Tag Archives: Electronic Music

KORG SQ-10 Analog sequencer, DIY repair

I recently discovered to my horror, that my sequencer, the old KORG SQ-10 could no longer be synced to MIDI through the KENTON Pro2 MIDI/CV interface’s ARP CLOCK signal, as I used to always do.
With the useful MS-50’s VU meter, I could see the interface voltages arriving in good health, but no way, the old sequencer didn’t want to go back to work and follow the sync signals.
Time to get back to the action with another “on the field” and completely DIY repair!

Opening an instrument of almost 40 years ago is always pretty annoying and time consuming! If there is something that certainly demonstrates the evolution made in hardware production, it is, apart from the standardization, certainly hardware and enclosures design:
Old machines often have enclosures that take a lot of time to open and inspect for maintenance. The KORG SQ-10 ANALOG SEQUENCER, has an infinite number of small screws to align with the frames and it is very easy to go wrong and have to disassemble a panel again to make everything fit. It is certainly better to have an electric screwdriver and a lot of patience.

At a first analysis of the circuit board, no current could reach the negative 7.5v rail test point. Restored the voltage after having changed a couple of power transistors and electrolytic capacitors, with disappointment, I noticed the sequencer still couldn’t sync to the trig sent by the Roland TR-808 electronic drum machine. It has been necessary to swap some transistors, replace some electrolytic capacitors and check a few integrated circuit chips, in the areas of the CONTROL and RESET circuit, to have back the sequencer to syncing to the main trig, mission accomplished! :D

Testing the machine a little further, I discovered a very interesting function, I had never tried before:
By sending the ARP CLOCK signal in the START / STOP jack, instead of the usual STEP input and selecting the second loop mode in the front panel, it is possible to loop a variable number of notes, all in the same time interval (one beat), up to the maximum of 12 steps. This allows, to play with unusual and odd sequences, still being always synced in time.
The CLOCK SPEED LINEAR IN jack allows you to control the number of notes emitted, remotely. By connecting it to an LFO or an envelope generator, it is possible to create really complex patterns.
Really an excellent analog sequencer, KORG should consider building a remake of the SQ-10, soon!

NAVA, DIY Roland TR-909

Nava DIY Roland TR-909
NAVA Roland TR909 clone

Done, it is finally alive !!!
Ufff, it took me a lot of time, but surely it was worth it! Finally, I have in my hands a Roland TR909 as in the old days. The sound is identical because this is a real clone, the appearance not precisely the same, but similar enough to fade the memories and fully create the illusion.

I bought the kit two or more years ago, but because of some laziness to start a project of this size and the delay to reorganize and restore the studio, which could no longer be postponed, I only had complete it now.
The NAVA is a clone of the classic Roland TR-909 drum machine, offered by the e-licktronic site in the DIY kit form:

Nava DIY Roland TR-909 internal circuits
NAVA 909 insides

The kit consists of the motherboard and an I / O card, plus a series of transistors and ICs, which are obsolete and therefore difficult to acquire. It is necessary to buy a large list of components, but there is a BOM with a link to Mousers where a prepared trolley is already present. The project is quite complex, given the number of components and their density. The construction is even more complex as the connection points and the relative exposed copper are really tiny, forcing during the building, to never lower the attention.

Nava 909 motherboard

In fact, despite the many years of experience in DIY and the needed careful attention, the construction was not entirely easy.
At the end of the project, after days (or in my case weeks) of work, the crucial moment is always to push the ON switch and verify the presence of “life” in a new assembly. Unfortunately, this time after loading the software and verifying that the sequencer was working, I noticed that the HH was not present … OMG impossible to stay too long without that emblematic OH!
While I have no problems with the construction, not having studied electronics, diagnosing a failure is for me always a nightmare. This time, I was able to put into practice some techniques I learned on how to use the oscilloscope to trace failures. The culprit turned out to be a five pins transistor, the old 2SA798 quite difficult to find, at reasonable prices. I’ve been able to emulate it, using a couple of matched BC560 transistors, soldered together.

Nava DIY 909 clone assembling
NAVA, Roland TR-909 drum machine clone


With the imminent arrival of the Behringer’s 909 and the Roland virtual analog reissue, we will soon be invaded by clones of this vintage drum machine, which will perhaps cause some of the magic of it, to be lost. BTW assembling with your own hands a piece of electronics with which playing music and having fun, is one of the greatest satisfactions a synth-nerd can experience. In my case, I have in my hands an electronic drum machine that I had loved a lot but then sold to switch to the, in those times new, PCM technology (a Korg DDD-1) and in the following years could no longer buy it because of the crazy prices of these units in the second-hand market.

Assembling the NAVA 909

Below you will find some of my tracks recently released, using the NAVA Roland TR-909, thanks for listening: