Month: June 2016

Finally, a MIDI interface for the ARP Omni 1 & 2 synthesizers!  This MIDI adapter is user installable and requires no soldering or permanent modifications to the synthesizer to install (other than perhaps a hole to mount a MIDI jack).  Provides MIDI In and Through capabilities on Channel 1-16.  Easy channel selection with the push of a button and the press of a key.  Easy to configure on which key the Omni notes start on your MIDI controller.

Order now!

Synthchaser MIDI Adapter for ARP Omni 1 & 2

I’ve made a video series chronicling a restoration I just did on one of the ARP Pro/DGX synthesizers I have for sale.  In the first part, I show what’s wrong with this keyboard and come up with a plan of attack:

 

In the second part, I give a technical overview of how the ARP Pro Soloist and Pro/DGX works:

In this part, I install the Synthchaser LED slider kit:

In this part I recap the keyboard and fix some of its issues.

In this part, I rebuild the Pratt Read keyboard and install a new aftertouch sensor, and get all keys working and feeling great. No more clacking keys!

In this part, I troubleshoot and repair the remaining issues in the keyboard.  Even after replacing the aftertouch sensor, some aftertouch effects weren’t working.  And some of the voices didn’t sound right.  So I whip out my oscilloscope and get to the bottom of it.

In the last part, I give a demonstration of the finished product working nicely, and show the features and settings of the Pro/DGX as well as run through the preset voices.

I received an ARP Omni 2 “for parts” that literally was in parts!  It came to me as a pile of boards.

Since it was complete, I decided to restore it slowly as time permits, recapping each board, inspecting for damage, etc…  This morning I got around to the Upper Voicing Board.  Someone had tried to fix a problem (likely a “stuck” note, caused by a shorted tantalum capacitor), but they lifted some solder pads and destroyed a trace while changing some diodes.

To correct the damaged trace between the diode and the resistor network, they soldered a 1W resistor to the board…  ARP PCBs are extremely easy to damage without proper soldering techniques.  They are not plated through hole, so it’s easy to lift solder pads, and more difficult to solder a component with traces on the component side of the board.  With some flux, and good soldering and desoldering skills, it is possible to work on these delicate ARP boards and have them looking pro when you’re done with them.

Here’s the same board with the 1W resistor hack removed, the board recapped (using the Synthchaser capacitor kit–pardon the shameless self promotion), and the diodes the previous person tinkered with also replaced.  Notice on the capacitors the smooth solder fillets on the component side of the board.  Because the boards aren’t plated through hole, it’s important that the solder joints on both sides of the board be solid!