Repairing

A NiCd battery that has leaked in a Korg Poly-61, corroding traces and IC legs.

Two broken solder joints (left) and a delaminated PCB trace (right).

Failed electrolytic capacitors with swollen can tops and expelled rubber seals.

Repairing electronic music gear includes troubleshooting problems, replacing worn or damaged parts (both mechanical and electronic), repairing electrical connections, and performing preventive maintenance.

Prophet 5 rev. 2 missing a power transformer.

Essentials of electronics repair

Be Careful

Avoid causing more damage.

Be organised and take your time.

Start simple

Check easy-to-fix issues first.

External checks

Gather information on symptoms.

Check cables, power supplies and fuses.

Look for signs of physical damage.

Cleaning

Brush and vacuum the device with ESD-safe methods.

Remove contaminants e.g. from spilled drinks

Opening the device

Unplug gear before opening.

Use soft surfaces to avoid scratches, ensure any separated but still connected parts are well supported.

Find the service manual (these can have errors) or watch disassembly videos.

Use containers to keep screws and other fastenings from getting lost.

Take note of where any parts will go when reassembling.

Take detailed photos of the internal setup, you may need to refer to these later.

Initial observations

Check for battery leakage, physical deformities, and blown fuses, (look for the cause of any blown fuse).

Look for signs of overheating or smoke.

Connections between dissimilar metals can corrode or degrade over time.

Fixing process

Re-seating connectors can solve many issues. Be very careful not to bend any pins.

Check for corrosion and clean with contact cleaner.

Avoid fully removing socketed ICs fully; raise the IC slightly and push down again to clean the contacts.

Clean or replace scratchy pots.

Check solder joints and touch up if needed, (with matching solder type). Be careful not to damage any nearby wires plastic parts with the iron.

Common issues

Many problems are mechanical rather than electronic.

In industry when fixing is too time consuming a board is swapped rather than repairing the components.

Showcase

Practical, real-world examples to guide and inspire.

• Roland Alpha Juno 2

See also

Methods

• Electronic circuit fault finding
• Desoldering
• Recapping
• Replacing components
• SMT reflow soldering
• PCB repair

Further reading

• How to diagnose and fix everything electronic by Michael Jay Geier, McGraw Hill TAB, 2015, ISBN 9780071848305
• Troubleshooting and Repairing Electronic Music Synthesizers by Delton T. Horn, TAB, 1992, ISBN 9780830639212, (not recommended)
• Prophet 5 technical manual by Sequential Circuits

External links

• Synfo.nl, Synth service manuals, synth IC data sheets and links to synth technicians.
• Beginning pinball repair and circuit board repair, includes useful information.
• WarrantyVoid FAQ - keyboard & sound toy modification, circuit-bending, includes useful information.
• The Ship of Thesus, on whether to repair or to preserve vintage synths, Jon Dent blog, 1 Apr 2020
• The Most Common Maintenance Issues of 22 Classic Synths (and How to Fix Them), by Travis Thatcher, Reverb, Sep 2017

Forums

• r/SynthRepairs
• Synth Repair, Syntaur Forums
• Repair, EEVblog Electronics Community Forum
• Vintage Synth Repair And Mods., Facebook group

YouTube

About the general principles. For repairs to a specific piece of equipment, see its page.

• Synthchaser
• Musical Instrument teardowns and repairs by markusfuller
• DIY Guitar Pedals
• Mr. Carlson’s Lab
• mikeselectricstuff
• The Signal Path
• Jeri Ellsworth
• Fran Blanche
• channelengineer
• ElektronikLabor
• mjlorton
• Sala Science
• Learn Electronics Repair
• Uncle Doug
• CuriousMarc
• Marco Reps
• Jordan Pier
• Techmoan
• bigclivedotcom
• EEVblog
• DextersTechLab