KORG SR 120 MINIPOPS CLOCK IN?

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pigsnoot
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KORG SR 120 MINIPOPS CLOCK IN?

Post by pigsnoot » Sun Jul 19, 2020 3:38 am

Anyone ever successfully installed an external clock in to the Korg Minipops 120?

There's this : https://tubbutec.de/blog/korg-minipops- ... tallation/ but that's about it , can't seem to find anyone who ever installed it.

Also Looking for clock input mod for Korg KR33. No service manual to be found...

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FactoryDefault
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Re: KORG SR 120 MINIPOPS CLOCK IN?

Post by FactoryDefault » Fri Jul 31, 2020 2:04 pm

I had plans to perform this mod at some point but backed off once I realized that it involved cutting traces.
If I ever regain motivation, I will post results here. That tubutec page is definitely a good starting point. You want to feed a clock into the junction point that is normally fed into the divider ICs. Start off by putting a scope in that part of the existing circuit to see what the clock looks like. I would add some sort of buffer.

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thispoison
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Re: KORG SR 120 MINIPOPS CLOCK IN?

Post by thispoison » Fri Jul 31, 2020 4:18 pm

I've chickened out on my SR 120 in case I ruin it. And my TR-77, my KR-33 and Auto vari 64.

Looks simple on youtube, but I've only built a few kits. Damn, I'm even scared to repair my CR-8000 buttons!

Man's gotta know his limitations.
Where have I seen you before?
Same place you saw me, I expect.
I've got a good face for memories.

https://soundcloud.com/thispoison-1

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FactoryDefault
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Re: KORG SR 120 MINIPOPS CLOCK IN?

Post by FactoryDefault » Mon Aug 24, 2020 1:52 pm

I’m pretty determined to solve this problem but unfortunately it’s not as simple as the Tubbutec diagram suggests. I did at least find a way to try that idea without cutting any traces. There is a via between the main oscillator section and the first divider IC. It’s an older style of via that looks like a small rivet and if you remove the solder from it, it breaks the connection to the trace.
Sending a clock into the divider IC did make sounds but it was almost like half of every measure was missing. I’m pretty sure the clock needs to feed more than that IC for the sequences to play properly.

So...I found all of the components that connect near the output of the master oscillator, lifted one terminal of each from the board and connected all of them to a breadboard so I could experiment with different places to connect a new clock. I currently have external sync working but need to add a run gate so I can reset all the flip flops when the clock starts.

I did not label my test wires yet so I couldn’t tell you where to connect the clock yet but this is next on my to-do list.

While I was waiting at the optometrist this morning, I also recreated the circuit in iCircuit so I could get a little more familiar with it.
98A0A3F9-78DC-48DF-BD31-DE7DCE303CB7.jpeg
AF30D2BE-C089-4E08-92F0-E604055B5FA4.png
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FactoryDefault
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Re: KORG SR 120 MINIPOPS CLOCK IN?

Post by FactoryDefault » Sat Sep 12, 2020 10:18 pm

Here we go. I added a couple of npn transistors.
They emulate the part of the circuit that I'm switching in and out.
I tried 2SC945 and 2N3904 and they both worked.
It's super easy to do on strip board.
minipops pcb sync points zoomed in.png
minipops pcb sync points zoomed out.png
Minipops add-on board.png
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