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Korg Mini Pops 120 / Univox SR-120

      

 

Manufacturer Keio Electronic Lab., Corp. (Tokyo, Japan)
Date 1976 (according to schematics)
List price  
Sounds 6 (BD, SD, Cy/HH, low conga, high conga, claves)
Presets

16 (slow rock, swing, bossa nova, beguine, rumba, mambo, samba, waltz, tango, polka, foxtrot, march, rock 1 to 4)

Programmable no, but has rhythm auto change and automatic break/fill.
Controls

- tone balance control
- long/short fade out/in
- manual 'break' button

Outputs 2 (same signal)
Trigger out no
Footswitch 3 (start/stop, fade in/out, manual break)
Similar models Identical to the Univox SR-120. Similar to other Korg Mini Pops models, and to the Roland TR-66.

 

 

The Korg Mini-Pops 120, also rebranded as the Univox SR-120, was the top-of-the-line Mini Pops model produced, with more features and presets than other drum machines from this series, such as the Mini Pops Junior and 35. It comes in two cabinet styles, a tolex road case or a wooden chassis. Apart from their appearance, both units are identical in every other aspect. My tolex 120 came with a huge "Boss" sticker stuck on it... I couldn't remove it, I thought it was too funny, Roland being Korg's biggest competitor in the drum machine market at the time!

There are 16 presets, each of which has two variations, five "fill-in" settings that can be triggered every 2,4,8,12 or 16 bars, plus the ability to alternate between variations A and B of the selected rhythm. This change, and also the "fill-in", can be automatic or manual. There's also a fade out/in button, with a long/short setting. The unit has a mono output, and no trigger out. There are five jacks: hi-fi out, guitar amp out, start/stop, fade out/in, manual.

It has a raw sound, much rougher than Korg's next series, the KR-55/KR-55B drum machines. Basically the sound voices are still very "first generation", similar to the Rhythm Aces, although with more options for variation. The closest Roland drum machine to this unit, at least in terms of features, is probably the TR-66 Rhythm Arranger.

 

 

Below are some instructions on how to modify the unit for separate outs, some troubleshooting information, a copy of the owner's and service manuals.

Korg Mini Pops 120 Owner's Manual

Korg Mini Pops 120 Service Manual

 

>>> Rhythm pattern storage


The first thing to mention is that this unit stores its presets on a ROM chip, which is pretty much impossible to replace unless you rip it from another machine. Older drum machines, such as the Ace Tone Rhythm Ace series, stored their presets with an array of discrete components, which means that they can pretty much always be repaired if one's willing to put some time into it.

Not so with the Mini Pops 120 (and many others, such as the Roland CR-68). When I bought my first one, for a very cheap price, I quickly found that everything seemed to work, including all the voices and buttons, but every preset output the same thing: one hit on every beat, albeit with different voices depending on the preset. Obviously the rhythm patterns were lost either in the ROM chip, or somewhere on the way to the voice generator board. After quite a lot of poking around, I came to the conclusion that the ROM chip wasn't outputting the rhythm patterns.

 


Mini Pops 120 main board. The ROM chip is the big white one.
(Click to enlarge)

I must say that I'm not 100% sure that the chip is dead, as I'm not very experienced at digital electronics troubleshooting. But I'm pretty sure that's where the problem lies. So if you're planning to buy a drum machine, and the seller tells you everything works except all the beats are the same, be warned: it might not be an easy fix...

 

>>> Leaking capacitors


Fortunately, the second unit I bought still had intact patterns, but the cymbals and hi-hat sounded terrible, more like a farting overloaded speaker than a hi-pitched ring... A detailed inspection of the insides revealed the problem: all the 100mf electrolytic capacitors on the main board had leaked, in some instances damaging the traces and cutting some connections. The other value capacitors were OK, so probably the 100mf caps came from the same defective batch. If that's the case, my Mini Pops 120 is probably not the only one with this problem.


The culprits. Note the acid leaking around the leads.


Damaged traces (center of image). Two of them had stopped
conducting completely.

After I'd replaced the leaking caps and restored the severed connections, I turned the Mini Pops back on and my cymbals came out loud and clear, just as they were supposed to be. My unit was back to normal, so I turned my attention to getting individual outputs...

 

>>> Korg Mini Pops 120 separate outputs modification


After poking around for a while, I found patch points for all the sounds, and decided to rewire all five jacks with individual voices separated like this:

    • Bass drum
    • Snare
    • Cymbals / Hi-Hat
    • Low and high conga
    • Clave

I had a bit of trouble isolating the bass drum from the other voices, but by turning the tone knob all the way down, I could barely hear the other voices, so I decided to go with it. I had found some louder, more isolated bass drum taps on the circuit board, but they had a very different tone and attack, not very pleasant. They probably needed to be damped by other parts of the circuit, so in the end I went for the tap with the best tone.

 


Individual voice tap locations.

By tapping all the sounds from the locations above and routing them to the five jacks (wire low and high congas to the same jack), be aware that the main volume, balance and fade out/in controls become useless. I don't plan to use them so it wasn't a problem for me to lose them. I might actually convert those unused controls to something else in the future, for example wiring them to the conga tone or noise level pots inside...

 

 


Kneelz

Tue, 07 Dec 2010 14:22:51 -0800
 

Today i received my minipops 120 with dead ROM-chip.
I tried a tr606 trigger out on the pins of the ROM socket and all six voices came trough the output.
Too bad the output volume is very low and i tried it without the ROM.
The voices will be thrown out with an acceptable volume but only the bassdrum and claves will work.
It's time to do al little measuring but i'm sure this thing will work perfect with external triggers.
Thanks in advance for the individual output locations, i will definitely place them in mine.
I think there's also an easy way to put some extra mods on it(there are a lot of trimpots inside).
 


rond

Thu, 09 Dec 2010 09:01:20 -0800
 

ah daar is niels ;-]]
 


JVC

Wed, 30 Mar 2011 11:00:49 -0700
 

Hello, great post! I saw Mini Pops 120 demo on YouTube, and it sounded noisy (white noise on the background.) Is it normal?
I like old drum machines, please keep it updated & post more!
 


René S

Fri, 13 Jan 2012 12:07:14 -0800
 

Hello, your are a genious. The world listens to you and follows your advice. Got a Korg Mini Pops 120 recently, just sounded da da da, as you described it. I replaced a capacitor, fixed a trace on the top side of the board and now it works as well as the unit on youtube. You saved me a lotof time. Many thanks from Winterthur/Switzerland
 


Mike

Mon, 06 Feb 2012 06:10:36 -0800
 

Great Tipps,great Side, Thanks !
Do you know where the Point(on the PCB) is, for Trigger the MP 120 via extern Analogclock?

Cheers,
Mike
 


Phil Raines

Fri, 16 Mar 2012 02:53:14 -0700
 

Have you worked out a way to clock into the minipops 120 to dictate tempo. Be it through a cv gate or via midi?
 


bunnycat

Thu, 05 Apr 2012 14:27:46 -0700
 

If any of you have added external triggers to each voice, could you please let me know what trigger voltage and polarity to use? Thanks in advance...
 


Jan

Thu, 21 Jun 2012 08:31:16 -0700
 

Several links on this website don't seem to work. Right link to the large picture of the mainboard: http://estecho.com/gear_pics/korg_minipops_tolex_inside3.jpg
If the manuals above do not download, try a different browser (i.e. Firefox).
All downloads can be found here: http://estecho.com/manuals/
 


ESTECHO

Thu, 21 Jun 2012 18:23:49 -0700
 

@Jan
I've fixed the broken link for the pic, thanks for pointing it out. As for the manuals, I don't know what could be wrong, the download works fine for me in IE and Firefox.
 


Jan

Sat, 07 Jul 2012 06:12:08 -0700
 

Thanks Estecho, I'm sure it's caused by the parentheses in the file name.
 


SERPENTS

Sun, 05 Aug 2012 04:01:22 -0700
 

hi

just bought a 120 minipops for cheap sold as dead.
It had the problem you told about dead ROM; all instruments
playing on each beats.

First I was mad cause I've read your post but
after some measurment I've find that the Rom was not
electrically fed.

Due to electrolitic caps leakage, it has cut the trace from
power supply (the -5volt on the schem) which go
to the VSS pin of the ROM chip.
The trace was not physically broke but the leakage had
made the trace darker(color).

now it works like a charm, all preset rythms came to life.

I've modded it to have extrenal trig 2"4"8"16".
run whith my poly61 portamento good.

thanxx for your infos on this machine and the others.
cheers
 


PETER

Thu, 16 Aug 2012 00:31:12 -0700
 

@SERPENTS : Thank you very much for your information. Had my M120
checked after it went "playing all instr. on all beats"
Leaking elco's were exchanged and polluted traces cleaned & now it's indeed back to life :)))
And thank you, Estecho, for this ever so informative site!
 


ESTECHO

Thu, 16 Aug 2012 18:09:33 -0700
 

I've had many reports such as the ones above that indeed the ROM chip might not be the culprit when all the programs are lost. This is great news! I haven't checked mine since I wrote this page, but I'm happy to say I was probably wrong in evaluating the cause of my Mini Pops' failure. There is hope! :-)
 


Peter

Wed, 26 Sep 2012 09:03:30 -0700
 

Thanks a lot, fixed mine as well !
 


ESTECHO

Sun, 23 Mar 2014 18:42:31 -0700
 

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