KORG BX-3 & CX-3 stage organ thread

[Pepe]

Today I received a few replacement parts from the USA:



The white one is the replacement knob and it seems to fit perfectly. The knob is normally for vintage Roland synths (Jupiter-8) and drum machines (TR-808). It is very hard to find a matching knob for the KORG organ so I'll be happy with this white knob.

Of course I will replace all the eight tactile switches as well.

[Pepe]

Last night I swapped all the tactile switches and I reassembled the organ again. I think that the white knob doesn't look too odd and the eight switches now work properly again.





I hope the organ will get a more noble look with the black paint. I won't leave it as it is for sure:



Too bad: there are some minor flaws. The 5 1/3' and 1 1/3' drawbars seem to have bad solder joints and only come up from time to time in the "Drawbars" mode (in the presets they work fine) and I need to clean the contacts of F#4 again. And a really awful flaw is that the notes C1, C2 and C3 don't play the 1' drawbar tones - all other keys do. I don't know yet what's causing this problem. I hope it will vanish after cleaning/crimping the contacts.

[Pepe]

Finally I found the time to go on with the organ repair. Tonight I found out that one of the rather rare sound chips is faulty. I bought a replacement chip a few months ago, but it turned out to be faulty as well. I tried it with a working chip of my double manual KORG organ and - voilà! - it worked properly. Now I know what's wrong. I don't really like to invest another 50€ for a chip.

I'm going to paint the housing black in the next weeks and then let's see what I will do with it.

[Laurie]

[Pepe]

It's a Siemens SM305B - it was only used in organs in the '70s and '80s as far as I know.

[Dirk]

How about getting an old organ cheap from a 2nd hand store and using that as donor?

[Pepe]

The problem is that only a few organs had these chips on their circuit boards. And not all of these are of the cheap type. If you see someone who wants to throw away his self-built Dr. Böhm Top-Star DS, save the circuit boards, please!

[Pepe]

Last week I received a working SM305B IC (total costs: 46 EUR ) and now the organ's tone board works as it should. But there was a remaining problem: two of the drawbars refused to work properly and resoldering their connections didn't improve things. So I opened them up and in both cases the sliding contacts were loose. I glued them into position and it looks like a solid repair. A few minutes ago I assembled them together again. The multimeter says that I was successful. I will paint the chassis once more and put everything together tomorrow. Then we'll see if everything is alright - at last!

[The_Doc]

Great news Pepe. Everything crossed for you - good luck

[Dirk]

Well done!