Category: ARP

I know what you’re thinking, but really, I do repair other brands of vintage synths other than ARPs!

In this video I rebuild the power supply and repair some other problems like tuning issues, broken trimmer pots, and hiss, noise and static in the output.

I recently restored and repaired a pair of ARP Pro Soloists that used to belong to Bernie Worrell and made some videos along the way.

In this first part, I take a look at the two keyboards, come up with a plan of attack to restore them, and begin disassembly.

In this second part, I troubleshoot the first of the two ARP Pro Soloists.  There’s a rather interesting problem, the notes are getting lower as you move up the keyboard!  Also touch sensor effects are dead and I get to the bottom of that.

In the third part, I repair some broken welds on one of the Pro Soloist cases with a two part epoxy.

In the fourth part, I disassemble and recap the second of the two Pro Soloists.  We fire it up, but we’re not as lucky as with the first one, so we troubleshoot and get to the bottom of the problem.

In this fifth part I repair the Voltage Controlled Filter.  The second Pro Soloist has a dead 4034 VCF submodule (the Moog patent infringing type), which unfortunately is sealed up.  We cut it open, excavate it out, troubleshoot and repair it.

In the last part of this video series I show you the final product–two Pro Soloists working great and ready to start making some funky music again!

 

I have the pleasure of being able to restore and offer for sale this early ARP 2600.  A true collector’s piece, this is one of approximately 35 produced “Grey Meanie” ARP 2600’s and is extremely rare!  It comes with the matching 3604 keyboard (not pictured).  If you have been looking for this rare piece of synthesizer history, please contact me while I am able to customize the restoration plan with your input.

I made this video which shows how to test the power supply of an ARP Synthesizer.  It was intended for someone with an ARP 2600, but I’m demonstrating with the power supply of a Pro Soloist, and the method shown can be used to test the power supplies in all models of ARP synths.  To do this test you just need a multimeter, the intended audience doesn’t need to be electronics wizards or even know how to use the multimeter.  If your power supply tests bad, I can repair it or supply a modern, upgraded replacement.

 

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!

In this video I have a String Ensemble in for repair.  The first step is to rebuild the power supply, which is actually spread over 5 different PCBs in the synthesizer!  In this video I show you around inside the String Ensemble, explain how the power supply works, what you need to do to rebuild it, and why doing so is important.  I show the failed components I pull out of the Solina and get it working again!

These kits are available in the store (pay attention to the revision of your Solina):

http://synthchaser.com/product/arpsolina-string-ensemble-v1-power-supply-rebuild-kit/

http://synthchaser.com/product/arpsolina-string-ensemble-v2-power-supply-rebuild-kit/

We are pleased to offer LED slider retrofit kits for ARP Synthesizers.  We currently offer kits for the Omni 1, Omni 2, Pro Soloist, and Pro/DGX.

These kits are user installable by anyone with reasonable soldering skills.  Even when they were new, the original CTS sliders just weren’t very good.  Compound that with 40+ years of use, dirt, and oxidation, even the most masterfully rebuilt CTS slider will feel terrible in comparison with these new, modern slide potentiometers.  The way these feel literally breathe new life into old instruments.

For people who just don’t like illuminated sliders, you can simply not connect them to power, and get the benefit of the improved performance without the lights.  For “purists” who like to retain the original look, it may be possible to install your original slider caps on the new potentiometer shafts (though we have not tried).

We have kits for other synthesizers like the ARP Odyssey coming soon, if you have a vintage synth that you would like to add LED sliders to and we do not have a kit listed in our store, drop us a line, we may be able to produce one for you.

http://synthchaser.com/product/synthchaser-precision-led-slider-upgrade-kit-for-arp-omni-1-or-omni-2-wcolor-options/

Synthchaser LED Slider Upgrade Kit for ARP Pro Soloist or Pro/DGX

 

The ARP Pro Soloist introduced in 1972 and continued through 1981 as the Pro/DGX featured selectable presets, which used 8 archaic ROM chips to control the routing of the signal path (filter resonance, vibrato, ADSR parameters, etc).  The ROM chip used was an Intersil IM5600, a 256 bit (!!) ROM that is long obsolete, and for which no compatible programmers are available today.

It has been long standing in the synth community that the ROMs are irreplaceable–once they go bad, one must be taken from another synth or the patient must be scrapped for parts.  This is no longer the case, Synthchaser has replacements available.  Contact us if you are in need of a replacement Pro Soloist or Pro/DGX ROM.

Update: ROMs may now be ordered in the Synthchaser store:

 

ARP Pro Soloist & Pro/DGX ROM