MATRIXSYNTH: Ensoniq ESQ-1 Wave Synthesizer - w/ LED Sliders

Friday, July 14, 2023

Ensoniq ESQ-1 Wave Synthesizer - w/ LED Sliders

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via this auction

Pics of the inside below.

"This ESQ-1 has been completely overhauled and restored and features upgraded LED sliders. It includes an original Ensoniq ESQ-1 E2 PROM Storage Cartridge.

You're not likely to find another ESQ-1 for sale like this one any time soon. Yes, you might see so-called "professionally refurbished" synths out there, but none like this.

There were no compromises when it came to restoring this ESQ-1. However, I did not attempt to restore this ESQ-1 cosmetically, so there are nicks, light scratches, and other signs of age and use. Read on to see what was done:


This ESQ-1 has been completely stripped down, literally every part removed and thoroughly cleaned by hand.

For the body, buttons, and keys, I used hot, soapy water, brushes, cloths, and towels to remove all gunk and nastiness that built up over the years.

Every key was removed, cleaned, and if there were chips or holes they were filled and repaired.

The wires and contacts along the keybed were all cleaned and adjusted where necessary.

Every body part was removed and cleaned as described above - no body part was left in place before cleaning.

Each button was removed and cleaned, along with the display cover.

Old flux and grime and dust were all cleaned off the PCBs using appropriate solvents and cleaners. The jacks were all cleaned out. The cartridge port contacts were cleaned.

The pitch and mod wheels and mounting hardware were removed, scrubbed, and cleaned.

You can tell when something has been thoroughly cleaned from the look and the smell. This unit, while used, is as clean as when it was born in the Ensoniq factory; there are no funky smells and nothing is crusting away in a hidden cavity that can lead to future funky smells.


Aside from the keys mentioned above, where there was a busted or completely missing tab or screw standoff, it was repaired or completely refashioned with epoxy.

Any missing screws or nuts were replaced. In the case of the nut for the right audio-out jack, I created a nut because I could not find a replacement.

All wires redressed and remounted where necessary.

For some reason, this unit was missing the metal cover on the inside which is there to protect the main PCB and, I assume, help provide some shielding for the audio paths. I made a replacement (using one from another ESQ-1 as a model) out of plastic film and foil, not unlike what you'd find in Roland and (especially) Korg synths of that era.


This unit suffered from the dreaded dead screen. The repair involved a Display/Panel Controller Kit from Rainer Buchty and new clock crystal. In diagnosing the issue, I also replaced the NE556 and 74LS04 ICs.


The power supply board was completely rebuilt with all new capacitors and voltage regulators for reliability and stability.

Every electrolytic capacitor on all PCBs was replaced with a new one for reliability and stability.

ROM chips were upgraded to the latest v3.50 firmware.

All buttons cleaned.

New memory battery.


The original sliders were replaced with properly spec'd Bournes LED sliders with yellow LEDs. The slider caps are from Germany. A simple circuit was added to accommodate power to the LEDs in the sliders and provide a means of controlling the brightness. A trim pot is located under the top panel for this purpose. Simply remove the top panel's four screws, lift it open and there is the trim pot."

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