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Korg Mini Pops 7 percussion module
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LektroiD



Joined: Aug 23, 2008
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PostPosted: Mon Jul 13, 2009 7:31 am    Post subject: Korg Mini Pops 7 percussion module Reply with quote  Mark this post and the followings unread

I'd like to build the percussion module out of this diagram. However, there is an NPN in the schematic with two circles around it. But in the legend (key) the transistor with two circles on is depicted as a PNP. I'm a bit confused which transistors are used and where.

I've not yet checked availability of the components at this stage, or if there are compatibles.

the full schematic can be found here:
http://www.jeanmicheljarre.pl/radek/samples/minipops.jpg


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LektroiD



Joined: Aug 23, 2008
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PostPosted: Mon Jul 13, 2009 5:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

If I'm reading my international transistor equivalents guide correctly, the following should be:
2SA564 = BC258
2SC644 = BC182
2SC828 = BC167

DOUBLE CHECK THE ABOVE!

I still have no idea what the transistor next to the bold '65Hz' text is though. it could either be 2SA564 (going by the two surrounding rings) or 2SC644 (going by the polarity).

Help would be a virtue right now Wink

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esnabez



Joined: May 01, 2009
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PostPosted: Tue Jul 14, 2009 8:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's the same section from the Univox SR-95 (same machine rebranded) schematic. As you can see, it's definitely a 2SA564(0).

Not to discourage you, but the 14 or so inductors that this machine uses are nearly impossible to find. Just a heads-up from someone who once wanted to build this circuit too.

I do own an SR-95, so if I can be of further assistance, let me know...


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beszedes



Joined: Jul 20, 2009
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PostPosted: Mon Jul 20, 2009 6:20 am    Post subject: Reply with quote  Mark this post and the followings unread

I also got that sch for MP7 but unfortunately it seems to be incomplete: a part is missing from the central region (rhythm section).

@esnabez: could you please send (or post) the entire schematics of the univox? thanks,

Btw, I think replacements BC183B and BC237B are OK.
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esnabez



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PostPosted: Mon Jul 20, 2009 11:07 am    Post subject: Reply with quote  Mark this post and the followings unread

beszedes,

I'm hesitant to post the Univox schematic, as it's part of a pdf service manual that I downloaded from musicparts.com. Although they are obviously not the copyright holder, they do put a lot of effort into their schematic/manual service.

That said, I've cleaned up the minipops schematic to reflect a missing part (1uF elec cap) and the missing connections...


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beszedes



Joined: Jul 20, 2009
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PostPosted: Mon Jul 20, 2009 1:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for that! Know, what I don't understand in this schematic is that where do some of the instrument's triggers come from, for instance TAM, QUI, GUI??
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esnabez



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PostPosted: Mon Jul 20, 2009 2:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes, I see what you're saying... I never noticed that before!

I checked the entire service manual, and it makes no reference to where the TAM, GUI, and QUI get their triggers. Being that they are always on (output controlled only by their volume pots), they must be hardwired to the rhythm generator SOMEWHERE!

I guess the only thing I can do is pop open my Univox and see what I find. Be patient, though; I'm super busy these days. I'll try to get to it by Wednesday...
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LektroiD



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PostPosted: Mon Jul 20, 2009 6:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

I would imagine the Guira uses Gate rather than Trigger, since the inbuilt sequences have different length notes (almost like a synthesizer sound). The Quidjada & Tambourine would work triggered (one-shot).

Correct me if I'm wrong, but if you look at the Korg diagram that I posted in the initial thread (you'll need to cross reference between the korg & univox diagrams for component numbers). It appears it is in fact a Gate signal input which goes to the collector of Q21 base of Q20. This also is also depicted with a square 'pulse' wave (on/off) symbol just underneath where it says (GUI).

It would be great to have an up to date 'clone' of the gui/qui/tamb, with the hard to find inductors substituted. Anyone know what would work as good substitutes?

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tonewill



Joined: Aug 21, 2009
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PostPosted: Mon Sep 21, 2009 8:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Did you get any further with this project?
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LektroiD



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PostPosted: Mon Sep 21, 2009 9:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Unfortunately not, without knowledge of what I could substitute for the inductors.
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tonewill



Joined: Aug 21, 2009
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PostPosted: Mon Sep 21, 2009 5:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

That's a shame. If we knew what other old gear they were used in maybe something cheap could be picked up on eBay.

I did a search for inductors. What is it about the new ones that makes them unsuitable as a replacement?
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andrewF



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PostPosted: Mon Sep 21, 2009 9:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

unusual to find inductors with values over 50mH these days
you could always roll your own
http://www.diygallery.de/DIYsites/inductor.html
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tonewill



Joined: Aug 21, 2009
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PostPosted: Tue Sep 22, 2009 4:10 am    Post subject: Reply with quote  Mark this post and the followings unread

andrewF wrote:
unusual to find inductors with values over 50mH these days

I see.
andrewF wrote:
you could always roll your own
http://www.diygallery.de/DIYsites/inductor.html

Interesting, thanks. I'll read through that, though somehow I think it's going to be beyond me, but maybe not LektroiD perhaps.

I had an additional reason for being interested in this. I just bought the Univox SR-95. Everywhere says this is a 're-badged' Korg Minipops but I didn't see anyone mention that the rimshot sound is missing and the cowbell substituted: ta ta ta CLONK ta ta, ta ta ta CLONK ta ta... Rolling Eyes. However, looking at the sound generator board you can see near the bottom centre a missing inductor (4H Shocked) with several other components around it missing. The pulse trigger wire below it is marked RS (rimshot) and when you put 5 volts across it it plays the cowbell sound. There is a CB pulse connector at the top of the board that you can see here (yellow wire) which plays the same sound. So, I reckon that adding the missing components and disconnecting the rimshot trigger to the cowbell, then the rimshot sound could be added.

Thought I'd share that, hope it isn't too off topic.


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SR-95 voice generator board
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Last edited by tonewill on Fri Mar 11, 2011 4:44 am; edited 1 time in total
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ickystay



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PostPosted: Tue Sep 22, 2009 8:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Those brown TDK's abound in old home organs. Organ Service Company sells them for $8 bucks each.

Go here: http://www.organservice.com/

click "Thomas", and scroll down to the 80- part numbers.

I have a half a coffee can full. tonewill, I'll give you a 4H if you want to pay postage. PM me.

edit- Adding schematic found on the internet.

edit again- oops, missed the schemo link in the first post. Oh well...


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tonewill



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PostPosted: Wed Sep 23, 2009 5:03 am    Post subject: Reply with quote  Mark this post and the followings unread

That's great news ickystay, I'll definitely PM you!

I've checked the RS components on that circuit diagram and they match the missing components on the Univox board, so that's even more encouraging.
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tonewill



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PostPosted: Wed Oct 07, 2009 9:35 am    Post subject: Reply with quote  Mark this post and the followings unread

Received the inductor from ickystay today Very Happy.

There's a diode in the rimshot circuit. The service manual lists only one type of diode for the sound generator board which is: WG. 713. Anyone know what that is?

Many thanks.

EDIT: this site says BAY 74, BAY 95, 1N4154, 1N4148...49 are replacements.

Found a 1N4148 here. If anyone knows whether this is okay or not, please let me know.

By the way, I feel I've hijacked this thread (sorry), I'll start another to show progress in case anyone is following.
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esnabez



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PostPosted: Thu Oct 08, 2009 4:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think your info is right. According to a semiconductor cross-reference book I have, a WG713 can be replaced by Radio Shack part # 276-1122, which are 1N914/1N4148 diodes.

Don't know what others think, but I don't feel you've hijacked the thread. For me it's nice to have all this MP7/SR95 info in one place...
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tonewill



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PostPosted: Fri Oct 09, 2009 7:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks esnabez! I appreciate you looking that up. I just need to sort out a few other components I need for something else I'm doing then I'll place an order. I'll post my progress here then if no-one objects.

Thanks again.
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LektroiD



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PostPosted: Wed Oct 14, 2009 10:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

esnabez wrote:
Don't know what others think, but I don't feel you've hijacked the thread. For me it's nice to have all this MP7/SR95 info in one place...


I have absolutely no qualms either, It's good to amalgamate as much info on the same topic into one thread, it's all relative.

That said, I was keen to get this project off the ground, but I have recently got major commitments in the music industry with a new recording contract, which has lead to another, and another. So, if someone else wants to pick this up where I left off, please feel free to do so, it will be a great little project.

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tonewill



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PostPosted: Fri Oct 16, 2009 3:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks LektroiD, good luck with the recording.

I'm expecting the components I need to arrive next week so I can try the 'rimshot' mod. Meanwhile, if anyone has the SR7 service manual pdf and would like to swap it for the SR95 service manual, please send me a PM. I need to compare the two to determine where the cowbell and rimshot triggers are linked. I'm hoping it's not under the rhythm selector switches. Also want to compare the circuit for the rhythms that are different.

Will keep you updated.
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tonewill



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PostPosted: Wed Oct 21, 2009 6:14 am    Post subject: Reply with quote  Mark this post and the followings unread

For those reading this who missed my previous posts, I'm adding the missing rimshot sound to the Univox SR95 that the Korg MP7 has. On the SR95 it is substituted by the cowbell sound. However, the tone generator circuit board is the same with some components missing.

'ickystay' very kindly sent me the required inductor that are hard to find. I've now soldered all the components in place. I also replaced all electrolytic capacitors, thought it was probably not necessary.

As you can see the inductor is the same as the originals.

I wasn't sure whether it had worked at first but that's because the rimshot is drowned out by the cowbell, as expected, but it is there Smile.

I now need to find out where they are coupled and I'm sure this is on the pulse generator board. I really need the layout of the MP7 board to look at now in order to determine where it differs from mine. I expect there's a jumper somewhere. I can't find the MP7 schematic at musicparts.com only the SR95 which I've already bought. Can anyone help with this?

Many thanks.


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Last edited by tonewill on Fri Mar 11, 2011 5:04 am; edited 6 times in total
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tonewill



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PostPosted: Sat Oct 24, 2009 6:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Alright, looks like no-one can help with the circuit layout. Anyone know how to remove the rhythm selector buttons and metal cage in a non-destructive way?
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tonewill



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PostPosted: Wed Oct 28, 2009 6:19 am    Post subject: Reply with quote  Mark this post and the followings unread

I'll update this just in case someone finds this thread one day while searching for info on adding the 'missing' rimshot sound to their SR95.

There are 2 through-board jumpers on the pulse generator board that connect the cowbell and rimshot together, one of these needs removing. If you're careful you should be able to pull one of them out with tweezers while melting the solder. I, on the other hand, pushed both of them into the board causing problems. I thought they were connected with a wire jumper.

The only way to fix this was to buy myself a solder sucker and remove the rhythm selection button 'cage' completely to get to the other side of the board.

It now works fine. I can post a recording if anyone wants to hear.

The next task then is to change the patterns to match the MP7 (in the name of something interesting to do). The schematic esnabez posted earlier showing CY1 (cymbal 1) and CL (clave) give a clue to what needs to be done I think.


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Where the cowbell and rimshot are connected
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Better to pull the link out from one of these two points on the other side of the board
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Last edited by tonewill on Fri Mar 11, 2011 5:15 am; edited 5 times in total
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esnabez



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PostPosted: Wed Oct 28, 2009 10:18 am    Post subject: Reply with quote  Mark this post and the followings unread

Congratulations on your success!!

Until this thread, I didn't even know there were differences between the Korg and the Univox. Thank you for sharing your hard work! And, I'd love to hear a recording if you get a chance...
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ickystay



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PostPosted: Wed Oct 28, 2009 12:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Looks like you are the pioneer in SR-95 to MP7 conversion. Congrads on your success so far!
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