics of Minis billed as "restored" still with 30+ year old caps in it, I tend to laugh. Minis weren't made with 30 year old caps.
Polishing the wood isn't restoration.
They even have me listed in their links as "Minimoog parts", even though I'm at well over 400 Minis serviced or restored - probably more than all of LOTM authors put together.

this is the mod i did for cv in/out and kbd out..

http://f1.grp.yahoofs.com/v1/YPe3SozUIE ... xpmini.pdf

dont know if this is a good mod.. lol i also forgot to mention this is a 1974 model d with old osc board replaced with a new osc board.. ( not a remake its the one with resistor networks and ua276's .

basically soldered wire from between pins 4-5 on board 2 to a jack and ground lugs together to rest of grounds on the jacks on top.. and a wire to another jack from between 100k resistor and diode off track to pin 20 on board 2.. easily undoable if another mod is better. =)

I figure if i cant have a keyboard id at least like to make this controllable by an outside source.

Im interested in knowing what kinds of key actions and parts you may have .. I am willing to do the work to get it to work, If it is possible..

once again ill try to take some good pics so you can see what im working with. =) thank you again for your quick help. =)

john

ok ive posted some pictures to flickr... here is a link i dont know how helpful they would be but might as well look

http://www.flickr.com/photos/81698114@N00/?saved=1

thanks,
john

Thanks for the pics.
Kinda ugly in there with all the electrical tape though.

One thing you should check and I didn't see in the pics was if the main power supply caps on the rectifier board are up to spec.

When Minis were first made, they used two 500uf caps.
Then they used 1000's and a 470uf for many, finally ending production making all three caps 1000uf.
If one puts in a later VCO board into an earlier Mini, these caps should be switched to three 1000uf caps like the later units.
That one VCO board draws more current than the rest of the Mini and needs the additional filtering offered by the higher 1000uf capacitors.

Otherwise, I don't know what to say.
If it was on my bench, I'd document the RMS mods, strip the whole thing down and build it back up correctly and with future service in mind.
That means either adding connectors or dressing wires of the mods for ease of service later.
The way it is now is kind of scary to a tech. At least it is to me.

ok thanks for that info ill have to check out my cap values..

So after seeing these pics do you think this would still be controllable by a kenton cv to midi?

everything works ( though cant tell if attack and decay really work since nothing is really triggering them)
but otherwise everything seems to be fine.

only other thought i have is maybe a moog 951 keyboard ( i know they are many more keys) but maybe i could rig something so its usable. I know the 951 was also a 2 bus keyboard as well.. and the 952 was single ( 2 note). just a thought let me know if you think this would work..

otherwise i might just spring for a kenton .. for the moment..

unless i find anyother option.

thank you very much Kevin you've been a great help and source of info.!

-john

It sounds like you're into DIY; how about a MIDIBox project?

http://www.midibox.org/dokuwiki/doku.ph ... nalog_gear

If you got a 951 or 952, I'd leave it stock and mod the Mini to accept the signals. Better than modding an original Moog modular keyboard.
You can power either keyboard off the accessory power socket of the Mini given the right connector and the signals from it would be compatible.

As far as internal Midi to CV converters, I prefer the Lintronics model.
Easier to install and offers a lot of features.
It was the one Bob Moog used to offer back in his Big Briar days.
I think Kentons require that one take a wood router to the underside.
That's kind of involved work just to add MIDI.

Also, if you have a Mini with the newer VCO board, built-in MIDI and some mods, please understand the power supply will be running pretty hot.
Although this won't affect the drift of the VCOs much, it can cause the VCF to drift some and even the VCAs can become a bit unbalanced.
Point is, it's more current than the Mini ever expected to push.
Since I'm seeing more and more of the power supply diodes dieing nowadays, you might consider replacing the four 1N4004 diodes with some that handle more current. Maybe 1N5404.

hmmm thank for the diode info .. well i was looking into the kenton mk2 pro solo i think it is an external unit...
Ive checked out the lintronics website a few times but there is no price info and site is really kinda confusing...makes it sound like id have to send my mini to german or something.
=)

john

kenton mk2 pro solo

I use one of these and have found it to be an excellent and accurate converter.
My only gripe is that some of the advertising literature regarding it states it can run on an internal 9v battery.
I opened mine and this just doesn't appear to be so.
Still, a very good converter.

ok sounds good , lol i guess the original question i wanted to know would be if this will run the mini since i have no keyboard.... can the kenton scale ( the F on the mini to a C? ) or something like it? if so ill get one and at least make my mini useful till i find a key assembly..

thank you,
john