Minimoog Glide question

[thealien666]

Hello all. I've finally got my hands on a Mini ! Woohoo! It's from 1975 and in good shape. It needed a little TLC but mostly cleaning, as it was in storage for many years. That Pratt-Read keyboard action is great, but not the contacts underneath. What a nightmare. I'm seriously considering replacing it with Kevin's Opto-Key board, since a lot of the little "gold plated" springs are corroded. But at $500+ (I'm in Canada) I don't have any money left to buy it yet...I've spent all my money on buying the Mini ! And the original keyboard is finally fully working now (after 3 days spent cleaning the buss bars and contacts), albeit with the occasional glitch.

My question concerns the glide. It's working fine but I've noticed that the "up" time is not the same as the "down" time, regardless of the knob setting. From the lowest note up to the highest on the keyboard with glide full on it takes 2.6 seconds. But from the highest note to the lowest it takes 4.2 seconds. And when turning down the glide pot, these times are proportionally reduced, with the down glide about twice as long as the up glide. Was it meant to work like this from the factory ?

Thanks for any info.

Al.

[MC]

yes that's normal and is one of the "charms" of the minimoog

[thealien666]

Thanks, MC. That answers my question. I just wanted to make sure mine was working as intended. Indeed another charm of the Mini.

[Kevin Lightner]

Fwiw, I may offer a kit for the OptoKey at a substantially lower price, but it would be targeted only for experienced techs and engineers.

MC is right- the glide times are usually unequal.
The circuit can be modded to be more equal, but most people don't care or notice unless they're making siren sounds.
You have a good ear.
Congrats on getting a Mini!

[andibhatt]

Thanks for the info !!!!

[thealien666]

Fwiw, I may offer a kit for the OptoKey at a substantially lower price, but it would be targeted only for experienced techs and engineers.

MC is right- the glide times are usually unequal.
The circuit can be modded to be more equal, but most people don't care or notice unless they're making siren sounds.
You have a good ear.
Congrats on getting a Mini!

Thanks Kevin. I'll leave the glide as it is. It doesn't bother me, it's just that I wanted to make sure my Mini was operating correctly.

I would be really really interested by your OptoKey kit, since buying the Mini was rather expensive and the keyboard contacts show their age with some springs corroded despite the gold plating.
As I've already told Monica, your wife, in private e-mails I'm an electronics hobbyist and have already successfully built kits in the past.

At one point, I had even built myself (created) a "thumbtack synthesizer", as I called it. Simple octave divide-down circuits providing square waves, perfectly tuned, and a novel way of playing it: the musician had to wear a metal bracelet connected to a low sensitivity input (line in) of an amp, and he would simply touch gold plated thumbtacks with his fingers to play the notes. Since the output of those chips was about 15 volts (peak-to-peak) it even gave you very slight electrical shocks if your fingers were damp ! Hahaha. Those were the days... I was about 15 years old then, I'm 46 now. If I remember correctly the chips I used were : S50240 top octave and 7X CD4024 providing a full 8 octaves! (I had only connected 4 of them as a prototype). My father had even built a wooden casing similar in shape to a Païa for it. It sounded pretty good, for square waves...and was fully polyphonic !

Simply get back to me via e-mail for the OptoKey Kit. (your wife has my address, since we've already talked about it for the past few days)

Thanks again, and take care!

Alain.

[Kevin Lightner]

Heh.. if you blew out that 50240, you can buy that polymoog IC being sold in Germany for 60 euros!

Serious questions I have about offering kits tho:
Are you confident of soldering in surface mount components?

A question for anyone: Do you think most people could handle fine SMD soldering?
The DAC on the Optokey costs $15 alone.
I'd hate to see people ruin kits or expensive parts.
Or is this what kit builders find challenging?
Do I let kit builders try their hand at SMD soldering, perhaps for the 1st time ever?
I often lose a small capacitor or resistor when doing fine work like this, but I have extras.
What happens when someone loses a part like this?

I could supply a kit with the SMD parts pre-installed and tested too, I suppose.

Perhaps I should just sell the kits as blank boards, a pre-programmed MCU and provide a parts list and let the builders buy their own parts?

[thealien666]

...I could supply a kit with the SMD parts pre-installed and tested too, I suppose.

I think this would probably be the best solution, along with everything else included (components, preprogrammed PIC, mounting brackets, etc) as a complete kit.
From what I've seen, that little DAC daughter board is the only SMD equiped one in this project, right?

[Kevin Lightner]

From what I've seen, that little DAC daughter board is the only SMD equiped one in this project, right?

Yeah. It was conceived later and kind of added on to the main board.
It replaces a now-abandoned 14 bit DAC.
I know it looks tacky, but that little daughter board has a 16 bit DAC, 6.2v ref IC and a precision opamp.
I just couldn't fit all of that on the original board drawing and so went vertical.
If another rev was ever done, I'd do it all over purely in SMD and have the parts placed and soldered by machine.
There's something really fun about assembling a kit tho.

Thanks for the input.I appreciate it.

I now have about 15 of OptoKeys assembled, calibrated and tested, but still not finished with installation instructions, let alone assembly instructions.
Technical writing just isn't my forte.

So in the meanwhile, I've been installing them on Mini actions sent in.
I do all the installation and send it back. No complaints yet.